how many layers of shingle maximum can be put on a roof before its too heavy of a load? because i already have two layers on it, and don’t know if its ideal to put over the third layer.
Depending on the city that you live in it could be 2 or 3. I dont suggest going over 2 layers and some of the manufacturers dont either. Best advise i can give you is to tear it off and it will last alot longer. A typical 2nd layer will only last half the life of a tear off so with 3 which is illgegal where i am could be even less. With a tear off it will last close to the warranty as long as the ventilation and installation is done correctly.
Like gtp1003 stated, it is not wise to go over two layers. However, as far as the legality, it depends on where you live. I can tell you most places don’t want more than two layers of shingles on a roof, but will allow it if you get a structural engineer to sign off on the roof as being able to support the load of a third roof. Now, with that said, I don’t recommend installing a third shingle roof on a building let alone a second. I personally hate roof-overs, and always try to dissuade my clients from installing a new roof over a failing/failed roof.
hello john doe,
if your goin to put a third layer on you may want to consider a 5 v crimp metal roof.
the third layer of shingles usually gets very lumpy and doesnt hold up as well/last as long. not to mention hard to get fastened well.
the metal roof can use the proper length of scew to secure all three roofs
very well, a good thing if your in high wind area.
5 v crimp metal roofs, performed the best in the hurricane hit areas i visited over the last ten years.
homestead, vero beach, punta gorda, the 5 v crimp was the only roof material that you would find not blown off.