Author: Bryant Brockett
Yes and no, depending on the roofing system. Metal roofs may be a good option for laying over the existing roof, saving you time and money. On the other hand, I would never recommend putting a second layer of asphalt shingle over an existing asphalt shingle roof. The initial savings from not tearing off the existing roof will not compare to the money you will lose long term. The new layer will only last a fraction of what it should by not removing the existing roof.
Having multiple layers of an asphalt roof will cause the shingles to overheat and break down much faster than normal. Expect a 30-year shingle to only last 7-10 years at best. Another thing to take into consideration is that it is very difficult to repair an asphalt roof that has multiple layers.