I’m a GC with a trade background of framing. Here in Southern Oregon, often times the framing crew is also the building wrap, trim, siding, and window/door installation crew. This includes fascia. At least that’s the way the guys that taught me did it. Luckily, I had some good mentors. However, installing prow fascia isn’t an everyday task. In fact, it isn’t even a task that I see more than once every few years.
When Gary Katz asked me to build a new shop for him I figured I was up for the task. The plans showed it was really just a big rectangular barn with a simple gable roof and a 4/12 pitch. The rendering showed a prow feature on the upper overhang at each end of the building, but the elevation showed a standard two-foot overhang. I could’ve worried about the discrepancy at the time, but I had a lot of work to do and wasn’t going to be dealing with that feature for months. After all, we hadn’t even broken ground yet, and I had many more pressing concerns.
Two months later, with the trusses installed, it was time to construct the overhangs and sheet this box. And it was time to get to the bottom of this prow design. After posing the question to Gary, he said, “I’ll tell you what: let’s make it easy. Just start the prow at your last outlooker and extend the ridge out an extra foot. Oh, and by the way, you’ll be installing non-structural WindsorONE fascia, so you’ll need to install sub-fascia as well. I want the raw sub-fascia surfaces of these overhangs double-primed—even the surfaces that will be covered. And, I want an air gap between the sub-fascia and the fascia.” …So much for easy. And it got a lot harder, too! With some clients, you have to just bite your tongue.
Like any project, I wanted to get these prows built correctly and completed in a timely fashion. However, this project had an extra element of pressure because of the client. Even when I don’t think he’s around, I can feel the guy watching over my shoulder the whole time. And, he’s got lots of cameras.
The first thing I did was create a full-scale plywood template of the roof surface of the prow.
|This allowed me to measure the required angles for the transitional lookouts, ridge, and sub-fascia miters.|
I had already set the transition lookouts and taken my common rafter measurement of the distance between the transition lookouts and the center of the ridge on the south gable end of the building.
Since Gary told me to extend the ridge out an extra 12 inches, I simply plotted this on my plywood template.
|I drew in the outlooker where the sub-fascia was going to make the transition from parallel to prow, and I measured the angle with my speed square…|
|…I repeated the process at the ridge where the sub-fascia would peak and turn down the rake, maintaining its prow profile.|
I used a T-square to make it easy to plot all of these points and intersect lines on the template. I was able to measure the prow length for the sub-fascia, and then derive most of the required angles.
The plumb cuts on the regular gable fascia were easy to determine—they were simply 18.5 degrees, with the 4/12 pitch of the main roof. The prow plumb cuts were a little more difficult to figure out. I am no mathematician or engineer, but since the overhang ridge is horizontal and the regular fascia is perpendicular to it, this situation is just a sequence of right triangles, and similar to a hip/valley rafter (irregular in this case). I used a regular calculator and the Pythagorean Theorem (a2 + b2 = c2) to calculate the unknown dimension of the triangle. I then plotted it out, and measured the angle for the prow plumb cuts. I also checked my math with a construction calculator, just for reassurance.
I knew the pitch of the regular roof (4/12) but I had to figure out the pitch of the prow, so I needed to find the horizontal run of the prow fascia to complete the equation.
My original plywood template of the roof surface gave me the “prow length” (39 13/16 in.), which was the diagonal or hypotenuse of the triangle, and I also knew the vertical “rise.” This allowed me to determine the prow “run” using the Pythagorean Theorem. The prow length was the “c” in the equation and “a” was the rise. I knew the rise was 12 in. because the common run of the prow was 36 in. Since the pitch of the main roof was 4/12 (4 in. of rise for every 12 in. of run), and 3 x 4 in. = 12 in. So: 12 in.2 + b2 = 39.8 in.2.
Back at the template I laid out the 3 points on a square corner of the plywood and used my speed square to determine the pitch angle of the prow sub-fascia: about 17 degrees.
|This is how to use a construction calculator for the calculations. It’s quick, precise, and allows you to keep all your measurements as fractions.|
The regular gable sub-fascia is pitched at 18.5 degrees, and the prow is a 17.5 degree pitch. Pretty close. The very small difference in pitch makes the length of the mitered plumb cuts very close to one another.
