The trim that surrounds a door frame is called casing, and it’s always installed before baseboard and chair rail because they have to butt against it. Casing is also the easiest type of molding to install because the joinery is simple, making it a perfect first project.
I’ll start off by explaining the details of casing joinery and describing how to measure for new casing around a door frame. I also talk about making a cut list, so when you cut your casing it will be perfect the first time.
Chapter 2: Part 1
A serial publication of excerpts from Trim Made Simple by Gary Katz
Training techniques for apprentice carpenters and serious DIYers
Most trim carpentry revolves around using a miter saw. In this article, I’ll introduce fundamental techniques for cutting correct miters in casing—techniques that I’ll build on in later articles for baseboard, chair rail, and crown molding. I’ll demonstrate a simple system for cutting casing that will help you cut each piece of molding to exactly the right length—every time. In future articles, we’ll use elements of the same system for cutting other types of trim.
Before installing new casing, the old molding must be removed, without damaging the wall or the jamb. I’ll cover the best and simplest tools and techniques for that job, too. Then I’ll demonstrate two ways for installing moldings: the time honored one-piece-at-a-time method, and a new way of pre-assembling casing that ensures tight miters and a neat job. By the end of part 2 of this story, you’ll be able to install new casing with confidence.
Installing casing is not only the easiest trim carpentry chore but requires the least amount of tools. Buy good quality tools. Good tools work better and last longer.
|Three 7-ft. pieces of 2 1/2-in.-wide casing in a “3-step” profile pattern, made from fingerjointed, unprimed wood|
|Carpenter’s glue for tight, long lasting joinery|
|Nails (nail gun) for fastening the molding to the jamb and wall|
Understanding Casing Joinery
Before tackling any new job, make sure you see the whole picture. Casing can be confusing. A quick drawing is often the best solution, especially when it comes to miters. Miters are angled cuts, so they always have a short point, where the length of the material is shortest, and a long point, where the length of the material is longest.
Some carpenters refer to the short point as the “heel” of a miter, and the long point as the “toe,” which is another way of understanding the angle of a miter. Because casing surrounds the outside of a door frame, the short points matter most: The short points of the miters are always on the jamb, on the inside edge of the casing, near the door. For casing, all measurements are taken to the short points.
Avoid frustration. Always make cut lists for moldings. That’s the best way to ensure a smooth enjoyable job. With cut list in hand, you can confidently head for your saw; without one, you will likely find yourself in front of the saw trying to remember a crucial measurement, and then heading back to measure again. And with a cut list, you’ll always know which way to miter your moldings—without closing your eyes and trying to remember the room you just left.
Make a Cut List
|1. Measure the head first. If the old casing isn’t on the jamb, measure the inside of the jamb (inside dimension, or I.D.) and then add 1/2 in. for 1/4-in. reveals on both sides of the jamb.|
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Please don’t try anything you see in THISisCarpentry, or anywhere else for that matter, unless you’re completely certain that you can do it safely.
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At first, cutting miters in casing is confusing. To make the job easier, always place casing with the back edge against the miter saw fence. That way, the long points of the miters will always be against the fence, and the short points of the miters—and all the measurement marks—will always be nearest to you, where you can best see them. With the measurement marks away from the fence, it’s easy to guide the saw blade right to the mark, which you’ll see when you cut the casing legs.
Cutting the legs
|1. Cut the legs first. Place one piece of casing on the left side of the saw. That will be the left-hand leg. Place another piece of casing on the right side of the saw, that will be the right-hand leg.|
|2. Measure up from the bottom. Hook your tape measure on the bottom of the casing, stretch the tape up towards the saw, and make a measurement mark on the font edge of the casing. Do the same for the opposite leg.|
4. Look from front of saw. Sighting down the saw blade is the hardest way to align the blade with the measurement mark. The measurement mark is easier to see from the front of the saw, even with the blade spinning. With your thumb wrapped around the casing, slide the casing toward the blade, creeping the measurement mark forward until the blade cuts right on the mark.
Always cut the head casings last because you can cut them from shorter pieces (sometimes from legs that you mistakenly cut too short!). The head casing is a little trickier to cut because both sides have miters. A simple technique makes it very easy to cut double miters at exactly the right length.
|1. Miter right end. Clamp the casing to the end to the miter saw extension table, with the short point flush with the edge. Hook your tape measure on the edge of the miter saw table, then pull the measurement.|
|2. Measure with a sharp pencil. Use a no. 2 1/2 lead pencil for a sharp, fine line. Never round off fractions. Always make measurements exactly, to within 1/32 in., which is a little more or a little less than the nearest 1/16 in. mark on the tape measure.|
|3. Make a practice cut. Hold the casing with either your right or left hand placed at the end of the miter saw fence. Wrap your thumb over the front edge of the casing. Make a practice cut about 1/2 in. away from the measurement mark.|
|4. Creep up on measurement mark. The more you use a miter saw, the closer you’ll make your practice cuts and the fewer practice cuts you’ll make. But don’t rush the learning process. Cutting right on the measurement mark is what matters most.|
Cut Casing with a Miter Box
Hand-powered miter boxes work well for cutting small moldings, as long as you use a good one. But no matter what type of saw you use, a miter saw stand and continuous support for your material is essential.
|1. Clamp your workpiece. When using a miter box, be sure to clamp the material securely to the table and to the tool. That’s the only way to ensure a perfect miter.|
2. Let the saw do the cutting. Too much pressure on the saw will distort the miter cut. Never “try” to make a miter saw cut. Allow the saw to cut by itself. Pull the blade smoothly and gently backwards across the molding. Use light pressure to push the saw forward. Move your arm slowly back and forward as if it were a machine.
Keep an eye out for Part 2 of “Casing Doors,” coming soon from THISisCarpentry!