It depends on what you are planning to do. If you are simply applying a new layer of shingles you do not need a building permit. If you are replacing or repairing any portion of the wood sheathing supporting the shingles or structural members like rafters or trusses, a building permit is required. You might need to obtain a Certificate of Appropriateness (COA) if your home is located in a historic district. When recovering an existing roof, the new roof covering cannot be installed without first removing all coverings when the existing roof has two or more layers of any type of roofing to keep from overloading the roof structure.