[232323]

Any ideas what might cause severe buckling of roof sheathing? This house dates back to the 60's with 3/4" 1x8 pine decking. The boards dont appear to have come loose at the nails, but instead have cuped badly....1-1/2"- 2" in places. The worst area is over a full bathroom that doesnt have an exhaust fan or window and theres an attic access hole directly outside the bathroom door. There was a window in the bathroom at one time, but that was eliminated a few years ago. Its a shingled, hip roof with no soffit vents and only 2 small attic vents (apx. 1000sq. Ft.).
Im thinking the problem is related to condensation and lack of proper attic ventilation along with not having a bathroom exhaust fan that vents outside. Could this cause the roof deck to buckle...or are there other potential causes? Im stumped. Very extreme climate here...100+ in the summer...-30's in the winter.

 

[roofermann]

Moisture from that bathroom is the likely culprit. Need to instal a a vent fan ducted to the outside.

 

[jmiller]

You don't sound stumped, because you listed all the problems. 1 by 8 cups more easily than one by 6...

Install soffit vents and baffles ( intake NFA to equal or exceed exhaust in NFA), re insulate, and exhaust the bathroom fan to the outside. Tear off shingles ,replace the decking with seven sixteenths OSB. Put new singles on and they're good to go.

IIRC IBC Requires an operable window or bathroom vent in a bath, which is ludicrous because who opens the window in the winner to take a shower? All bathrooms need an exhaust that vents to the outside.

 

[jmiller]

Insulating the attic access is highly underrated toO.