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Be sure to read Part 1 of this series on arches: Circular-Based Arches

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This depressed type of arch, like the Segmental and Drop arch, can be used when the design requires the rise—or height—of the arch to be reduced. While segmental and ‘elliptical shaped’ arches both share a rounded top, the elliptical variation provides the benefit of a clean vertical transition, and respects traditional design principles.

A three-centered arch is an elliptical approximation using three tangent arcs. (Click any image to enlarge.)

A true ellipse is the shape created by making a diagonal section-cut through a cone or cylinder. The ellipse has two focal points and a constantly changing arc radius.

It can be difficult to determine if an arch is a true ellipse, or just one composed of simple tangent arcs, swung from three centers. Either way, elliptically shaped arches are more commonly found in traditional homes based on colonial styles—though their use depends more upon the skill of the architects, millwrights, and finish carpenters.

I’ve heard some carpenters say (and I won’t mention any names!) that the popularity of segmental arches—sometimes one of the most boring and ugly forms of architecture—results more from a lack of knowledge and technique than from an understanding of classical forms—both Gothic and Colonial.

These carpenters believe that elliptical arches—or, at the very least, three-centered arches—are far more attractive, but that the technique is beyond the skill of most contemporary carpenters. I don’t necessarily agree. I don’t think the segmental arch should be completely avoided.

A segmented arch forms a pleasing and handsome frame, as long as the arches (the rise, the radius, the span) are nearly identical in size.

In the first part of this series, I shared some images of segmented arches gone wrong. But, when designed and executed properly, a segmented arch forms a pleasing and handsome frame, as long as the arches (the rise, the radius, the span) are nearly identical in size. But, if the openings have variable spans, a three-centered arch is a better answer!

At this point, I can’t help but mention Gary Striegler’s article in JLC about building an arched passage door. I’m including a PDF of that article here. It’s a critical part of this study, both because it will help readers form a better understanding of complex arches (arches with more than two centers, and elliptical arches), and because Gary’s article provides techniques for constructing a three-centered arch, which is much easier than milling elliptical molding! In fact, mill shops often use a similar technique to create their elliptical moldings, sometimes using five or more centers to create a more accurate elliptical shape.

This coffered three-centered arch passageway features raised panels and uses the Ionic capitals of the pilasters as imposts to provide visual strength and support.

Another example of where a three-centered arch is easier on the carpenter, as opposed to a true ellipse, is in a coffered passageway. The curved panels of the head only require two different radii. In the photo to the right, you can see that the panels across the top share the same curvature, and panels with a tighter radius are used as the arch terminates on each side.

Getting back to the purpose of this article—how do we layout this pseudo ellipse? Well…it all depends on what you are given to work with. Although being involved at the planning stages is ideal, most of the time it’s not a reality.

Hopefully, the following Quick Reference Guides will help you deal with any ‘curve’ you’re thrown.

The Classic Three-Centered Arch

This layout is for the classic three-centered arch. You only need to know the required width or span of the arch. The rise of the arch will be determined by proportion only.

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Three-Centered Arches with a Known Height & Width

This layout is used when you must fit an arch within a predetermined height and width.

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Three-Centered Arches with Known Radii

This layout is used for creating a three-centered arch when the two radii to be used are predetermined. This is the situation used in Gary Striegler’s article.

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Keep an eye out for the last part in this series, on Four-Centered Arches!

Common circular-based arches (Note: Click any image to enlarge)

Arches in modern homes often seem slightly off—there’s frequently something wrong with them, particularly when you compare arches built in homes today to historic designs. I couldn’t put my finger on the problem, so I started researching arch designs in pattern books and on the Internet. What I discovered is more a problem of communication than technique. Mixing arch designs—like this segmented entry door jamb and 3-centered stone arch—never works (see photo, right).

Combining a group of openings with segmental jambs can look awkward if the spring lines are at different elevations, if the tops of the arches vary in height, or if the spans are significantly different (see image, below, click to enlarge).

Segmental Openings

And segmented jambs can look even worse if keystones are used improperly. Remember, you can only put a keystone in one and only one spot—at the apex of the arch (see “Parts of an Arch,” below).

And another thing . . . segmented radius arches do not look good when they’re decorated with classical head details. Doesn’t there appear to be something missing in both of the pictures below? Yes, there is—structural support and a defined point of termination.

Certainly, there are a lot of builders and architects who aren’t reading Get Your House Right! But the real problem I found was with instructions for laying out arches—they are all terribly outdated! In fact, almost all of the information we use today has been collected and re-printed from books that were published over a century ago—illustrations filled with confusing text, multiple lines and intersections, usually with all the information compressed into one ink drawing (see image, right).

Publishing books a hundred years ago was prohibitively expensive: the cost of a single sheet of paper was so high that private letters were often written with the text running in both directions, just to save on paper. It’s no wonder book publishers never considered multiple, step-by-step illustrations.

But that’s not the case today—at least not for an e-magazine like THISisCarpentry! Now that we have paper-free publishing, it’s time to re-draw those old instructions.

The articles in this series are meant to provide a richer format for today’s “digital savvy” carpenter. There is still a fair bit of geometry involved, but fear not! All of these articles include Quick Reference Guides, or ”cheat sheets” (downloadable PDFs), with step-by-step instructions for each arch layout.

Let’s get started:

Arch Basics

An arch is a structure that spans an opening and supports weight. Arches have been around for thousands of years, and were originally constructed out of stone. During the Roman Empire the engineering of the masonry arch was perfected and its structural element defined.

Even though decorative millwork doesn’t need to provide physical strength and support, it should do so visually. You can’t fool the eye. You might not know why, but something inside you will let you know if it doesn’t look quite right (just like the start of this next sentence!). It’s just like why choosing a terminating or supporting molding can make all the difference.

Parts of an arch (click to enlarge)

Important Terminology

Impost: The block set into a wall or uppermost part of a column or pillar, used to support an arch.

Keystone: A wedge-shaped piece at the apex of an arch that locks the structure together and allows it to bear weight. The shape of the keystone should always be related to the center point of the arc that makes up the arch.

Spring line: The line at which an arch begins—located at or above the impost.

Stilt: The elevation of the spring line above the impost.

Voussoir: A wedge-shaped piece used to make up the curved part of an arch.

Geometry Refresher

Because all of the following arch types are based on the circle, let’s review the fundamentals of circular geometry.

Anatomy of a circle

Important Terminology

Arc: A curved line that is part of the circumference of a circle.

Chord: A line segment joining two points of a curve.

Circumference: The distance around the perimeter of a circle.

Diameter: The distance across a circle through its center point.

Radius: The distance from the center point of a circle to its perimeter. Equal to one half of the diameter.

Point of Tangency (tangent point): The point at which the tangent touches an arc or circle.

Tangent: A line, arc, or circle that touches an arc or circle at only one point.

One-Centered Arches

Done correctly, segmental arches are versatile enough to even feel at home in a Craftsman style home.

Determining the radius of an arc for a given span and rise can be worked out with simple geometry, but if you have a construction calculator, you can find your radius with just a few key punches.

Here are the steps (I use BuildCalc on my iPad. If you use CMPro on your iPhone/iPad or Droid, the key locations are a little different, but steps are the same!):

1. Enter the desired span of the arch (48 inches in this example) and press RUN.		2. Enter the desired rise of the arch (6 inches in this example) and press RISE
3. Press the CONV key (when you press the convert key, the ARC key will change to the RADIUS key).		4. Press the RADIUS key to display the radius. (Note that at the completion of this calculation, BuildCalc's keys will revert back to their default settings. The Radius key becomes the Arc key again, as seen above.)

Finding the radius of a segmented arch

This function of a construction calculator can also be used if you need to find the radius of an existing inside curve.

1. Cut a straight piece of wood to a length that will fit inside the arch, and touch two points of its curve. The actual length of the stick is not important, but using a nice round number like 12 in. or 24 in. will make things easier. After cutting, measure and mark the midpoint along its length.

2. Place the piece of wood against the arch—it doesn’t matter where.

3. Measure the distance at a right angle from the top of the stick’s midpoint to the existing curve.

4. Enter that measurement into the calculator and press RISE.

5. Enter the length of the stick and press RUN.

6. Press the CONV key to change the ARC key to the RADIUS key.

7. Press the RADIUS Key.

For readers who don’t have a construction calculator, here is the formula you can use with a standard calculator. Unfortunately, you also have to convert any fractions to decimals.

