On Nov 13, 6:31*am, George wrote:
On Thu, 12 Nov 2009 06:45:39 -0800 (PST), Big_Jake



wrote:
On Nov 11, 8:54*pm, George wrote:
On the current series of This Old House, they're (among other things)
putting a two-story, one-room-wide-ish addition on a house. *The
addition has a gambrel roof, at right angles to the main roof.

For the ridge on the addition, they're using a double 2x12. *This seems
kind of massive, to me. *For instance, our (old) barn (not large, but
way bigger than their addition), also has a gambrel roof, and just *a
1-x-whatever for the ridge board.

I'd be interested in any thoughts on this.

Thanks,
George

I would guess that your barn didn't have a cathedral ceiling, and that
their addition did. *Their ridge is a structural ridge, holding up the
roof, and needs to be pretty big, especially if a snow load is
involved. *A double 2x12 is on the small side. *We have a 20' long
addition on the back of our house that has a double 14" Microlam as
the ridge.

JK

OK, thanks. *Just to clarify: with collar ties (and suitably-sized
rafters), the ridge load would be much lower? *When you say the ridge is
holding up the roof, does that mean their rafters are in tension?

Thanks again,
George

The ridge load is really nothing. It is being held up by the
rafters. And you are correct that a structural ridge puts the
rafters are in tension (I think).

I am not a structural engineer, but I did point out a math error to
the one that did the calcs for my addition, causing him to change the
footing diameter from 6" to 18"!

JK