need to replace soffit and facia on a 1962 Georgia beach house…..warm and damp zone 2. Rafters are 24″OC. Review of Azek installation instructions indicate 16″OC needed. So…due to existing roof overhang my facia backing would be installed between rafter tails. Soffit backing calls for 1/2 min ply. This is an unvented soffit.
question is ……will plastic installed directly to wood sub in an unvented space cause the wood to rot.
thanks
Replies
Plastics, per say, do not cause wood to rot. Sustained moisture conditions or repetitive wet drying cycles that allow untreated wood to maintain a moisture content in excess of roughly 19% will cause wood to rot. So if installation of your azek promotes or exacerbates this condition for your untreated wood materials, then you may want to re-think your plan. One alternative is to use solid pressure treated backing as insurance against rot.