Roof Plywood Delamination

One of the implications of high moisture levels from either condensation or leakage is delamination of plywood sheathing.

Roof plywood delamination.

When the membrane and insulation separate. Delamination often occurs due to excess moisture. Every re roof requires a close inspection of the substrate. I had my roof sheathing replaced a year ago.

Plywood oriented strand board osb and particleboard are all examples of laminated wood. Between the years of around 1964 to 1975 homes being built saw the installation of what was first generation fire retardant plywood. This plywood is ordinary cdx and had not been treated with a fire retardant. Plywood nailed to a wooden floor.

A bubble or lump on the surface of the wood is a sure sign of delamination. This is sometimes accompanied by buckling. Incidental roof leaks particularly ones that go unnoticed can delaminate plywood sheathing or cause osb to swell. Other plywood separations can be blamed on mistreatment of the plywood or failure to practice good woodworking techniques.

This winter i went up. It almost feels like flashing under it but its far enough away from the valley that i think it may be the plywood is delaminated and the top layer buckled up. If you can inspect plywood before you buy it you may be able to detect these common signs of delamination. Lamination is the process of creating a rigid product by compressing thin sheets or small pieces of wood together to form a larger piece using glue.

The worst cases result in patches of rot. Delamination can occur when plywood gets wet. It was plywood and had delaminated. I was on my roof today blowing off debris from a wind storm.

The contractor thought it might have been due to excess moisture in the attic. Roof decking plywood delamination. Panel type roof sheathing may lift off the rafters in a regular pattern. If you have a home twenty five years or older you may want to consider the condition of the plywood.

I walked on a section about 1 2 the size of a garbage can lid that felt like the shingles were buckled up. Like blisters delamination can come from improper installation in inclement weather. The plywood is delaminated and beginning to fall apart. Photo 1 shows the exposed underside of the plywood in the attic.

With its numerous layers plywood is prone to delamination if proper manufacturing processes are not observed. Delaminations commonly affect single ply and fully adhered roofs.