Of course, everything lays out perfectly when you’re drawing on a piece of plywood and using a calculator while standing on the ground. But we all know that’s not the real world—it never works that way when you’re up twenty feet in the air with a circular saw. I took into account that some angles and cuts of the actual sub-fascia and fascia would need to be modified—after all, even the trusses and lookout framing isn’t perfect. I made sure to leave all of the sub-fascia pieces a little long so I could afford to recut something if I had to.
On the Ground
The first order of business was to fabricate the ridge lookout while I was still on the ground.
|I took two 2x4s and ripped one edge on each piece at an 18.5-degree bevel (the common plumb cut angle). I then preassembled a “mock up” of the ridge lookout, making sure it would accommodate the planned decorative bracket beneath it.|
Satisfied with the mock up, I cut the prow tip on each half of the ridge lookout on the miter saw by placing the bevel cut against the fence to simulate their finished position on the roof.
|I set the bevel angle at 0 degrees (to simulate plumb), the miter angle at 18.5 degrees (the prow angle measured from the plan view), and cut the first half of the ridge.|
Then I swung the saw to the opposite 18.5-degree miter angle to cut the other half of the ridge. Cutting the ridge pieces “in position” on the miter saw was a critical step, because it provided the slight bevel angle (just under 6 degrees) that the lookouts needed in order to keep the prow fascia plumb.
In the Air
I knew I’d be on those gable ends for a while, so I built a working platform for each one. I needed the platforms to build the overhangs and to help make the painting easier, too.
Installing all of the outlookers was easy because I had asked the truss manufacturer to build dropped top chord trusses for the two gable ends. I asked him to drop the top chord an inch and a half (the thickness of my outlooker lumber). This way I didn’t have to cut notches in the top chords of the trusses for all of the outlookers.
When I install outlookers, I always attempt to install them perpendicular to the gable end truss using my framing square. For these prow overhangs, I went the extra mile and used a framing square knowing that every little thing that I could do to make the overhang framing as perfect as possible would pay off when I started cutting the transition outlookers and installing the sub-fascia.
|I paid extra attention to the ridge outlooker, too, making it both square to the gable end and level using a temporary brace.|
Next, I cut the transition outlookers to match my plywood template. I wanted the gable fascia to transition into the prow fascia in the middle of the outlooker so that the outlooker could support both pieces of sub-fascia.
|I finished the cuts in the transitional outlookers with a Japanese saw.|
|I braced the outlooker for the ridge with a temporary 2×4, knowing that eventually we’d be replacing that brace with a custom site-built bracket.|
With the sub-fascia on the eave overhangs cut to length, it was now time to cut and install the sub-fascia on the gable end. I precut the transition angles on the four pieces of sub-fascia on the ground using the plumb cuts and miter angles I had figured out earlier—leaving all the pieces long and hoping for the best. I started on the right side with the first piece of normal raked sub-fascia. Letting the extra length of the board run past the eave, I slid the sub-fascia into position on the transition outlooker and screwed it at both locations.
|I held the prow piece in position to check the intersection at the transition outlooker. Of course, a little adjustment was necessary—like I said, math on the ground doesn’t always equal what’s happening 20 ft. in the air.|
While adjusting the fit of the sub-fascia at the transition outlooker, I was careful to keep the prow piece in plane at the ridge. If it didn’t plane in correctly, the miter and bevel at the transition would open.
Installing the Fascia
We used WindsorONE 2×8 fascia. I was glad that I did my homework when I installed the sub-fascia because it made installing the fascia a breeze. I wanted to work my way up and down the fascia in the same order as the sub-fascia. I cut some fascia scrap into 18-in. long mock-up blocks and used the same miter and bevel angles as I had used on the sub-fascia. This helped me pinpoint the intersections of the fascia. I held the mock-up blocks against the sub-fascia to check the joinery and make any final adjustments to the angle cuts. I temporarily installed each piece of fascia until I had all three fascia intersections fitting perfectly. Then, I removed the fascia and stapled on strips of home slicker that I had precut to 5 inches wide.
