Expert: Dan Griffin - 5/17/2011

Question
QUESTION: What is the best procedure to fix a sagging roof (not on ridge line, but further down roof (6 to 9 ' further down from ridge)with a span of 24' with no support underneath?  There are weight bearing walls on each end of 24' span. You are facing ridgeline...not gable.  Thanks!

ANSWER: GiGi, you don't tell how far this condition exists nor what the existing rafters are.  We should also know where you are to help calculate snow load. Is there an attic where you can do some additonal bracing or is this a cathedral ceiling condition.  What is the roof slope now?

#2 yellow pine on 24" centers would have to be 2x12 to make the 24 span you tell that you have with minimum snow and wind loads.  Again, I don't know what you have.

It may well be possible to use an LVL or similar beam that is long enough to span the room in question and cut the rafter span in half.  This would require devising some method of getting the beam up in the attic space.  The bearing ends of the beam will need to have a load path to the footing(s).

If there are any other interior walls it might be possible to create a purlin brace to deal with the deflection.  Here is a simple explanation:
http://www.mcvicker.com/resguide/page010.htm

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QUESTION: Thank you for your time and answers.  Pls. consider that you are facing the gable and you only have half a roof or bldg.  In other words..at the ridgeline, go another 6" to the right and the bldg./roof is cut off there. It is a 3-sided carport..half the width of the home.  The 24' spans from gable to house.  The roof is sagging maybe 6' to 8' down from the ridgline.  The rafters are spanned, maybe 2' apart.  Located in upstate of S.C.  and there will be a new metal roof on it soon, but we have to fix the sag first. Finally, sld we use steel beam or LVL? Thank you!

Answer
gigi, I am sorry, but I cannot envision the issue.  Is there any way to send me a picture?


If my original suggestion does not fit, you might consider jacking the negative crown out of the rafters and sistering additional rafters to the originals.