Two-Centered Arches

While Roman architecture is known for one-centered arches, two-centered arches are fundamental to Gothic architecture and form the simplest “pointed” arches.

The large main parlor window at Lyndhurst is framed by a two-centered arch.

The lancet windows surrounding this tower are typical two-centered arches. The same motif repeats itself in a crenelated pattern across the porte cochere parapet walls. (Sells Mansion, Columbus Ohio)

Variations

There are many variations of two-centered arches, and each depends on the location of the center points. When the center points are located closer to the middle of the span, the arch flattens out; if the center points are located farther away from the middle of the span, the arch becomes sharper.

The drop-arch on this fireplace, beneath a suspended hood, provides just the right amount of gothic flavor for an early 20th century arts-and-crafts home. (www.adamsonhouse.org)

The following Quick Reference Guide provides step-by-step procedures for finding the required arc centers and appropriate radii for a two-centered arch that must meet a specific height and width.

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Note: A recurring step found in these geometric constructions is to draw a line perpendicular to another line’s midpoint. For simplicity, a square has been used in the illustrations, but the task can also be accomplished with just a compass/trammel and a straight edge, as shown in the following Quick Reference Guide.

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Don’t miss the next article in this series on Three-Centered arches, where the geometry gets a little more complicated.

Chairs and chair rail may sound like they have a lot in common, but the relationship is limited to their approximate heights. Chair rail is the most misused and abused molding in new houses today. But it is also the easiest molding to install correctly, and one that can do the most to make a house feel like a home.

Yeah but…

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What? You want to argue the point? You still think chair rail should always sit at 36 in. from the floor? Sorry, there is no standard height dimension. In fact, historically chair rail started out very low.

Even in colonial rooms with 10-ft. ceilings, I’ve seen chair rail set at 30 in. from the floor. There are some 18th-century pattern books that show the chair rail at 24 in. off the floor. In fact, in rooms with 9-ft. to 10-ft. ceilings, this height is actually most appropriate for chair rail, and best falls within the rules of classical architecture (see photo, right). Over the past 60 years we have forgotten a lot about those classical rules, and we’ve forgotten how chair rail functions in a room.

A matter of scale…

Let’s back up a bit. Chair rail is a molding, right? The purpose of molding is to establish proper scale and proportion in a room. And because of its close proximity to us (chair rail is often the nearest horizontal molding we see) chair rail can do more to make a room feel right than either the baseboard or the crown. But get the chair rail wrong, and the room feels wrong—I can guarantee it.

Here’s where proper proportion comes into play. All of the classic architectural orders—the Tuscan, the Doric, the Ionic, the Corinthian, and the Composite—have strict rules of proportion. These rules of proportion were specified back in the first century BCE by Marcus Vitruvius Pollio, a Roman architect and engineer. Vitruvius used “modules” to ensure proper proportion.

He started with the spacing of the columns on a Greek temple, using that distance as a “module.” According to his instructions for achieving symmetry, harmony, and proportion, the base of a Doric column should be two modules and the height should be fourteen modules. That boils down to a proportional relationship of 1:7 — a column that is seven times as tall as it is wide. Put simply, if the base of the column is 10 in. wide, it should be about 70 in. tall. Of course, not all columns follow that same proportional rule.

How does all that relate to chair rail?

Ironically, the rules of classical architecture are really based on human scale, on the male body, and I’m the perfect classical specimen: My foot measures 11-in. long and I am 77-in. tall; a 1:7 ratio. Wow! (I pity you poor short carpenters with big feet!!!).

The moldings in a room are supposed to relate to our bodies, too. That is why you can walk into an old building and it just “feels” right. The reason it feels right is because it is symmetrical and harmonious to our own size. (See Fig. 1, below) We innately relate to and enjoy a space we fit into and fit well with.

Dig a little deeper and we find proportional rules for every architectural detail. Despite its name, chair rail actually corresponds to the molding at the top of a column’s pedestal.

Fig. 1

According to Abraham Swan, the Doric order didn’t even have a base because Vitruvius said: “This order is like a strong and robust man, such as Hercules, who was never represented but with his feet bare.”

Yet many later architects have included pedestals. For instance, when using a pedestal, Asher Benjamin divides the entire height of the Doric order into 80 parts. The diameter of the column equals six parts. According to Benjamin, the pedestal should be “two diameters and thirty minutes high.”

What’s all this mean to a carpenter?

Here’s how I look at it: Take a room with a 10-ft. ceiling, which is 120 in. Divide 120 in. by 80 parts. Each part would equal 1 1/2 in. Therefore, the column should be 9 in. to 10 in. in diameter (six parts). Multiply the column width by 2 1/2 to determine the height of the pedestal: 22 1/2 in. tall. Benjamin also suggests that the pedestal should be 15 parts high. Either way, the result is the same. Obviously, unless chairs were much shorter back then, the height of a chair has nothing to do with the height of the chair rail!

Wait a minute! Don’t leave the room yet! I’m not finished. We’re just getting started. Now we need to find out the exact size of each molding, from the plinth or baseboard, to the chair rail. Benjamin doesn’t provide that detail, but William Pain does in his 1778 book, The Practical House Carpenter.

Until the 1920s and 1930s, pattern books, like Pain’s, were used by carpenters and architects to duplicate classical details—and that means all molding profiles and proportions. But pattern books seemed to go by the wayside as minimalism and modern styles reduced the importance of moldings, and finally production trumped design. It’s no wonder that we so often hear from carpenters with questions about molding profiles, placement, and proportion. None of us were trained on the use of pattern books. And very few of the architects we work with are familiar with them. But that doesn’t mean we all can’t learn.

According to Pain, for a Doric pedestal, we start by dividing the height of the column into thirteen equal parts, where one part equals the diameter of the column. The height of the pedestal is set at 2 diameters and forty minutes, or 2.66 parts. For a room with a 10 foot ceiling, one part would equal 9 1/4 in. Forty minutes would equal about 6 3/16 in. That puts the pedestal about 24 11/16 in. from the floor. Let’s make it simple and add 1/16 in. Trust me. No one will notice.

Going back to William Pain’s book, we next divide the diameter of the column into 12 parts (9 1/4 in. ÷ 12 = 3/4 in.)

Pain then instructs us to divide one of those parts into 5—so 3/4 in. ÷ 5 = 1/8 in. (Well, not exactly, but it’s close enough for our purposes. Besides, that gives us a nice easy number to work with!)

Now let’s look at the three moldings that make up a traditional chair rail, and the sizes that Pain recommends for each one.

The cavetto, or cove molding, at the bottom should be 4 parts, which makes it 1/2 in., plus another 1/8 in. for the fillet above. The ovolo, or supporting molding, in the middle (sometimes this is an egg-and-dart profile, or a dentil molding), should be 6 parts, making it 3/4 in.; the corona at the top should be a bit more than 6 parts (I can’t read that number!), so let’s make it 7/8 in. (what the heck). There’s a fillet above the corona, and I can’t read that number either, but hey, it looks like 3/8 in. to me. Add all those crazy numbers together and we’ve got a chair rail that’s 2 5/8 in. No big surprise there, huh?

Too low is better than too high

The classical rules of architecture are the key to the proper size and placement of moldings in a room. Benjamin uses a slightly different set of proportional rules than Pain. But the overall effect remains the same. In the classically proportioned room, not only do we relate to the space, but the parts and pieces also “speak to” and relate to one another, from the crown to the base to the casing to the chair rail—and ultimately to us. Especially if weren’t not short with big feet.

When it comes to chair rail, I always advise customers to err on the side of too low rather than too high. Installing the chair rail or wainscot too high (see photo, right) diminishes the size of a room, making it feel uncomfortably squat and stuffed, kind of how you feel after eating Thanksgiving dinner.

Height isn’t the only problem we encounter when we install chair rail. Probably the biggest problem isn’t where to start it, but how to stop it—how to terminate, or resolve, the chair rail into casing, stairs, and other moldings. Here are some simple rules:

Never back-cut the chair rail at door or window casings.
Always butt cut the rail. If you’re running a build-up of stool and apron, notch the stool over the back of the casing, then butt cut or self return the stool; resolve the apron into casing.
Installing a backband is sometimes the best solution for terminating deep chair rail profiles.
Always install skirt boards on steps, even if there’s only one riser, otherwise, running the chair rail down the elevation change looks stupid.

