When it comes to roofing projects, many homeowners are unsure as to whether or not they should have their asphalt shingles removed before laying new shingles down. The question is usually a matter of opinion held by the roofer. Generally, asphalt shingles have a lifespan of about fifteen to twenty-five years. Also, it is common to place two layers of shingles on top of one another, before laying a third layer. The general rule is to tear up both layers and then lay the third layer down fresh. However, a professional contractor may not feel comfortable laying a second layer of shingles over the first layer for several reasons.
First, the layer of shingles should be thoroughly inspected by a roofer before the decision is made to place a second layer over the first. If the first layer is severely damaged, cracked, uneven or buckled, then it is not recommended to lay a second layer over the first. The reason is simple. The new layer of shingles will take on the same appearance as the first layer. If the first layer is uneven or doesn’t lay flat, the second layer will fail to lay flat as well. For this reason, a roofer will not install the second layer over the first.
Another factor to consider is the supporting structure of the frame. The roof must be able to support the weight of multiple layers before installing additional shingles over the existent layer. If the roofing contractor feels that this is too much weight, they will recommend removing the first layer. This also includes the performance of the underlayment. If the supporting structures are not solid or sound, then the roofing contractor will not advise installing shingles over one another. However, even with a perfect roof, very rarely will a roofer recommend installing a layer of shingle over two layers.
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