The home slicker provides a quarter-inch gap between the sub-fascia and the fascia, which allows any moisture—either from the moisture content of the wood or from the air—to drain and dry out.
Finally, I nailed on the fascia permanently for the last time, cut the tails at the eaves, and told the painter not to screw it up.
|I started final assembly at the prow.|
|Then I worked my way down to the transitions.|
|And I finished at the eaves.|
In the end, these were fairly simple prows to frame in comparison to others. The sub-fascia was the key to this project. I knew if I dialed in the sub-fascia, the fascia would be much simpler. And it was. I used KD fir 2×6 for the sub-fascia. I made mistakes with that material instead of the WindsorONE. I’m not going to lie to you: about half of the prow sub-fascia pieces worked on the first try, and the other half had to be “adjusted” using the old hunt-and-peck system, which a few times required several cuts up on the working platform using a circular saw. That is why I left the pieces long to start with.
Writing this article forced me to really think about the best, fastest, and most accurate ways to tackle installing prow fascia, and it seems like there are a lot of potential pitfalls. For starters, there must be hundreds of different potential prow angles and pitches. Each prow gable could present a whole new set of calculations. I consider myself to be a bit of a perfectionist, but in my experience, it’s very rare to frame a 20-foot tall structure and have the rooftop components perfectly level, square, or straight, which is what you need to calculate and pre-cut prow fascia. Math and geometry on paper (or plywood) are basically perfect. But in the real world, even the slightest error in a prow fascia cut or angle, a crowned gable end rafter, or a slightly cupped fascia board can leave your miters and bevels open. And to make matters more difficult, most of us are cutting fascia with pencil lines marked with a framing pencil and a speed square, and we’re making a compound miter cut with a circular saw. Prow fascia should be cut using a miter saw.
The Whole Story
Some of you with sharp eyes may have noticed that some of the photos showed a slightly different approach. Here’s why:
After the sub-fascia was completed on the south gable of the shop, I set up my platform on the north side of the shop. Like I said before, the first time you do something it always takes longer, but the second time is always easier and faster. I was pretty excited to take what I’d learned from the south side of the shop and put it to work on the north side.
That’s when Gary walks up and says: “Hey, Scott, I’ve got an idea…”
By that point, I’d been working with Gary for over six months and I’d learned to fear that phrase, with good reason. He said, in the kindest voice, and as if it wouldn’t be any problem:
“Could you frame the prow on this end a little different? I want you to frame this end so the fascia transition to prow breaks square instead of plumb. So the peak of the prow tips out away from the building. And you’re taking good notes, right? I’m going to need you to write an article about both of these methods.”
Right! On both counts. Just when I’ve got it figured out, the “client” throws me a curve ball. After careful consideration (was it time to walk off the job?), I realized that I really didn’t know how to calculate the miters and bevels at all—there was nothing to go by.
I started by cutting the ridge outlooker ends without a bevel, which forced the fascia to tip out of plumb about 6 degrees. I knew the transition outlooker wouldn’t need a bevel either—it was just a simple inside corner miter—and I could precut those ends of the sub-fascia. However, pre-determining the miter and bevel angles at the ridge was a total mystery.
|I started with the same angles I used on the other prow, but they were off substantially. Let’s just say it was a good thing that KD 2×6 is inexpensive! I essentially had to hunt-and-peck my way through the peak of the prow.|
Installing the actual fascia was much easier because I had taken my lumps on the sub-fascia and I used the same method of mock-up blocks that I used on the south end of the shop.
After I finished with the prow gables, I reviewed my notes on the finished bevels and miters. I had a hard time detecting a relationship between the two methods. And I still don’t know how to figure out the miters and bevels of intersecting tipped-prow fascia. I am sure that there are carpenters out there with more experience in this than me (Sim, are you there?). I also can’t think of many other parallels to this aspect of framing except for angled and raked balloon-framed walls, which present a similar problem. Of course, being proficient with SketchUp would help determine these miters and bevels. But I didn’t speak with Todd Murdock until after this job was done!
