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fauer 09-26-2007 02:49 PM

Gambrel Truss Dormer and Ladder Framing?
I am buying gambrel trusses, and dorming out a section of the roof. Truss company explains I border the dormer area with a double truss at the beginning and end of the dormer. The floor joist in this area go perpendicular to the joists built into the trusses.

I can't quite picture completley the rest of it though, especially the roof gap opposite of where the dormer wall will be. I was told I would "ladder frame" that. I think I finally got the picture...more framing perpendicular to the trusses.... and in each case running from truss to truss lateraly.

Do I have it? How about size of boards/lumber to make this horizontal run from dormer start truss to dormer end truss?

crecore 09-26-2007 06:19 PM

Sounds like you interpreted what they said correctly. The doubling up of course that's how they plugged it in their little program. Probably overkill but it was easier than making special trusses there and besides you're paying for them. :laughing:

Depending on the span, it would be a LOT easier to run a regular floor joist between the doubles. Of course the bottom chord of the truss is probably not as tall as a regular joist for similar span so then you'd have a floor or ceiling height issue. Hence the ladder. IF they didnt specify, just look up the span (dormer width) on a joist span chart and use KD. Probably a 2x6 or 2x8. I would suggest prenailing all of these to one of the trusses before installation. This would be a lot easier on the ground and you also wont have to nail through the double truss on one end at least. Use a spacer block and toenail the other end in place.

Now, depending if this is a full open gambrel or it has a horizontal tie, knee walls, etc... you could consider running a short ridge beam between the doubles and raftering down the opposite side (where there's no dormer). You could also make a dormer header and run a rafter down to that so you dont have to ladder in everywhere. This is less time consuming, less material and will allow air to flow properly on the back side.

got it? :huh:

fauer 09-27-2007 07:04 PM

thanks so much!
You helped me a lot, thanks. I think I have a handle on it now...may have a question or two about the header idea later.
I am now thinking of just doing dormers on both ends of the void (where there are no trusses). If I have to do sizing and nailing there, why not just make it into another dormer! I know, that's a lot more than the ladder framing, but I'm tempted.
I sure hope I find the courage to work at that height!

crecore 09-30-2007 07:36 PM

No problem. Dont forget all of your horizontal and diagonal cross bracing and/or purlins before you're up there fooling with the dormers!

good luck

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