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When is it a ridge board vs beam with load?


krosspen's Avatar
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Join Date: Dec 2007
Posts: 45
WI

01-19-08, 07:15 PM   #1  
When is it a ridge board vs beam with load?

Inspector came today. He comes this one and only time on my garage w/Loft. Couple small things not a problem...and one hang up maybe. I had to rush with winter coming on and I went with gambrel trusses. I left 8' gaps between doubled trusses to leave space for dormers. Four dormers actualy (two 8' gaps).

The rafters are very substantial for the distance, a little over 15', and they are 16 on center 2X10s.. He's concerned with the ability of the trusses to hold up that ridge board/beam. I interpret it more as a ridge board (although it's double 2X10s), while he interprets it more as a beam carrying substantial load....to each of the rafter sets where the dormer begins and ends.

I have to put in some colar beams yet (I volunteered the idea, he agreed I should), and with them I see the places where the rafters start on the top as more of a ridge board, not carrying so much weight. I see them as a ridge board with the weight carried by the rafters.

I promised to find my truss layout drawings and fax that to him, but I'm concerned there won't be enough detail there.... It only shows the truss layout, although it was clear dormers were in the 8' gaps. I actually don't expect him to come back and create a big deal about this, but if he did I'd have a tremendous problem (how to support the "beam").

Top center of the picture is the rafters....you can see the trusses behind. Note lower picture too....
http://i82.photobucket.com/albums/j2...g?t=1200798883

 
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carpenter jai's Avatar
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Join Date: Jan 2008
Posts: 13

01-19-08, 07:41 PM   #2  
From what I can see by your photos, you have built a floor first, and then started putting roof trusses on that floor. If your trusses were engineered properly they will supply force (the roof load) over the exterior walls.

Then there are your dormers. All the loads in this building seem to be supported by the exterior walls of the first floor. What you have built your dormers on cannot be called a beam, because a beam is for spanning an area with no support. That is clearly not the case here, since the "beam" is resting on top of a floor directly over a load bearing wall.

If we're getting caught up in definitions then I would call that a rim joist, and a rim joist is not for carrying load, it's for attaching siding to. But in your case, it is supporting load, and I think more than adequately. I bet your inspector was just trying to find something to pick on since you used some building methods that don't fit inside a rigid and specific formula, ie. code. Code varies from region to region, but usually, if an engineer puts their name on it, it's good enough.

Either way, your building appears to be over engineered as far as I can see. I say, if you have trouble with this inspector, get your plans approved by an engineer and be done with it.

P.S. Not to be a pain, but is there something supporting the roof sheathing between the double truss and end truss. It looks like there is four feet of unsupported roof from the photo.

Jai

 
stpami's Avatar
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Posts: 61
MD

01-26-08, 08:01 PM   #3  
The ridge beam becomes load bearing if the rafters are not held both up, and in, at the foot. If the foot of the rafter moves, either by sliding out, or, by pushing the wall out at the top, the ridge will have to follow and will drop. In your case if your wing walls are suitably framed to provide structural rack bracing for the corners of the 8' walls, keeping them plumb, you should be fine. The 8' section is rather short and rigid as it is mostly header. With those sections tied in and unable to be moved your back to back rafter sections will actually be holding up the ridge beam although it should still be tied in with hangers, etc.. I would also tie the outside dormer rafters in to the adjacent truss to further immobilize it all.

 
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