For me, the tipped prow facia was so much more difficult to calculate and construct than the plumb prow facia. And the real rub is that I don’t think anyone is ever going to notice the difference. That’s a lot of extra time and effort for essentially the same result.
Of course, if the roof pitch were steeper, or if my prow extension were longer, the two ends could look totally different. I guess the real lesson to be learned is this: Wait until Gary is out of town for a week and then build both ends plumb!
Safety First… HAHAHA. I know that this happens on the job site but why post the pictures of something so seriously dangerous for the world to see?
Precisely for that reason–because it happens on the jobsite all the time–many of us work that way. Yeah, maybe one day we’ll look back at photos like that and say: “Wow, look at the silly things guys did back then,” just as we look at Bernice Abbott photographs of skyscrapers being built and steelworkers sitting on a beam during lunch. I’ve shot photos of much worse–two guys standing on a pallet on a pettibone at it’s furthest extension framing a 16/12 roof over an oriel tower. I’ve been on scaffolding that was a lot more dangerous than the 4×8 platform Scott built to work on those gable ends.
Old buildings with a dormer like that usually had windows in it. Great way to get light and ventilation. I think it would look better with them too.
I thought about installing clerestory windows between the two roofs, but decided against it for two reasons. First, I needed to have rigid control of daylight inside the shop and studio–I didn’t want to deal with extraneous shafts of light coming into the shop or studio and having to flag or scrim that light when I’m shooting photos/video; or daylight constantly changing the ambient light in the room. And second, I didn’t want the heat loss.
Great job Scott! Well written and detailed. Gary’s challenge us and make us more able. It’s a theme with him. Thanks Gary!
that is a great article. I too in hindsight would have waited till the customer was out of town! Other than setting up the mitre how critical is it for the subfacia to be as tight as you had yours? No one around here seems to worry about it.
Thank you. I agree that a lot of people (carpenters, contractors, customers) don’t worry how tight your sub-facia is. I guess the level of “perfection” is situational. I am kind of picky about my work in general (sometimes to a fault), and in this case with Gary snapping pictures of my work left and right and knowing that these pictures are going to end up being seen by lots of other carpenters,…………I wanted it to be tight.
Scott good detailed article. Love the full scale geometric drawing for the angles. This prow gable end would be referred to as a Crow’s Peak. Hope the job was time & material. Waiting for Gary to take pictures of you working must have added months to the project.
Thanks, Sim. All of the illustrations in the article were created by Todd Murdock. I think without his contribution, this would be a much more difficult topic to explain. We did slow down for photos, occasionally, and it was hard to get used to at first. But looking back, it was a lot of fun. Did you refer to tipped prow facia as a “Crow’s Peak?”
Der verkantete schräger Giebelsparren
The canted oblique gable rafters
Crow’s Peak Gable Rafter
Crow’s Peak Prow Rafter
Whatever you call the prow gable rafter rotated perpendicular to the roof surface it can be challenging, to find the correct miter angle and saw blade bevel angles for the ridge cut.
Here’s a link to the math on the prow rafter ridge cut.
my house has prow ends. the fascia is tilted 8° and the outside corners are square. when I added 6″ of rigid insulation to the roof I had to build up all the facsia, a lot of fancy cuts. driving around town I now notice this detail and it looks far nicer than the plumb-cut fascias.
Very cool!Great details!We would call that a Boston Ridge around here
Thanks, Tom. You must be from the Northeast?
Nice work. I appreciate your commitment to quality work.
Great state of N.J.Scott..thanks for the reply!
I love the Demo you posted to view the angle cuts and fascia on the Gable. May I ask what program are you using. I really do like your prospected way of teaching carpenters to use technology to view their work before taking on that task.
The CAD tutorial, as well as all of the drawings in the article, was provided by Todd Murdock. He was using a version of a program called Sketchup that you can download online for free. It is a great resource. In my opionion, this article would not be very effective with out his contribution.
One of the better Sketch-Up lessons I’ve seen. Nice job.
Your sketch up tutorial was excellent. I have yet to learn this program well, but your step-by-step lesson gave me more confidence to keep at it. You’ve illustrated just how valuable it is as a tool for field carpenters–and not just designers.
