However, by mid 1988, it became apparent that a large-scale problem was developing with FRT plywood roof sheathing in that it was deteriorating to an unsatisfactory condition within several years. It is estimated that potentially defective FRT plywood was used in roof sheathing on over 1,000,000 housing units. Moisture or humidity that may be present in an attic space claimed by some experts to be a major contributor to deterioration. Re-drying at temperatures above 150F, following FRT pressure treatment. This can indicate serious strength reduction and degradation of the plywood before it is ever placed in service.
Several producers claim that they have had such a product.
This variation makes it extremely difficult to assess a particular situation without an in-depth evaluation. The current problem with certain FRT plywood roof sheathing can be summarized as severe strength loss or deterioration of the plywood within several years of installation under typical environmental exposures in the roof. Exposure to elevated temperature conditions, as in roof sheathing, can initiate the chemical process designed to resist flame spread during a fire. Degradation of this type occurs in all FRT wood subjected to extreme heat with sufficient moisture present. The rate of the reaction, which is controlled by temperature, determines whether the wood will retain sufficient strength for the life of the structure.