Never interrupt the casing with the chair rail or with wainscoting! The casing is supposed to resemble a classical column, and should run uninterrupted from the floor to the top of the doors.

If you’re in complete control of a job, try to install the windows so that the window sills are the same height as the chair rail. But if the window sills are 40 in. from the floor, forgetaboutit! Run the chair below, and remember: it’s better to err on the side of too low rather than too high!

What’s a story on etched glass doing in a carpentry magazine? Good question. I don’t know the exact answer. All I know is that every aspect of construction interests me, and when I met Donna Burrows and visited her studio, I knew that other readers would be interested in seeing what I saw. Maybe it’s something about craftsmanship.

Donna is an both a craftsperson and an artist. You can tell by the way she moves her hands—quick, sure, continuous strokes with a razor knife following lines I barely see; and what she does with a sandblasting nozzle…well, watch the video at the end of this article and you’ll know what I mean.

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But it’s what she sees before one grain of sand touches the glass that makes her an artist—each layer of the finished piece, the same way a roof cutter or a stair builder visualizes a finished product when they’re looking at nothing but air.

Parrots for Privacy

Donna is the type that excelled in art classes and made the rest of us feel clumsy and useless. She’s been working glass for more than twenty years. I followed her through one job, from the client meeting through conception and completion. Her customers had recently removed a tree that provided privacy from their neighbors, but which also blocked their view. They wanted a partially-etched glass panel to put both their neighbors and themselves at ease. They weren’t really sure what kind of design they wanted, but they were fond of parrots.

These folks were fond of parrots. They had a collection of life-size sculptures in the trees of their yard, and glass parrots inside their home.

Drawing and tracing

Donna begins each project with a conceptual drawing. On some projects she’ll spend days on the drawing.

Once that’s approved, she enlarges the drawing onto a sheet of tracing paper, using a wall projector, to the exact full size of the finished panel.
It’s a low-tech process—she moves the projector back and forth from the wall until the size of the projected image matches the final dimensions of the glass panel.

The full-size drawing is also submitted for approval, and then Donna goes to work. She darkens the graphite lines on the tracing paper so they’ll transfer cleanly to a sheet of pressure-resistant self-adhesive vinyl. It’s that sheet of vinyl that plays the most important role in the sandblasting process.

	The pressure-resistant vinyl is applied to the glass, and then the drawing is laid on top and secured with masking tape on the edges.
	To secure the tracing paper in the center of the panel—so it won’t move even a fraction of an inch—Donna cuts out small triangles in empty areas of the drawing, then places a small piece of masking tape over the cut-outs.

Transferring the drawing is a simple matter of tracing over the back of the paper with a soft-lead pencil, which won’t tear the paper but transfers the lines to the vinyl. Donna lifts the paper frequently, checking that the tracing is complete, with each line crisp and clear.

Surgical Prescision

Sandblasting is an art, especially creating a three-dimensional image from a two-dimensional drawing. Each layer must be blasted in precise order, so that each overlapping line creates the impression of three dimensions.

Donna starts by marking the drawing in layers. Parts of the drawing must overlap other parts—some leaves, limbs, and feathers must lie behind other leaves, limbs, and feathers. The lower leaves will be shot by the first blast of sand. To keep the layers straight in her mind, Donna marks each first-blast detail with an X, then follows the traced lines with an X-Acto knife.

She changes blades frequently—the vinyl dulls the blades fast. What would take most of us hours, Donna does in minutes—handling the blade with practiced skill. Rather than twisting her wrist, she twists the knife in her fingers—her hand operating like a CNC machine—and follows the tracing without straying from the lines more than 1/32 in. Before moving the glass to the spray booth, she removes the first layer of vinyl.

Delicate Sandblasting

While it seems like a contradiction, in Donna’s hands, a sandblasting “siphon” gun is a delicate tool. She uses it for shaded glass, and for etching and shading on delicate areas of carved-glass designs. There’s a big difference between shaded glass, etched glass, and carved glass.

For shading, you don’t hit the glass straight-on with the gun, and you don’t just pull on the trigger like driving a hammer drill. If you don’t handle the gun with care, you can’t control the effect of the sand. It takes a lot of practice, but eventually you learn to blend the blast using a swiping-technique, hitting the glass from an angle, with 10 lbs. of pressure for small delicate areas and up to 40 lbs. for bigger areas. Like we feather the trigger on an impact driver, Donna feathers the trigger to adjust the blasting pressure.

When Donna carves glass with the siphon gun, she increases the pressure to 60 lbs., but that tool is for delicate work. For deep carving, Donna switches to a pressure pot system, holding from 100 to 300 lbs. of sand, run at about 80 lbs. of pressure, with a straight nozzle, just like a fireman’s hose, without any trigger. Controlling that beast takes real talent.

“You have to dance with it,” Donna says, “like T’ai Chi. You have to keep the flow going without stopping, without hesitating, without hitting one area too much. I’m only allowed to cut tempered glass up to 1/8 in. deep, and a lot of my work is on tempered glass because my panels are installed in doors, sidelights, and in large windows that come within 18 in. of the floor. But with annealed glass, I can cut as deep as I want…well, almost. For a 3/4-in. table top, there’s no code. To really carve glass, including tempered glass, there’s no better tool for the job.”

Outfitted with a full jumpsuit, external air-fed respirator, and hood—through which she can barely see—Burrows sprays the glass with a fine stream of silicon carbide or aluminum oxide at 120 grit.

“The sand I use is similar to sandpaper. You could use 80 grit or 60 grit, but that’s like cutting a corner. You need to go slow and control the sand, otherwise the result is not pretty. You want a beautiful, fine finish.”

For the first blast, while hitting the edges, Donna moves the gun in to within 4 in. of the glass, but sweeps out as much as 16 in. to the point where she’s barely blasting the glass at all because of the distance between the gun and the glass.

Remember, the glass is etched in layers—with the edges of overlapping areas hit harder for more emphasis. But Donna handles the gun with care, angling the stream away from the first layer and controlling the blast so it doesn’t diminish the fine finish of each leaf.
Here you can almost see the blast of sand leaving the nozzle of the gun and etching a fog-like pattern into the glass.
For delicate and intricate details, Donna brings the nozzle right to the glass.

Once the first “layer” is blasted, Donna removes the next “overlapping” layer. The lines created by each layer quickly develop into a two-dimensional work.

Donna found this scratch in the glass while she was laying out the drawing. Sometimes the sign of a good carpenter is knowing how to fix problems. Donna has that “carpentry” approach to her work, too. There’s always a fix, if you plan ahead. She hid this scratch in the second layer of a leaf.

With parrots on the windowsill, the finished etching fits perfectly in the clients’ home, providing just enough privacy from the neighbors without blocking the view.

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As drawn, the jig should handle casing from 2 1/2 in. to 5 1/2 in.

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The setup, as I envision it, would use two templates, and a template base, for each part of the joint, the leg and the head. These parts should be precision-cut, either on a mill, or with a CNC router. The rest of the jig would be shop-made from available materials.

The templates could be made of 1/4-in. melamine, plastic, or possibly 1/8-in. aluminum. The template bases could be made of 1/2-in. melamine or plastic, or 1/4-in. aluminum.

Let me say here that the drawings are done from theory, and may require minor adjustments to provide a tight joint after the first set has been cut and tested. The templates are based on using a bit and bushing setup, and require a 1/16-in. margin in the template. I used a 1/2-in. bit with a 5/8-in. bushing.

The templates use a 1/16-in. margin for the bit and bushing setup. I used a 1/2-in. bit in a 5/8-in. bushing.

Now for the shop-made parts, and the setup of the jig.

We’ll start with the leg jig, which is the easiest. As my drawings show, the base can be made of plywood, MDF, or another flat material. The guide is 1/4-in. thick, and is shown as one piece in the drawing, but it would probably be better as three pieces with the head stop separate. These pieces would be sacrificial, and could be screwed to the base once they have been aligned in the jig. The part that I call “the receiver fence” should be cut to accommodate the height of the casing under the template base.

Shop-built base for the leg jig.

The template base is screwed to the receiver fence, and the templates fit into the base recess. The recess would be milled to allow the template to sit just proud of the base so there will be nothing to bump the router. You will notice the corner radius is different on the top and the bottom, so the templates will only fit in one direction.

...the corner radius is different on the top and the bottom, so the templates will only fit in one direction.

