Many homes in the Phoenix area that were built in the ‘60s and ‘70s used a grade of plywood that may weaken significantly over time. It is not always possible to determine the extent of this weakening until the existing roofing materials are removed. Some of these homes may require all new plywood if the problem is severe but this is not very common. Homes built prior to the ‘60s likely have the older style 1″x8″ decking boards. This type of deck usually has some large knot holes that may cause some of the boards to crack and those will require replacement. We recommend budgeting additional funds for wood replacement when you plan for your new roof. Although we cannot tell you exactly how much wood will need to be replaced until the roof deck is exposed, Glendale Roofing can offer assistance in setting a budget range based on our past experience, leakage history of your home and a visual inspection.