Boston Gable Made Easy

If you are like me you are always looking for different, faster, and more productive ways to work. Here is a method I stumbled upon for quickly inputting the filler webs needed in a Boston gable truss. A Boston gable is a gable truss that has other trusses or conventional framing attached to the side. Instead of the field applied framing to support the sheathing and flashing at the intersection of the sloping plane and the vertical plane (the gable face), the blocking can be installed by the component manufacturer. So, let’s look at a quick way to accomplish this.

First of all, I’ve highlighted my Boston Gable truss below. There you can see that I have two runs of gable trusses tying into it on each side and a plane sloping up to the gable truss in the middle.


When I first input the truss it came in, as I would expect, with the top chord following the profile of the main span. For the first step, I’m going to modify the top chord. From the left end of the truss to the right, I’ll click on the planes in front of the gable truss. Here is the result; I’ve highlighted the modified top chord. This effectively gives me the centerline of the blocking I’ll be installing.


Next, I’ll import the modified truss into engineering and save it outside of the job folder. No need to analyze.


Once it is saved I will go back into Sapphire and modify the truss so that it has the correct top chord.


This client wants us to match the webbing of the truss just behind the Boston gable, then stitch the filler blocks in between the webs. So, after re-importing my Boston Gable truss I use the match webs tool with the adjacent truss.


I save, close out of the truss, then re-open it to lose the “shadow” of the truss I matched. Next, I’ll match webs again, this time I match with the template that I saved outside the job folder. You’ll notice that it messes up your webbing.


Just click undo and it reverts the webs back to where they should be, but the outline of the template remains giving you the profile of the roof planes tying into the face of the gable.


Sometimes the “shadow” of the template makes it hard to place the webs correctly. If needed just put in some reference lines along the top chord of the outline. Save the profile, close, then re-open. Once you go back into versatruss you’re reference lines will still be in place but the outline has been removed so that you can stitch in your filler cleanly. I leave the input setting at center and install all my filler. It comes in as 2×4 and will need to be 2×6, but I will leave that for now.

Next, you will want to change the properties of the “webs” that you have installed so that it is considered “non-structural” and not factored into the loading of the web members. Once this is done you can go through and make the filler pieces 2×6 if needed. If you happen to change to 2×6 first then change the properties of the fillers the filler pieces will all switch back to 2×4. So, change properties then size. Go ahead and analyzed the truss to make sure you’re filler is truly filler and not treated as a structural element of the truss. If you get funky errors chances are you have missed a filler piece. Turn analog on if you have trouble finding it.


Now it’s just a matter of inputting gable studs in above the filler pieces according to my client criteria. Any studs that come in below the filler pieces can be deleted. In this case, there is a 24” diameter Gable vent that I need to account for and I need to make part of the top chord 2×6 for notching in the field.



There you have it. Hope you all find this technique useful. How do you perform the same function? Any tips you can add? Let us know below!

Tim Hoke – Design Manager

Gould Design, Inc.