The casing legs are cut square and milled face up in the jig. The left leg is placed against the left guide, and the right leg against the right guide. The templates are flipped over to make the opposite hand-cuts. The first cut template will cut the dado on the miter and the rabbeted area. The second cut template will adjust the height of the pin that fits in the dado cut in the head piece. Of course, the second cut will require adjusting the plunge depth of the router. Keep in mind that the template is not in contact with the workpiece, so any wobble will affect the cut.

The head jig is a little more complicated, but only for the initial setup of each casing. The head piece should first be cut to size with the appropriate miters. It will be milled face down and centered in the jig. The head jig is made like the jig for the legs, with the following differences: The left and right guides should be adjustable, and the head stop cut with a 90 degree angle. The head stop should be placed with the point at the exact center of the jig. Once it is properly adjusted, the head stop should not have to be moved.

Shop built base for the head jig.

To cut the head piece, the molding is centered face down in the jig. A custom shim will have to be used for each casing profile in order to support the thinner side. The back side of the casing must be absolutely level with the jig.

A custom shim is used to support the head casing during milling.

Since the rabbeted area on the head piece will change when using moldings of different width, you will have to place the casing in the correct position for the first cut. The short point of the miter should be aligned with the template (1/16-in. from the template edge), so the shoulder of the rabbet is cut to this point. Measure the perpendicular distance from the head stop to the miter, and make a right-angle or chevron shaped spacer block to that dimension.

A custom spacer block should be cut for each molding width used.

The spacer block is only used for the first cut. It is removed, and the work piece pushed against the head stop for the second cut, which will be the dado cut in the head piece. Again, the templates will flip to make the opposite hand cuts.

The second cut is made with the molding placed against the head stop.

Different casing depth and width would dictate the four cutting depths on the router; however, once set on a plunge base this should not be a problem. If I were doing a lot of this work, I would probably make a setup block with those depths for future reference (or use multiple routers). The use of a plunge base would also allow you to step the first cut, which could be pretty deep, especially on the leg piece.

This is just my concept. I don’t believe that this joint would appear in a tract house, but possibly in a custom house with a lot of trim. I think the initial setup could be made in the shop, and the jigs would be compact enough to go to the job site. Of course, the operator would have to be sharp enough to select the right cutting depth, and to stop the head piece dado cut before it hit the face of the casing.

I’m sure you will all let me know what you think, and your comments will direct where it goes from here. Since I’m mostly retired, I don’t have a need for one of these, but I do enjoy making jigs and trying to solve the problems!

(Illustrations by Wm. Todd Murdock)

———

AUTHOR BIO

Svend immigrated from Denmark to California in June of 1958. During the latter part of a three-plus year stint in the army, he worked part-time for a general contractor in northern California. The job turned full-time after he completed his time in the service.

After moving to the Palm Springs area, he worked in several different trades, starting a Masonry and Concrete business with a partner in 1975. He obtained his general contractor’s license in 1979, and in 1980 changed the business model to pre-cast concrete, commercial, and industrial general contracting. When the partnership dissolved in 1995, Svend had an opportunity to build a high-end custom home for a friend. That job led to building more custom homes in the same country club, which lasted for twelve years, until his recent retirement.

Svend enjoys woodworking, metalworking, and all projects that involve creating something with his hands. He also enjoys a tennis game once or twice a week.

I was in the midst of trimming out a recent remodel when one of the guys described a miter joint he’d noticed while doing the demo work. What he described sounded more like a Japanese temple building joint than the conventional miter joint found in your typical American house. I was intrigued. When he found a sample of the joint and showed it to me, I was amazed.

What we were looking at was a true “lock miter.” (Click images to enlarge)

The leg casing was cut square across the top, then rabbeted at a miter, with a deep dado right against the miter. The head casing was mitered and cut with a corresponding dado that locked right over the leg.

Here in my hand was a miter joint that, although obviously made by machine, was pure elegance. I began to imagine the glorious accolades I would receive if I could reproduce that joint. My mind was swimming with thoughts of fame and glory when it gradually dawned on me that making this joint on site was not going to be easy. The tolerances had to be very tight (indicating a dedicated setup), and I would have to be able to do it for right and left miters (indicating two dedicated setups).

If I was going to solve the mystery of this joint, some research was in order.

The casing had a stamp on the back side that said “CURTIS 1866″. So I did a little digging on this company. My own research, along with some catalog pages provided by Brent Hull, confirmed that what we were dealing with was the Curtis Millworks Mitertite Joint. As it turns out, the Mitertite Joint was only one of several innovations Curtis became known for.

Charles Curtis actually started out in the grocery business. In 1866 he and partner W.G. Hemingway bought a controlling interest in a firm which ran a small door and sash factory. By 1868 Charles and his brother George Curtis had bought a controlling interest in the firm, which became known as Curtis Bros. & Co.

When George joined the team, one of his first ideas was the introduction of factory glazed windows. Previously, window sash was produced without glass, and a builder had to glaze the window on site. Pre-glazed windows were a pretty risky venture, but the gamble sure paid off. Today, if a window came to the job site unglazed we would stare at it in disbelief!

Another interesting innovation can be credited to Judson Carpenter, an uncle who became the company’s purchaser. Judson introduced the idea of grading lumber used in the shop. The same principles he introduced at Curtis Bros. are still used in lumber grading today.

As time went on, Curtis Bros. focused on streamlining their manufacturing practices and standardizing production at each of their factories. Steel gauges and templates were employed to ensure a product’s uniformity regardless of where it was manufactured. This uniformity meant that parts were interchangeable and replacement parts were easy to procure.

All of this progress eventually led to the development of the Curtis Silentite window. According to Brent Hull, the Silentite double hung window represented the “first major improvement in double hung wood windows in 300 years….”

These improvements came courtesy of the Curtis research department created in 1925. This same department also came up with a proprietary chemical treatment to help prevent wood decay. It was here that the Curtis Mitertite interlocking miter joint was born.

As you can see from the drawings below, this joint locks together tightly and requires no glue. The sample I have has no glue in it at all, and it looks great—tight when closed. In fact, the miter joints we found in the house I was remodeling have not opened in 60 years.

	From the top, you can see the dado joint.
	But from the face the miter can’t open, even without glue.
	The rabbet and dado lock the miter together.  The Curtis Mitertite might be the perfect joint for dramatic humidity swings, if we could just figure out a way to cut it that meets OSHA requirements!

I would really like to recreate this joint myself. Unfortunately, I have not been able to find any documentation describing the process used to manufacture it. Curtis was undoubtedly one of the most innovative woodworking companies in history, but either they kept their trade secrets close to the chest, or they have simply been lost in the dustbin of time.

Fortunately for us, this is exactly what a magazine like THISisCarpentry is all about, right?

I’d love to hear suggestions and comments about how this joint could be reproduced on site, or in a modestly equipped shop. Preferably with one setup producing both left and right miters.

So, what are your ideas, fellow carpenters? Can we come up with a way to recreate this joint?

———

AUTHOR BIO

Dave Parker has worked in the building trades for most of his career, with a focus on trim carpentry and architectural woodworking. At work he enjoys nothing more than a technically challenging project. At home he enjoys time spent with his family at the beach or in the snow. A graduate of The College of the Redwoods Fine Woodworking program, he currently produces millwork and high end furniture from his shop in southeast Michigan.

If you are tired of working out trim details on a scrap of wood or making shop drawings with graph paper and a ruler, SketchUp is your answer. Unlike most computer-aided design programs you may have tried, SketchUp is very intuitive and works the way a carpenter thinks.

SketchUp has a simple set of tools that you can use to create anything from a rough mock-up to a very detailed drawing with 1/64″ precision. How much detail you want is up to you. The ability to convey your ideas to customers quickly and to produce working shop drawings is what SketchUp can do for you. Are you intrigued? What if I told you that it’s FREE!

It’s true. SketchUp is 3-D design software available from Google. It is currently available in two versions—SketchUp 7, which is absolutely free, and SketchUp 7 Pro, which is not. The free version of SketchUp has all the power of the Pro version with the following few exceptions.

SketchUp 7 Pro includes:

Layout – additional software that works with SketchUp and allows the user to import drawings from SketchUp to create various types of presentations. You can incorporate title blocks and use standard sheet sizes for printing.

Style Builder – additional software for creating custom drawing styles.

Additional Exporting Options - PDF, DWG, DXF, as well as various vector formats.

