Roof Decking & Plywood Delamination

If you have a home twenty five years or older you may want to consider the condition of the plywood. Particularly on the roof.

Between the years of around, 1964 to 1975, homes being built saw the installation of what was first-generation, fire retardant plywood. During these years, the construction of the sandwiched plys were accomplished using aldehyde-base glues - to which also, as it turns out, about 5% of the population is allergic. In rough numbers, three-and-a-half million houses are constructed in this way.

Over time, and given exposure to certain conditions, these glues have a tendency to break down, causing the effect of delamination - the separation between the layers of the ply. This characteristically takes on the appearance of a wavering apart in a sense and this greatly reduces the strength of the bond. The strength of the roof.

Delaminationa might be found from the deck underside, by walking the attic.

Checking for this might be done by an inspector or a structural engineer for the accessible areas.

This is a frequent problem for skilled roofers and this normally means a tear down. But get several opinions. (could also be in flooring/wall sheathing)