Hi from Mississauga, ON

[John Das]

Hi folks.
I stumbled on your web site trying to do some research on my roof/attic. I need new shingles, and one contractor said that the roof deck was soft, and I'd likely have to replace 40-50 sheets of plywood due to mold.
My house was built in 1986. Previously re-roofed in 2000. About 1000 Sq. Ft. total attic area. 4 sided roof, 4/12. 7 or 8 soffit inlet ports. 4 roof attic vents. 1 East, 2 south, 1 west. 3/8" plywood near as I can tell. Trusses on 24" centers. Plywood looks normal to me for it's age. I can't see any obviously damp areas. Some nails have some rust stains. Rafters have some brown areas that look like normal aging, but no mold that I can see.
Any opinions?

For some reason, I can't upload pictures.

[Raymond Wand]

Twenty-four inch O/C and 3/8 decking are the cause, very common.

Best time to check attic for condensation is on a really cold night. Check attic with strong light and look for frost forming on underside of deck.

Ensure all soffit vents are open, not covered with insulation.