Creation of Dynamic Components – used to make components that are interactive, such as moving doors and drawers, and to make components that will rescale or replicate, such as fence pickets or floor tiles. These components will work in the free version, but can only be created in the Pro version.

SketchUp 7 Pro currently retails for $495. A student license is available for just $49 a year to anyone who is currently enrolled in an accredited school and has an .edu email address. The terms of a student license, however, forbid commercial use. Both versions can be downloaded from http://sketchup.google.com/download/.

Before you download the software and get to work, make sure your computer’s hardware is adequate. The hardware requirements to run this program should be “no sweat” for most new computers. This link should answer any questions you may have.

http://sketchup.google.com/support/bin/answer.py?answer=36208&cbid=-x534j6yf9529&src=cb&lev=topic

The one thing Google lists as “recommended,” that I feel is ESSENTIAL, is a three-button, scroll-wheel mouse. Without this very inexpensive add-on, I can promise you nothing but frustration. Navigating in a 3-D drawing is almost impossible without one.

Drawing your way:

Once you have installed SketchUp, you have the opportunity to customize it to the way you work. SketchUp is used by architects, engineers, and designers, as well as carpenters. Different units of measurements and levels of precision are available as preset templates for the type of work you do. The first screen you see after installation will look like this. Note that tutorials are available from this screen. They are excellent for the general user.The button labeled “Choose Template” will give you  an opportunity to select the type of drawings you plan to do and will  load SketchUp with those settings every time you launch it (circled in red on right).

The template that will probably be of the most use to a finish carpenter is the “Product Design and Woodworking – Inches” template (circled in red on right). It is a 3-D template with the units of measurement set to fractional inches. The template for metric units is also available just beneath it. This is a good place to start, and as you become more familiar with the program, any personal preferences you decide to change, such as unit precision, background color, styles, etc., can be saved as a new template with a unique name.

One thing you might want to consider changing right off the bat is the unit precision in this template. It is pre-set at 1/64″. For most work, I keep the precision at 1/16″. If I’m working with veneer core plywood, I will dial it down to 1/32″ precision to get more accurate shop drawings (I still take actual measurements in the shop before I cut anything!). It is also a good idea to check the box labeled “Enable Length Snapping.” These options can be selected from Windows>Model Info, under Units.

Once you have your new preference set, create a personal template by going to File>Save As Template.

Getting your tools in order:

These are not the only tools available—just the selected tools by Google for “Getting Started.” By going to View>Toolbars, you have the ability to turn on or off the toolbars you want available. The toolbar setup I prefer to have available looks like this.

This is only my preference and what you will see in the following video tutorials.  As you become more familiar with the program and all of its different tools, you may find that a different tool suite suits your work better.

Keyboard shortcuts are great timesavers for the most commonly used tools. Instead of moving your cursor back and forth from the drawing window each time you want to select a new tool, new tools can be automatically selected by pressing an assigned key on your keyboard. If you click on the “Tools” menu at the top of the screen, a menu with a list of frequently used tools will appear. To the right of the tool name will be the assigned keystroke. A list of all assigned shortcuts can be found under Windows>Preferences>Shortcuts. There you can change any shortcuts or create new ones.

SketchUp Quick Reference Card

Many of SketchUp’s tools also have multiple functions. By hitting a modifier key on the keyboard, the selected tool will perform a different task.

You are probably starting to worry that there is too much to remember. A great help is the quick reference card that Google has available for download at: http://sketchup.google.com/support/bin/answer.py?hl=en&answer=116693

I highly recommend printing a copy of this PDF to keep handy as you start to learn SketchUp. I even laminated mine!

Navigating in 3-D:

In order to draw in 3-D, you must first understand how to navigate through the three-dimensional world of Sketchup. There are three colored axes in a SketchUp model—red, green, and blue. The blue axis is your vertical “plumb line.” The red and green lines are both “level” and run at right angles. These axes all meet at the origin. Understanding this important concept is half the battle when it comes to drawing your masterpiece.

Although all of the navigation tools are available from the toolbar and through keyboard shortcuts, using your three-button scroll-wheel mouse is the only way to draw efficiently.

	Zoom – By rolling the mouse wheel forward, you can zoom in for a closer look at the detail under your cursor. Roll the wheel backward to zoom out again.
	Orbit – Pressing down on the scroll wheel will allow you to pivot your point of view. By holding down the scroll wheel and moving the mouse left and right and forward and backward, you can orbit around your drawing to change your perspective.
	Pan – Holding down the shift key while “orbiting” with your mouse will allow you to slide your current view in any direction. This can be helpful for moving quickly to another part of your drawing.

Helpful hints:

• When zooming in or out, place you cursor over a part of your drawing instead of the background. This will speed up the process since you are zooming from a specific point and not a point in space.
• Use “Zoom Extents” on the Camera Toolbar to find yourself when you get lost in the details.
• Don’t overlook the “Pan” tool. Sometimes it’s the fastest way to get to where you want to be.

Drawing 2-D shapes:

Unlike a house that is composed of thousands of different components, a SketchUp drawing is only made up of two things—edges and faces. An edge is really just a line. When you close a loop of at least three edges (in the same plane), a face will be automatically created. The face is like a skin connecting all the edges. You can think of it like the canvas an artist might stretch across a wooden frame, and like a canvas, those surfaces can be “painted” with colors and textures to give your model a more realistic look.

With the very simple set of drawing tools SketchUp provides, you can easily create complex shapes with precision. (Shortcut keys are in parentheses.)

	Drawing Toolbar- Use the rectangle (R), line (L), circle (C), and arc (A) tools togetherto create new shapes.
	Undo – Use this to back up through your previous operations.
	Eraser (E) – Use this tool to erase unwanted edges.

Measurement Toolbar or MTB- Use the MTB, located in the bottom right corner of the screen, to give precisemeasurements to the lines and shapes you draw

Inferring – This is an internal part of SketchUp and is always available. It allows you to use points in your drawing as a reference when creating or moving new objects.

Helpful hints:

• The perspective of your view tells SketchUp which plane you want to draw in. Using an elevation or the plan view is a quick way to give SketchUp the “hint.”
• Use the inferred snapping points along an edge to quickly draw objects with precision.
• When entering numbers in the MTB for a rectangle, the length along the red axis is entered first. If the rectangle isn’t aligned with the red axis, the blue length is entered first. There are exceptions to this rule that will be covered later.
• To recreate or “heal” a face, redraw any of the face’s edges.

Drawing 3-D shapes:

The magical part of Sketchup begins when you start to extrude 3-D objects from the faces you have created. The intuitiveness of SketchUp’s patented “push/pull” technology not only makes it easy to learn but also fun to use.

	Push/Pull (P) – Like its name implies, this tool allows you to push or pull on a selected face to add or subtract volume from an object.
	Select Tool (Spacebar) – Use this to select objects for modification in your drawing.
	Move (M) - Use this tool both to move and to copy selected objects.
	Rotate (Q) – Use this tool to rotate a selected object around any axis you choose.
	Follow Me - Use this tool to extrude shapes along a path, including around corners and curves.

Helpful hints:

• Inferring to parts of your drawing while using the Push/Pull tool or the Move/Copy tool is a quick and accurate way to set dimensions.
• Double-clicking a face with the Push/Pull tool will repeat the last push/pull operation.
• Pre-selecting a path for Follow Me is faster and will often give better results.
• Creating a “selection box” by drawing a box with the Select Tool from left to right will help you select objects quickly. This will select every edge and face that is completely bound by the box. A box drawn from right to left, on the other hand, will select everything in the box as well as any line and face the box crosses.
• The Move Tool is in “copy mode” when a “+” appears next to the cursor icon. This is toggled on and off by pressing the Ctrl key (Use the Option key on a Mac).
• To move objects in an axis direction, use the arrow keys to lock the movement of the Move Tool. Pressing one of these keys will toggle the lock on and off.

↑or ↓ for the blue axis (remember: the blue axis runs up and down)

→ for the red axis (remember: right for red)

← for the green axis (remember: it’s the only one left!)

Putting it all together:

With the basics under your belt, it is time to apply them to a “real world” project. Using the previous tools and techniques, some tools from the Construction Toolbar, and an introduction to “Groups” and “Components,” we will put together a simple bookcase.

	Components (G) – An entity of edges and faces (or other components) that are separated from other objects in the drawing. All instances of a Component are automatically updated by editing a single copy.
	Groups – An entity of edges, faces, or components that are separated from other objects in the drawing.
	Tape Measure (T) – Use this tool to create guidelines and points to help layout and place desired objects.
	Dimension – Use this tool to display dimensions in your drawing.

