In almost every situation, the answer is yes; a new metal roof can be installed over an existing shingle roof. Since the installation of a metal roof doesn’t require the old shingle roof to be torn off, metal roofing has grown very popular. By not removing old shingles, homeowners save hundreds of dollars (less time-consuming and less expensive).
Metal roofing doesn’t add much weight to your home
Metal, while extremely strong, is incredibly light, weighing less than a pound per square foot compared to up to four pounds per square foot for asphalt shingles. The addition of a metal roof over existing shingles does not significantly increase the overall load on the home structure.
Metal roofs are another layer of insulation
Installing a new metal roof over an existing roof not only saves the cost of completely removing the existing roof, but it also provides additional insulation above your home to prevent heat and cold air from escaping.
Since we’re talking about insulation, we should mention that metal roofs are heat-blockers, meaning they reflect heat away from their surfaces rather than absorbing it. This means that the additional insulation from your shingle roof will not act as a heat trap for heat emitted by your metal roof.
Considerations for installing a metal roof over shingles
- In most cases, what we said about installing metal over shingles is correct. However, it is always a good idea to check with your local building and zoning departments to ensure that metal-over-shingle installations are permitted.
- If your shingle roof is leaking, look for rotting rafters or sheeting. These issues should be addressed before installing the new roof.
- If the current roof’s weight has caused structural issues such as buckled trusses or sagging decking, these issues must be addressed before new installation can begin.
- It’s usually a good idea to add some type of underlayment on top of the shingles to keep the granules from contacting the metal and causing corrosion. Your metal roofing contractor will inform you of your options in this regard.