I was also thinking about the subtle difference you present between the “plumb” and “tipped” prow–and why one might choose one approach over the other. Please correct me if I am wrong, but it seems the difference would have be more apparent (and warranted) had the fascia included a rake moulding with radiused profile(s) of some sort which would not have mated up in a plumb cut. In that case it would seem the decision to “tip” the prow would have made things easier and cleaner because you are simply bisecting the offset angle in the same plane (I think). Another way of looking at this hypothetical trim dilemma would be to visualize the top roof line as a ceiling line around which you were choosing to run a crown moulding profile.
Otherwise the decision to “tip” with no mouldings merely (IMO) serves to dramatize the projection (by 6 degrees) of the prow (and perhaps make you scratch your head further)…which could also have been achieved “in the plumb” by simply increasing the dimension of the overhang.
Where can I buy a carrier tools with shoulder straps as yours ?
Those bags and suspenders have been retired. They had exceeded their life expectancy by at least three years due to all of the extra rivets and zip ties I added as needed. They’ve been replaced with a nice Occidental Leather setup that I bought at my local tool store. I don’t know where you live, but I think you could find a nice set of bags with suspenders at most lumber yards, tool stores, or (I hate to say it) the big box. And if that doesn’t work – jump online.
I was thinking further about the tipped prow…and looking at your photos more closely. My thought about bisecting on the same plane in order to accommodate potential rake mouldings is predicated on the fact that the lower gable end rake would be tipped at 6 degrees as well. It does not appear to be. So it got me asking one more big question… and two smaller questions:
1. Why DID Gary have you “tip” the prow on the entry gable to begin with?*
a. Did you have to cut one gable end offset rake board slightly wider than the other to accommodate the “plumb” projection side?
b. Did you have to bevel the top of the “tipped” rake section to plane out with roof sheathing (theoretically)? More “tip’ might warrant this to be the case, correct? So that would mean having to calculate the width of stock needed to plane out the roof and mate up with the exposed lower fascia edge.
* It seems to be a legitimate and intuitive design request (effect, balance, harmony) over the “plumb” option… rather than a request to make your life more difficult and complex on the jobsite :0
1. I don’t think Gary was trying to make my life miserable. I think he was challenging me to write an article about both styles. And, in this case, since the two styles had very little visual differences, his shop design/harmony was not affected.
1a. No. The tip angle was so slight that there’s next to no noticeable discrepancy in the height of the facia from an elevation view. If the tip angle were more pronounced, I am certain that we would have had to consider using a wider stock for our facia in order to appear balanced with the lower rakes.
1b. Good catch. Yes….technically. Beveling the top of the tipped facia could be required in order to allow the roof sheathing to lay flat on top of the facia. I did not do that on Gary’s shop because the tip I was working with was so slight that my sheathing and roof finished had no problems covering the small gap/void created by not beveling. But, looking back, I wish that I would have for the article.
Thanks for your comments,
I always find it is helpful to look at prow roofs as one half of a valley, Which in this case, mathematically would be an unequal pitched 4/12-12/12 valley. The Prow side being the 4/12 side of the valley rafter. The “tip” that could be introduced is equal to the backing angle of a the 4/12 side of said Valley. 5.739º.
The plumb version of the prow is the one that would actually need the bevel (think trough) on the top of the fascia as it is essentially one half of a valley. In this method the Fascia Bevel angle is equal to the Footprint Angle ATAN(4/12) or 18.435º/71.565º. The Miter angle is equal to the Hip angle 17.548º/72.452º Two angles which are easily accessible.
The tipped version would plane out to the roof because the “tip” is equal to the backing angle. This option may seem tempting at first because you don’t need to know the backing angle and the lower miter angle is a simple 90º cut…but it introduces some pretty complex math in order to find the other Fascia and Miter angles.
Around here we call that detail a “thunderbird” if it’s a pointed extension or a “outrigger” if it’s a square extension. I believe that both served the same original purpose to cover the beam that held the pulley for hayloft access. Hence, the end with the beam and window below looks ‘right’ while the end without a window looks ‘a bit off’. Now you just need a pulley up there.