Helpful hints:

• When creating a component, make sure the box labeled “Replace selection with component” is checked.
• When drawing rectangles connected to endpoints or on the face of another object, the dimension entries in the MTB will list the longest dimension first.
• Use Flip along from the context menu to create mirrored copies of objects.
• Use the Outliner to hide and unhide groups and components in your drawing to view details.
• When using Follow Me on a group or component, make sure to draw the path within the group/component by double clicking on the entity to edit it.

When you are finished with your drawing, you can save it by going to the File menu and choosing Save. You can choose to share your drawing in several ways. You can print the current view in the drawing window by selecting the Print option from the File menu, or you can create a JPEG file from the File>Export> 2D Graphic option. The JPEG file that is created can be printed or sent in an e-mail. You can share the 3-D version of your drawing by sending the saved SKP file to anyone who has SketchUp on his or her computer. Clients can easily view your designs in 3-D with the SketchUp viewer available from Google’s SketchUp website. This software only allows users to view the drawing, they cannot edit it! http://sketchup.google.com/download/gsuviewer.html

Honestly, this article has only scratched the surface of what SketchUp can do. There are many other tools available and even more ways to use the tools that I have introduced. I hope I have been able to dispel the myth that all computer-aided design software is complicated and has a steep learning curve. In future articles, I hope to share some more advanced techniques, which will help you make your drawing more efficient.   Learning to make your own personal component library, and using the “Paint Bucket” tool to give your drawings a more realistic look, will take your drawings to the “next level.” It’s easier than you think.

I truly hope this brief introduction to SketchUp has made you consider using it in your work. I promise it will save you time, impress your customers, and most importantly, make you even more successful in your career.

Additional resources:

Books:

Google SketchUp 7 for Dummies by Aidan Chopra:

An excellent book that I always keep nearby for reference. Whenever I go to look up a question I have, I find myself engrossed and come away learning something I hadn’t even planned on.

On the Web:

http://www.aidanchopra.com/ — The companion website to Google SketchUp 7 for Dummies. Includes video tutorials that follow the book, chapter by chapter.

http://sketchup.google.com/training/videos.html — Straight from the source. Includes great video tutorials for the beginner through advanced user.

http://www.go-2-school.com/ — The definitive website for SketchUp education. Offers training material for purchase, as well as a blog and free “webisodes” of their fantastic webcast, “The SketchUp Show.”

http://finewoodworking.taunton.com/blog/design-click-build — A blog from Fine Woodworking magazine dedicated to the use of SketchUp for the woodworker. Tends to cover more advanced techniques, and I am always amazed by their work.

http://garymkatz.com/ — A great website for the finish carpenter and where I was first introduced to SketchUp.  There are two SketchUp tutorials located on the Charts & Drawings page that I highly recommend.

http://www.youtube.com/user/toddmurdoc — My YouTube channel. A collection of short videos, covering some timesaving techniques for the carpenter who uses SketchUp.

Read this article in its original format (with more images) at TiC Issue 4!

AUTHOR BIO

Todd is a fourth-generation carpenter/woodworker who is currently employed as a corporate pilot. His schedule alternates between a week “on the road,” flying all over North America and the Caribbean, and a week at home in Northern Virginia.

While at home he enjoys spending time with his wife Jennifer and their three children.  The time at home also allows him to “escape” to his shop where he builds custom furniture and cabinets. Most of his work is for pleasure these days, doing only one or two paying jobs a year.

He began learning SketchUp as a way to kill time on layovers and quickly discovered he could use it to continue progress on projects back home. Having a detailed model completed ahead of time also makes his limited time in the shop more efficient, since all the details have already been worked out in a “virtual” prototype.

During college, while working for a local contractor, Todd vividly remembers shingling a roof one VERY hot summer day. He paused for a moment to watch a jet flying high over head and thought to himself, “Boy, I wish I were up there flying.” Ironically, he now finds himself occasionally looking out the cockpit window from 35,000 feet and thinking, “I wish I were down there making sawdust.”

I worked in finish carpentry and millwork for quite a while before I learned that you have to design things before you can build them: the less confidence I had about each step of a job, the more important it was to plan right to the end, before cutting one piece of wood.

(Note: Click any image to see a larger version. Hit "back" button to return to article.)

Some time later, I figured out that I didn’t have to design everything from scratch — lots of smarter carpenters had built most of the same stuff before. What I really had to do was look at their work! From that experience, I’ve learned that the correct way to build a house is to design the handrail first, then design the stair, and the rest of the house will follow.

I’m not at all self-taught. I went to school for woodworking, and I was lucky to have a superb teacher. And I was lucky to work for and with some really good, experienced, and generous carpenters on job sites, and woodworkers in mill shops.  In fact, A 75-year-old master named John Mesiti taught me woodturning, which got me into stair building.

But I couldn’t find a living stairbuilder to teach me everything I needed to know about the trade, so I had to learn from dead ones: craftsman who left their techniques behind in books; carpenters who left their work behind in old homes.

While learning to build stairs, one of the biggest problems I encountered was how to make a volute. What is a volute?

Pronounced Vol-ute, depending on where you hail from, the word originates from natural forms, like unfurling leaves, the shells of mollusks, or gastropods and ram's horns.

Come on! A volute is one of the most beautiful pieces of wood in a home. It’s the curved piece on the bottom of the stair; it’s the spiral, the beginning on the way up and end on the way down of every proper stair; a volute is the piece that supports the birdcage of balusters at the starter step.

The spiral volute design appears on fiddleheads both of the fern and the violin, and pairs of volutes decorate the capitals of the Ionic order. Volutes play a role in the old mystic golden number — the Fibonacci series, they have a kind of magic.

In fact, if the house is a body, and the handrail is the main artery, then the volute is the heart of a home.

And for carpenters, volutes provide a natural termination for linear molding and handrails.

For hundreds of years volutes have been a favorite way to start a stair rail, first because they are pleasing to the eye and, second, because they are comfortable to the hand. They lend a gentle slope to the start of every stair. Viewed from above, a volute spirals down into an eye, a focus, like the place where you drown in a whirlpool, where everything begins and ends — nothingness.

But I’m going off on a tangent, as usual, and Gary’s going to get upset with me. Back to carpentry.

Commercial volutes

Even commercial handrail systems — available from local lumberyards — include volutes. They are always the most expensive parts in the catalogue. High-end stair part companies offer handsome volutes and attractive stairs can be built with them. But for the most part, manufactured volutes have a few failings:

• They aren’t available in a wide range of species

• They aren’t available in a wide range of patterns.

• Available patterns are not for the most part historically correct.

Machine-made volutes are primarily designed for just that — to be made on automatic or semi-automatic machinery. The curves are kept open so that rotating cutters can reach into every curve, which means the rail never spirals in on a center — they have no eye…exactly, they have no vision, they fail to provide a natural and necessary visual termination and starting place for railing.

A commercial volute with an ‘upeasing’ (right) must be installed higher above the starting step than a volute with a wreath (left).

In addition, for ease of construction, commercial volutes curve in elevation, and then curve in plan — they have no compound curves,  which means they remain level until the second tread and must be set high on every stair. For that reason, commercial volutes require long balusters and tall newels; a person starting up such a stair must raise their hand uncomfortably high. (See Fig. 5)

