Shed dormers on a 1-1/2 story with site built trusses.

[lonelytree]

Folks,

In an effort to gain more usable space in the loft I am thinking about putting 1 or more shed dormer(s) in. Is this possible with the site built trusses or do I need to stick frame the roof?

Size 20W X 24L, 10 foot walls.

Any pics of this would be much appreciated.

Thanks,
Mike

[John Raabe]

You can use the truss layout to support a shed dormer. See sheet 11-20a in your plans booklet. There is a diagram there with a shed and gable dormer framing layout. It shows a stick framed roof with doubled rafters. You can provide the same base for the dormer side walls by doubling up the truss framing members. You will want to stick frame both sides of the dormer roof opening and hang a ridge board from metal hangers supported off the two doubled trusses. Tie the dormer roof to the opposite steeper slope with ceiling joists as shown in the diagram. This will lock the two sides together.

[lonelytree]

John,
   Thanks for the reply. Sorry that I missed the reference. What would be the largest shed dormer that I can use? I would like to go 8 or even 10 feet wide. Is this possible? Snow load can be a problem.

Mike

[John Raabe]

If you go over 8' to 10' there may be reason to go to an LVL ridge beam - especially if you want a cathedral ceiling. That could involve checking with a local engineer or the county plan checker.

However, if you have a sturdy 2x10 or so for the ridge board and tie the rafters on both sides together with well nailed continuous ceiling joists then the loads are triangulated and the shape is locked down. It would take some considerable forces to change that.