Rafter Roofs and proper rafter seat cuts?

[Jim Merritt]

I thought I would find something on this searching, though didn't:

It appears from my current understanding of Revit that when you select the rafter option, it does drop the roof (lower that a truss roof) to account for the seat cut. But, it seams that Revit is using the full thickness of the wall (as apposed to the core thickness) to determine the seat cut size.

For example, I have a basic 2x6 core wall structure with 1/2" OSB on the exterior and 1/2" GYP on the interior. Rather than making the seat cut 5 1/2" for the core (stud) width, it is making the seat cut 6 1/2".

Has anyone run into this, or know how to get Revit to draw the proper sized seat cut? It seams to me there should be options within rafter roofs to know what layers of the wall it should be using to get seat cuts right. Thanks for any help!

--Jim

[patricks]

When you draw your roof footprint sketch lines, you need to select Extend to Core. That will snap the lines to the outside face of your core layer. Then specify your overhang distance from the outer face of the core layer. When you finish the roof and select the Rafter option, the lower edge of your roof's core layer will intersect the inside face of your wall's core layer.

You have to use Pick Walls with Extend to Core enabled for this to work. If you pick walls but do not have extend to core enabled, then the Rafter roof type will behave as you describe, putting the seat cut at the interior finish face of the wall instead of the interior of the core layer.

[Jim Merritt]

So *that* is what the little "Extend to Core" button is for.:mrgreen: That worked great, except now my 5 1/2" seat cut goes from the outside core of the wall to the underside of the GYP in my roof assembly. Maybe I need to not include the 1/2" GYP layer within my roof style? Any other options known for this? Thanks.

[patricks]

I'm guessing you're doing a vaulted or cathedral-type ceiling with sheetrock directly on the bottom of the rafters? To really model it correctly, you would need to do the sheetrock as a separate ceiling element. The catch here is that you can only have one slope per ceiling element, so if it's a double-sloping ceiling to match a double-sloping roof, you would then need 2 ceiling elements.

Or if you don't need to host lights from that ceiling, you could do the sheetrock as a roof element, but it would need to be separate from the actual main roof in order to have the sheetrock not go out past the exterior walls.