Fig. 5

~~~

Why carve a volute?

When I started building stairs, all manufactured parts were made of beech, and all the old stairs I looked at were mahogany or walnut. I had to make rail. And I had to make complex curved parts. The volute seemed like the hardest part to make. But it doesn’t have to be — not if you start with a good drawing. In fact, a full-size drawing makes the best template, too.

If you want to build the best stair possible, if you want to be a real stair builder, you’re going to have to make your own rail parts (yes! You’ll have to learn wood-turning, too, so you can make your own balusters and newel posts — but that’s another story.) This article will show you how we make volutes in our shop. We didn’t invent anything here — the volute in this article could have been made by a Boston stair builder for a brownstone in Beacon hill in 1790, but we will show you a few modern tricks and techniques that make things go faster, particularly computer drafting, and power carving. If you have good carpentry skills, a shop space with basic woodworking tools, and an adventurous spirit, carving a volute might be a good place to jump your finish carpenter chops up to the next level.

The drawings

A volute is really made from two pieces: the scroll section, which is the portion of the volute that is level and spirals to an eye, and the wreath section.

A wreath is a stair building term for any compound curved piece of rail.

I draw the volute full size in both plan (from the top) and in elevation (from the side). Then I use these drawings to make full size patterns of both pieces. The patterns will go to the shop and be used to saw out the blanks and then carved. At the end of this story, Mike Kennedy will show you how that’s done.

Before you start

Here’s what you need to know before you start your drawing:

• What is the stair rise and run?

• What does the rail look like — it’s best to have section or piece of the rail.

• What’s the code on how wide and high the rail must be?

• How wide is the volute? And are you sure there’s enough room?

Think about the design, too. You don’t want a volute that ends at the center too big — like a dinner plate, or one that ends too small, like a cabinet knob.

Layout the volute

To draw the volute in plan view, I follow the same procedure every time. I draw the skirt board, second tread, baluster, and a short section of straight rail. Then I draw the volute. Next, I draw the bottom tread, because the stair is going to be better if the shape of the bottom tread follows the shape of the volute. Besides, I’ll need a pattern for the tread and riser too, and the drawing provides that pattern.

Start with the second riser

Here are a few tips that should help you better understand the process of drawing a volute by hand. Watch the video, read these tips, do both again, and then practice drawing a volute yourself.

The first step in drawing the volute is establishing the edge of the skirt board and the edge of the second riser. Where they come together I draw a baluster. The centerline of the handrail goes through the center of the baluster, and the inside and outside of the rail are drawn 1-3/8” parallel to the centerline, to give a rail which is 2-3/4” wide. Once these elements are drawn, I measure downhill 2 in. from the second riser to draw the first stop line, where the straight rail meets the curved volute. I’ve found that 0 to 4 in. will work on most stairs: I want to design the stair so that the curve of the bullnose on the bottom tread follows the curve of the volute; that way all the balusters will have the same relation to the bottom tread as they have to the straight part of the stair. In other words, the face of all the balusters will be plumb flush with the face of the skirt and with the riser of the bullnose tread. If 2 in. doesn’t work, it doesn’t mean you have to start all over. You can just redraw the location of the riser until the bullnose tread looks right!

I want to design the stair so that the curve of the bullnose on the bottom tread follows the curve of the volute...

The Shrinkback

A shrinkback is the amount that the spiral decreases every quarter turn of the volute. In this case, with a 11 in. volute and a 1 in. shrinkback, my first radius will be 6 in. (above), my second radius will be 5 in. (below), which adds up to the total width of the volute, 11 in.

For every quarter turn, I shrink 1 in. toward the interior of the volute, and each time I also draw a stop line at 90 degrees through the new center point --- which establishes the end of each quarter turn.

I make this same step for radiuses #1, #2, #3, and #4.

The forth radius center point is established automatically, it’s the intersection of the spring line and the stop line from the #3 radius. At this point, the centers have formed a 1-in. square. Radius 4 starts at stop line 3, and ends up back on the original start line.

For the fifth radius, the shrink back is 1/2 in. instead of 1 in., otherwise the spiral won’t close in on itself like a nautilus shell. A 1/2 in. shrink back makes the radius 2 1/2 in.

For the sixth radius, the shrink back is also 1/2 in. instead of 1 in. And that completes the spiral. The center of the last radius is the center of the 1-in. square; it’s the center of the eye of the volute; and it’s the center of the volute newel.

Layout the wreath

The wreath section is the upper section of the volute, which transitions from raked to level as it turns through the first 90 degrees. It has a compound curve because it curves in both plan and elevation. That compound curve makes it much more difficult to draw. In fact, it’s even difficult to visualize. Look at the animation below and you’ll see the drawing and the two patterns we’re about to create.

We have the plan view of the wreath from the volute drawing. In order to make a pattern for cutting the wreath from a block of wood, I first turn the scroll section drawing 90 degrees, so that I can see the elevation of the wreath. You’ll see me turn the drawing in the video, but the Sketchup drawings included with the text start with the stair turned horizontally.

Because the wreath turns and twists, curving in plan and elevation, I need two drawings, both of which are drawn in elevation and plan view. I know this is going to confuse a lot of readers. When I first learned how to draw a wreath, the only guide I had was a drawing in a fifty year old book. Learning from that drawing felt like breaking my own leg over and over again. It took me the better part of a week to figure it out the first time.

I’ve been trying to explain this process to my friend Gary Katz for ten years; now he wishes he’d paid better attention in geometry class! Most of you will get it much quicker!  I’m sure the video, this additional text, and the drawings (my thanks to Todd Murdock for the wonderful Sketchup illustrations!), will make it much easier to understand how to draw this complicated three-dimensional piece. Even Gary has drawn his own volute now, and we’re going to make him carve it next time he visits the shop!

The Elevations

Because the wreath curves in plan and elevation, and because we want to get it out of the smallest piece of expensive and rare mahogany as possible, we have to visualize the block of wood at an angle. That angle is the pitch of the stair!

Also, because the wreath curves in two planes --- it rises up the pitch of the stair and it turns 90 degrees with the spiral --- we need to make a pattern for both the top and the side of the wreath.

Drawing the patterns

I always start with an elevation view of the entire volute, which will give us the pattern for the side of the block. I use a common shop class technique of drawing the elevation dimensions under the plan view, which makes it easy to carry the dimensions from the plan view to the elevation view.

The first line. Start by drawing a line down from the center of the handrail right where the scroll section and the wreath section join (Line A, below).  I find that a 12-in or 13 in. line usually allows enough room to draw the whole elevation — the Side Pattern and the Top pattern; we’ll do the side pattern first.

The second line. Next, draw a horizontal line across the bottom of the drawing, like I said, about a foot below the plan view (bottom line, below, 13 in. below volute). That line helps establish the elevation of the handrail at the pitch of the stair. Think of that horizontal line as the run of the stair. Pretty soon, that line will become the centerline of the level scroll section.

The center of the handrail. The run of the stair, or the tread, is 10 in. I measure 10 in. from the intersection of line A and the ‘run’ line. From that point, I measure up the rise of the stair, which is 7 3/8 in. An elevation drawing is really like looking at the edge of the riser. That’s what we’re seeing now.

Next, I draw the centerline of the raked handrail by connecting the rise and run lines at the rake of the stair (center diagonal line, below).

After that, it’s easy to draw the top and bottom of the raked handrail. The rail is 2 1/4 in. tall, so I place a line 1 1/8 in. above and 1 1/8 in. below the center line.

The Top Joint. To start the top joint, I draw a vertical line from the plan view down to the elevation view, from the very top of the volute, where the straight rail meets the curved rail (see Line B, below). That line is really an extension of the Start Line, which is also the 11” line drawn for the initial spiral of the volute.

Next, I draw a line (K) square to the handrail so that it intersects line B at the centerline of the hand rail (see below). That’s the exact location where the wreath meets the straight rail, and that square line would make a butt joint. However, the joint would be clipped slightly on the outer curve, and besides, I like to have a little extra wood on the wreath for carving the curve to the straight rail, so I add another 2 in. or 3 in. to the block; that is line L which becomes the glue line and the end of the block.

The Bottom Joint. Now we need to draw the joint where the bottom of the wreath meets the level handrail of the volute. To describe that joint, I have to establish both the height and the width of the handrail. I start by using the first horizontal line I drew, at the bottom of the drawing — that is the centerline of the level scroll section (below).

Next, draw a line 1 1/8 above and below that centerline, establishing the side of the handrail in elevation (below).

I layout the width of the handrail the same way, using line A, the first vertical line I drew, which was carried down from the volute — the center of the handrail where the scroll section meets the wreath section. Because the handrail is 2 3/4 in. wide, I draw a line 1 3/8 in. on each side of  A. Those lines are F & G.  (The top and bottom lines of the wreath are darkened for clarity)

