Before we start installing Shingles or Flat Roofing materials, we make sure the roof deck is in good condition. Roofing material manufacturers recommends a minimum of 3/8 inch plywood, however, thicker is better.
On a lot of older homes in Toronto we encounter wood board roof decking. They must be retrofitted with wood that is nominal to 1 inch thick. Wood boards are prone to buckling and rotting because of their age. At times, we may have to go over them with plywood or take off the rotten wood, retrofit and cut the new wood, and re-nail it.
You can put the best roof down, but in the end up the day if the roof decking isn’t solid enough leaks may happen! We know this because we have been called in to repair these type of roof leaks in the past.