I would suggest to others not to frame it as pictured; Rather, order your gable truss a full 3.5″ shorter than the rest of the trusses so that your lookouts can be framed on edge for a sag-free future. Also, and especially for a shallow 12″ extension, I may have framed the entire rake conventionally (lookouts on edge as mentioned) then added the prow extension separately. For a prow extensions exceeding 12″ I have left my outriggers long then framed through [squarely] with blocking. Then come back through and cut the angles to add the extended subfacia.
It appears that the top bracket is substituting (architecturally) for the notion of a beam outrigger on what I call a “work house” style building. I like it. I also think the brackets Gary has designed are plenty strong to carry the light (and relatively modest) overhang and fly rafter load (particularly coupled with the short axis 2x cantilever support). I also like the window/loft detail (even if it’s turns out to be faux) that reinforces the notion. However, what kinda works against the whole faux “prow” lift point drama is the covered entry projection right below it (ooch!). It’s one of those architectural ‘faux pas’ where something intuitively seems out of place…but you can’t quite put your finger on it. That is until you think about why the prow detail is (or should be) there in the first place. You may not have picked up on it because it’s not shown in the side-by-side photo comparison, but rather in the sketch up rendering.
I give you alot of credit for working on Gary’s place..I don’t think i coulda done it..without throwing up once a day that is
Hi, don’t know for sure but is not an outside corner with cedar lap siding the same math?? Awesome work, there should be more schools for the trades in our country. Think of all the advancement in building technology and think of who is left to perform this kind of work you have illustrated so well. Keep it up, we really appreciate all those who share the passion for the craft.
Thank you, Sarantos. I agree. Trade school could help shorten the learning curve that we all undergo in the trades. At the same time, experience is still the best teacher. Sometimes I think I learn the most when I screw something up and have to fix it. Also, I have had some excellent mentors. I can’t thank them enough for teaching and showing me so many good construction/carpentry habits. As far as the outside corner of the cedar siding being the same math as the prow facia…..there might be some similarities, but I don’t think it’s all together the same math. If you’re up for the challenge, you should check out the link that Sim Ayers referred to in his reply above.
I’ve still been running that tipped prow detail over in my mind; particularly where the two rakes transition. I like the architectural effect of the “tip” (even if angle is slight) on the fascia; but it seems it would present a dilemma with a clean transition on exposed finished framing. I say that because of the oblique angle created with the top “tipped” fascia joining into the lower “plumb” fascia section. I haven’t mocked it up with actual stock (and Lord knows I wish I could in sketch up), but it seems that you would only be able to mate up the front of the mitre joint…and not the back. In other words, it seems you would have had to “shave” an edge of (one stock or the other) on the backside to make the stock appear to plane out in thickness. Is that right?
At 6 degree it might be minor; but on more pronounced projections it could be substantial. I was curious if the desire to make this transition break “square” instead of “plumb” was an effort to minimize this oblique angle transition discrepancy?? I say that because I’m assuming that the plumb cut is a longer joint…and the longer the joint hits at an oblique angle…the bigger the discrepancy in stock thickness. Is that assumption correct? What would have been most interesting (to me) is to see how you handled that transitional joint detail (rather than the ridge cut), because the ridge seems to be a more straight forward, mirrored condition.
Thanks again for a great article that shows a couple different methods. I believe we all can learn in some way or another from the great articles we get here and all appreciate them. We call them “turkey tails” here and usually whack them off of old barns when we put tin on them because the customer wants to save a little money. They do add some character to the barn though and we do save them for renovation style work. Some food for thought on the tipped fascia: Since you know the bottom angle why not cut it long, screw it in place and then use a level to get it close to the bevel and miter on top? You can eyeball the bevel in with the ridge outlooker then a plumb mark on the face for the miter.
Thanks, Evan. Yes, I agree, you can use levels and strings to find these angles ( and trust me, I have). We refer to this as the “hunt and peck method” where you make some pencil marks and cuts……and then keep modifying them until they fit. This method is always my fall back method and it works. But, whenever possible or necessary, I like to know as much about what I am building before I am in position, especially when I am 20 feet off of the ground. It sure helps me to have my miters and bevels at least close to accurate before I’m up on a ladder or platform.