Houses Built With 3/8″ Plywood Decking

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We see this decking most commonly on houses built in the late 1950’s into the mid-1960’s when plywood usage really entered the housing market in our region. Split-levels and ranch style houses are where we run across it the most. Often this plywood no longer meets our criteria as a solid wood deck.

Delamination of the plies is common from poor ventilation, moisture, thermal shock, and type of glue used in the manufacture. This drastically reduces the strength, which is already questionable due to its thinness. Sags between rafters and buckles are widespread as well as roofing nails popping out. 3/8” plywood can seem fine from inside the attic, but this plywood cannot generally withstand the “trauma” of roof removal. The use of 3/8” plywood is allowed by code in most municipalities if it’s already there, but it’s reasonable to expect considerable patching or problems if it’s not replaced. We usually recommend the replacement of this kind of plywood. A good roof starts with a good deck.