What defines ridge board vs. beam>

[FrankInWIS]

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....



Thoughts?

[MountainDon]

What does the truss manufacturer have to say about all this? I imagine they engineered the trusses to do the job correctly.    At least that's the way it worked here when I added onto the house. I gave them the engineered drawings with the permit request. Then the building permit folks went with that and the inspector hardly even looked up when he came through. Mine were a modified scissors truss, not gambrel, though they are both engineered.


To me a ridge board simply connects the rafters to one another and the "left" half to the 'right" half. A beam on the other hand needs to have a post at either end, and maybe additional supports in between to transfer the roof load down to the foundation. 

[ScottA]

If you're relying on the ridge to support the rafters then it's a beam. Do you have collar ties to form a triangle? Is the pitch greater than 3/12? If not it's a beam.

[glenn kangiser]

Seems to be a legitimate concern to me.  If it is not a beam, then the joists will push out on the walls with not much support.  Seems you will need to firmly support it to the trusses at each end also.

Say roughly 30 feet x 8 feet= 240 sq ft x 50 lbs PSF live and dead load round numbers =1200 lbs pushing the walls but with great leverage if the beam sags.  I'm not an engineer but do rough guess -- rule of thumb calculations for myself to see what might be happening to my structures.  Others may have better info.

I'm guessing that the two doubled trusses that would be in the window area have the strength to support the beam as they would have carried the load otherwise, but the point loads are now below the corners of the dormers.  With a slab - continuous? concrete footing I don't think that is a problem.

The collar ties may handle it fine.

[PEG688]

  The gambrel trusses appear to be doubled up , YES?? If so I'd think the engineering would show a dbl. 2x10 hanger to hang those ridge BEAMS, in. From what I can see of it they'd be beams.

Mixing stick framing into engineered trusses you get a sort of mixed use of terms. And like Scott said your pitch is so shallow on the stick framing collar ties would not do much for you.

  Look over your truss engineering package , or call the manf. and ask what they planned on , I bet a hanger was scheduled for those locations.

G/L PEG     

[FrankInWIS]

Scott A, it's a 4/12 slope on the dormers. 
Yes Glenn, monolithe slab. 
Yes PEG, doubled up trusses on edges of dormer.  What I got from Truss company was a drawing on exactly where to set the dormers.   Then there was generic document about how to use the trusses (i.e. nail pattern when doubling, but don't think there was anything about hangers to use.  I am gong back and putting those hangers in though.  Lost my papers and will contact truss company.  Good company to work with, I actually talked to the engineer a few times abous something else.
I imagine that the slope of the dormer was assumed to match the slope of the truss; but it doesn't, it's 4/12 and the trusses are a little more steep. 

Like I said, he could cause me trouble.... will shore it all up and send him some paper and hope he lets well enough be. Meanwhile, I WILL watch the dormer face walls that they stay perfectly vertical, and watch that mid room doesn't sag.

[PEG688]

 



Like I said, he could cause me trouble.... will shore it all up and send him some paper and hope he lets well enough be. Meanwhile, I WILL watch the dormer face walls that they stay perfectly vertical, and watch that mid room doesn't sag.

  Ahhh on seeing this photo you have the same thing on the other side ? One big tied together dormer? One each side that is. 

With the two gambrel trusses buried inside those "bigger" dormers , I know you'll not have problems with settling, the two buried trusses will hold it together along with the roof sheathing. I'd suspect inside you also have interior walls dividing the rooms at the buried Gambrel truss line???

With hangers at each end of your dbl'ed 2x10 your golden , I'm sure the truss company had "the whole picture" in mind when it was designed.     

[FrankInWIS]

yes Glenn, it looks like one  big dormer on the outside, but actually there are two sets of double trusses in the middle of that.  Makes a small portion of the inside un-usable, but yes it really beefs it all up.  The actual between the double truss space for each dormer is actually more lit 7'6".  The space in the middle between the two sets of double trusses is less than 2' 
Thanks very much for the feedback, I'm getting more confident I am in good shape. 
Actually the inspector put too stickers on the house.  One was "failed" and cited the trusses, then he put up the regular sticker and marked it "passed all rough in inspection".  I promised to take care of it and fax him info, and I think he won't be back as long as I send him something.

[PEG688]

yes Glenn,

That Glenn sure is helpful     

[FrankInWIS]

ooops PEG, YOU da man!!! 

[glenn kangiser]

I didn't even know I did that.  Good on ya, PEG.