Is a Metal Steel Roof Overlay a good system?
The roof above is one I recently looked at for a potential buyer of this property. It is a stone coated steel roof installed over a cedar shake roof approximately 15 years old located in far North Dallas. Normally I would expect a Stone Coated Steel roof, such as Decra, to last well over double that 15-year life.
So why were these buyers wanting an estimate for a new roof? Because six major insurance carriers did not want to issue a new policy on this property simply because it was an overlay. This is a silly position and has zero basis in how this roof system will perform now and into the future.
Overlay roofs are typically an asphalt composition shingle over a cedar shingles. This type of overlay has some well-warranted potential problems. The cedar is soft and irregular making damage from hail significantly more likely. You can see why insurance carriers would rightfully shy away from this. Not only are asphalt composition roofs over cedar easier to damage, the replacement of them involves a much larger scope because a new deck must be installed before a new asphalt composition roof.
The metal roof overlay of a cedar roof is nothing at all like that of an asphalt composition overlay. Stone Coated Steel is typically installed over a batten system of two by two lumber. This same batten system is easily installed over a clean deck or (with a few minor additional steps) installed over an existing cedar roof. The metal roof is installed on the bats all the same regardless of what the bats are attached to. The metal roof’s performance is exactly the same as well.
So what is the real problem with a Stone Coated Steel roof over cedar? Really, not much at all …… unless you a trying to find an insurance carrier who knows the products on the house you want to buy.
Update: recently ran across this exact same issue on a different house, this issue killed the sale of the property.