One question we are often asked is –
“Can you install metal roofing over shingles?”
The answer is, YES!
One big advantage to metal roofing is that it is light weight, which makes it the perfect material to be installed over an existing shingle roof. However, there are some things that you will want to check out before doing it this way.
For one, you will need to check with your local building department and ask if this is an approved installation method. More than likely they won’t just come out and say yes. They will want to make sure that the plywood the existing shingle roof is attached to is in good shape, meaning it has no soft spots.
The reason for this is so when the metal roof gets installed, the screws have something to bite into. Can you imagine screwing a metal roof, or anything for that matter, into rotten wood? More than likely the screws won’t hold and that is something you definitely don’t want happening if you want your roof to stay on during one of those afternoon thunderstorms we get here in Florida.
The Florida building code, which is the minimum building standards that buildings have to be built to, including roofing, says that you can’t have more than two layers of roofing materials on a residential house. The reason for this is that most house trusses, when engineered and built, are designed only to hold so much roofing weight.
If you were to put too many layers of roofing materials on a house, there would be a good possibility of the trusses failing. Some counties and municipalities require you to remove the existing roof regardless if it is the only layer of roofing on your house. This way the building department knows that the plywood is in good condition and can be reused for another roof.