Monday, July 26, 2010

Sugar House plans 10 -- Locating the trusses on the top plate

Now that the walls are complete, it's time to start putting up the trusses. Be sure to consult a local professional on how to work safely on a roof with a pitch this steep. There are lots of good roofing books available with information you'll need if you want to tackle the job yourself.

If the steep pitch seems too daunting, or you're not sure you can do it safely, by all means hire a pro to do the job.

As you may recall from an earlier post and in the roof details video, we are numbering the trusses 1 through 7, left to right, as viewed from the front. This will help us with marking and positioning them on the top plates of the Sugar House walls.

First things first, though. If you're going to install some sort of flooring in the loft, now's the time to attach a joist to the inside of the rake walls. It's cut from a 2 x 6, and aligned flush with the rake wall's bottom and lower corners.

The rake walls will be positioned centered on the side walls, with an inch of overhang front and back. This side view shows the positioning. (The rake wall joist is also shown here.)

Here's how to mark the positions of the trusses and rake walls on the top plates. Note that there are some differences in dimensions between the front wall and rear wall. The center truss (number 4) does not rest on the front wall. And the gussets are eliminated on the inside front surfaces of the doubled trusses (numbers 3 and 5). Here's the rear wall:

And here's the front wall:

Here are the dimensions for the header for the dormer rafters. It's cut from a 2 x 12. You'll need to install this between doubled trusses 3 and 5, before installing the center truss number 4. This will provide a nailing surface for the center truss, which is trimmed in the front to allow for the dormer. You will also need to install a crosswise joist between trusses 3 and 5 to nail the lower chord of truss 4. You can follow the plans if you like (see the post on roof truss dimensions), but ultimately the location of this piece, and the length of the lower chord of truss 4, is up to you, depending on how large an opening to the loft you desire.

As you position the trusses and rake walls and plumb them, temporarily nail 2-by's at angles across the surfaces to hold them in place until the roof decking is installed.

Install blocking between the trusses along the tops of the front and rear walls. Use the truss layout diagrams above for lengths. Cut the blocking from 2 x 8 material. This will allow a gap under the roof decking for ventilation. Install galvanized screening in the gap later. Do not install blocking between trusses 3 and 5 in the front. That's where the dormer framing will be installed. The blocking should be installed flush with the front of the wall framing and front edges of the gussets, and vertically plumb. Hold off on installing the last piece of blocking on each end until after the verge rafters are installed, which we'll cover in the next post.


Merrill said...

I love it! I have looked all over for just the right tiny building. This is it!

Walt said...

Glad to hear it, Merrill. Thanks!