Now I can trace a small piece of the handrail, in elevation, right on to the drawing, in the rectangle formed between F & G and the top and bottom of the horizontal rail.  Believe it or not, that endgrain section is the face of the buttjoint at the bottom of the wreath!

The side pattern. We’ve finished the elevation, now we can use it to make a paper pattern for the side of the block. We need a piece of wood thicker than the height of the 2 1/4 in. rail, so I use a piece of 12/4 or 2 3/4 in. thick stock.

To establish the top and bottom of the 2 3/4 in. block of wood on the elevation, draw a line 1 3/8 in. above and below the centerline of the raked rail (Lines D & E). To locate the lower end of the block, draw a line (J) square to D & E, so that it just misses the bottom corner of the handrail near the bottom of line F. Because the top of the block is already defined by line L (see Side-Top Views), we now have the side pattern complete (below).

The top pattern. Before starting the Top Pattern, extend lines G & B to line D (below).  By looking at the plan view of the volute above, we can tell that the wreath section is 6 in. wide. The block is already at the pitch of the stair, so it’s easy to draw the top view at the same pitch, right above the side view.

I start by measuring 6 in. up from Line D, and strike Line H, parallel to line D (below). That establishes the width of the block and the top pattern. Extending lines J & L to line H completes the rectangle of the Top Pattern.

Next, draw a line 2 3/4 in. from and parallel to line H — that represents the inner edge of the straight rail (M, below).

Layout the Ellipses. Where line B intersects line D is the center point of both ellipses (P-1, below). Draw a line (B-1) square across the top of the pattern, parallel to line L-1. Line B-1 defines the ends of both the inner and the outer edge of the ellipse.

Don’t forget we added a couple inches to the wreath to make it easier for Mike to blend the wreath and the straight rail. So from line B-1 to line L-1, the wreath is carved straight.

The intersection of line F and line D (P-2) is the starting point of the outer ellipse.

The intersection of line G and line D (P-3) is the starting point of the inner ellipse.

The intersection of line H and line B-1 is P-4.

The intersection of line M and line B-1 is P-5.

Draw the ellipses.

I use a trammel with two points and a pencil, and a small square, to draw the ellipses for the inside and outside of the rail. You’ll have to watch the video to see how it’s done, but here’s how to set the trammels — just remember, always set one of the trammel points on P-1!

For the outside ellipse, put the pencil on P-4, then set the inner trammel point on P-1. Next, move the pencil to P-2, then set the outer trammel point on P-1. Swing the ellipse with the points held against the square the way I do it in the video.

For the inside ellipse set the pencil on P-5, then set the inner trammel point on P-1. Next, move the pencil to P-3 and set the outer trammel point on P-1. Again, swing the ellipse with the points held against the square the way I do it in the video.

Once the drawing and patterns are completed, I hand them off to Mike Kennedy. From that point on, the woodwork is in Mike’s hands. Watch the video to see how Mike uses the paper patterns to cut the wreath out on the bandsaw.

And don’t miss Mike’s article on carving the volute. If you were lost at any point during this article, don’t feel bad. I’m confident that if you watch the videos, read the text, look at the pictures, and draw it yourself, you’ll understand the process and be a better carpenter for it.

If you use CAD software for drawing your work, here’s a short video that should help.

If you read this story, then draw and carve a volute…please take pictures and send them in to the magazine! Share your work so we’ll all learn more about our craft.

Well guess what? There is a language to classical design, too; a vocabulary that’s dependent on moldings for communicating purpose in a room. If you speak the language, all your finish work—your, bookcases, mantelpieces, doorways, and ceilings―will communicate fluently with your customers.

(Note: Click any image to see a larger version. Hit "back" button to return to article.)

If you don’t speak the language, your work will look funny and awkward. Put simply: You might be using the right words, but if you put them in the wrong order or upside down, they won’t make sense.

Supporting Moldings

Centuries ago, the Greeks and Romans worked out a set of rules for moldings. Each profile had its place and purpose. Some shapes were designed merely to embellish an architectural detail, while others served to separate architectural details. The two profiles that are most often confused and most often used incorrectly by today’s builders are terminating profiles that finish an architectural detail, and supporting profiles that hold or carry a weight above.

In the forward to Theory of Mouldings (C. Howlard Walker, reprinted 2007), Richard Sammons provides a great definition and an easy way of determining whether a molding is terminating or supporting. Sammons says that if the final line of the molding curve is pointing out, it is a terminating molding; if the final line of the curve is pointing up, it is a supporting molding. Or put another way, terminating moldings have a concave curve at the top, and supporting moldings have a convex curve at the top.

Let’s take a look at supporting moldings first. Supporting moldings have more meat or muscle on the bone near the top. They don’t look delicate! They look like a clinched fist on the end of your forearm. A perfect example of a supporting molding is a corbel, the embodiment of strength in architecture.

Some supporting moldings play a more subtle role. While the corbel forms the main support for the mantelpiece, look closely and notice the molding beneath the mantelpiece. You may be quick to label this profile as crown molding, but it’s actually bed molding. The top of the bed molding profile points up not out, so it adds another layer of visual support to the mantle above.

Band molding or panel moldings, in all their various shapes and sizes (from egg-and-dart molding to lamb’s tongue, to ogee chair rail and dado moldings), are another example of supporting moldings. The top curves on band and panel moldings are convex, putting muscle where it’s needed most – at the top of the profile.

Terminating Moldings

Terminating moldings are exactly the opposite, they’re much more delicate on the upper top edge, a clear sign that they’re not meant to support any weight from above. Though they might seem purely decorative, terminating moldings actually served an important purpose on classical structures. Like the brim of a hat, they helped deflect rain away from the wall below. Today, the most common pre-formed rain gutter actually uses a modified shape of crown molding, the most common of the terminating moldings.

The top of crown molding curves out, finishing the top of – or “crowning” – any architectural detail it’s attached to, from the mantle piece to the rake of the beautiful open pediment. Most crown moldings used today are called cyma moldings because they combine both concave and convex curves to form their profiles. Cyma recta is the classic crown shape with the top concave curve pointing out. On the other hand Cyma reversa, with the convex curve on top pointing up is the proper profile to use as a supporting molding, beneath a mantelpiece or a shelf.

One area that gets really confusing is crown molding at the corner of the wall and ceiling. Should crown molding at the ceiling be a supporting molding or a terminating molding? Actually, the wall in a home is meant to resemble a classical column – so the uppermost crown should be a terminating molding. But sometimes it’s not. I’ve frequently installed a supporting molding at the ceiling when I’ve used a one-piece crown, but most often when there’s a secondary soffit or light well above, which must
also be trimmed with crown.

Terminating moldings help produce dramatic effect at the top or termination of everything we build. As Marianne Cusato and Ben Pentreath put it in their book Get Your House Right, (also co-written by Richard Sammons): “The emphasis of a terminating molding, or cyma is outward.” That outward projection works as a lip or an outline to finish off any architectural detail.

Cyma Recta

No discussion of supporting and terminating moldings would be complete without a look at the two primal shapes that form the foundation for most moldings.

Cyma Reversa

These two opposing profiles follow the same classical rule: if the upper line of the molding points out, it’s a terminating profile. If the upper line of the molding points up, it’s a supporting profile. Supporting profiles always have more mass at the top. Terminating profiles always have less material at the top.

Cove molding is another profile that can be used as terminating molding. The delicate lip at the top of a cove’s concave curve works well to finish off less ornate architectural details. Many terminating crown patterns incorporate a deep cove to emphasize the projection of the terminating molding.

Finishing Up

Too often supporting and terminating moldings are installed backwards, upside down, or they are swapped in position and make no architectural sense. Too often a terminating molding is placed underneath something it can’t carry visually. For example, the ubiquitous 8010 crown should be used to finish off a detail, and too often we see it installed underneath something heavy, leaving us to wonder what it is about that detail that we don’t like or that doesn’t feel quite right.

The area in architecture where I see these moldings most often mis-used is mantles and shelves. It is very common to see a terminating molding get capped by a large block or thick piece of wood, which happens frequently with mantel shelves.

Wrong

I see this type of composition all the time! Now that you know better, it’s easy to see that the thin top of that crown molding isn’t strong enough to carry the weight of that heavy shelf. A supporting molding would have made much more sense.

Right

This is how a classical cornice should be constructed, with a cyma reversa supporting molding beneath the soffit and a cyma recta terminating at the top!

Never ask a terminating molding to visually carry something so large and heavy. And by the same token don’t finish off the top of a detail like a door header or mantle with a supporting molding that visually begs to carry something heavy above it.

Remember, a simple twist or rearrangement of words, and suddenly your sentences make sense—or they don’t! The proper use of terminating and supporting moldings can make your bookcases, mantels, cornices, and crown feel right and make visual sense. Understanding and applying these ancient rules will improve the value of your craftsmanship, and increase the value of your work in the eyes of your clients, too.

Read this article in its original format (with more images) at TiC Issue 1!