How to extend bottom chord of attic truss out beyond exterior wall?

[Dingeling]

Hi,

By default, CA generates a roof where the bottom chord of the roof truss is only as wide as the two walls it rests on. The rafter tails extend to create a roof overhang, which can be boxed if you want.

I would like to utilize the attic space to create additional living space, and to increase the available space a little - particularly the height - I'd like to extend the bottom chord of the trusses out 500mm beyond the walls they are resting on. (The extended bottom chords would then automatically create the boxed overhang effect, without need for rafter tails).

How do I do this in CA?

[David J. Potter]

You can use the "raise off top plate" setting in the build roof dialog, set for trusses, set truss defaults and then build roofs, then draw trusses.
It is not been discussed for many years but the truss poly-line of a truss can be edited in the "Truss Detail" CAD Detail Window, after creation.
The "Truss Poly-Line" is formed by the space created by the space between the ceiling platform and the roof planes, trusses then fill up that space when drawn, so the space determines the truss, over and beyond just settings.
You may be able to get exactly what you want by settings alone (not sure in detail exactly what it is that you want to end up with) and beyond that trusses can be manually edited to get just the look you want, the main limiting factor is your initial set up settings and the space you create (the attic cavity) than then dictates truss outcome.

DJP

[Dingeling]

Thanks David.
Sounds complicated, but I'll have a play around and see if I can get it to work.

[Dave Pitman]

What you want is to create a cantilevered truss condition. I think CA has a video on this, and there have been recent threads relating to this that you can research here.

[HumbleChief]

What you want is to create a cantilevered truss condition. I think CA has a video on this, and there have been recent threads relating to this that you can research here.

Yeah it's video 348 - pretty good stuff. To the Op if you don't have SSA and access to the videos you basically frame your roof higher than the plate



and adjust height till the height creates the cantilever you want. Remember you have to redraw, move or otherwise recreate the truss with each change to reflect that change.

[SkagitDesign]

Good new tips for me in here that I will try.

What I have done for a cant' is just use a deck railing. Put your deck at four feet, make sure it has a roof over it, and build the roof. You then have a four foot cantilever.

[HumbleChief]

Good new tips for me in here that I will try.

What I have done for a cant' is just use a deck railing. Put your deck at four feet, make sure it has a roof over it, and build the roof. You then have a four foot cantilever.

But don't you then have a deck railing as well? Do you hide it somehow, in case you don't want a deck railing?

[Dingeling]

Great tips; thanks guys.

[SkagitDesign]

But don't you then have a deck railing as well? Do you hide it somehow, in case you don't want a deck railing?

Older thread... But in that instance I would use a Straight Deck Edge. It doesn't produce the railing, but gives all other attributes of a room.

[Curtis Johnson]

To create additional space in the attic area, you may want to add another floor. In the process, depending on your roof pitch, you can raise or lower your roof to the required elevation. Once you have the roof where you want it, Chief will create an attic truss for you to create the living space. Trusses are created manually by selecting the truss tool and then dragging from eave to eave.

If your attic is going to be living space, you'll need to meet the required ceiling heights specified in the code. Keep in mind that the depth of the ceiling framing (i.e., the floor of your attic or 2nd story room) may be greater than a 2x4 or 2x6 where attic trusses are used. I have seen different bottom chord depths used for individual attic trusses .... deeper where the living space is and shallower in the attic areas on each side. Some attic trusses actually use a top and bottom chord for the floor framing where the living space is located. How the truss will be built will depend on all of your projects roof and floor specs.

Therefore, when you set up your floor platform heights, make sure you are using what the truss manufacturer will be specifying for your project. You can wing it initially (if you don't know) but you may have to adjust those values later before you complete your final design and CD's (after the truss manufacturer has provided a truss design package).

There should be a video on attic trusses if you have SSA. Scott Hall may have done one on Chief Tutor as well. As mentioned, there are prior threads that go into this subject as well.