This customer called us with a question we get alot. "Can we put another layer of shingles over?" The customer already had two layers of shingles on it and tectum decking under that. The home had some water damage inside. The roof integrity had been compromised and the shingles where about expired.
As a rule we never add second layers. Everytime the materials need to be tore down to the decking. In this case the customer had two layers that we tore off down to the tectum. Tectum recommends NOT to nail shingles to it, instead they recommend to install plywood to the tectum then shingles to the plywood. This is the standard process.
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