Whether or not to lay new shingles is a question that affects most homeowners. The decision to go for older asphalt shingles or to lay an entire set of new shingles is a matter of opinion that is best left to an expert.
Asphalt shingles
Asphalt shingles have an ideal lifespan of about 15-20 years. Ideally, homeowners tend to install three layers of shingles for extra protection from inclement weather conditions. Before installing the third layer, it is important to tear up the first two layers. It should be noted that professionals are not entirely comfortable in laying a second layer over the first, for several reasons.
Laying the shingles
It is extremely important to inspect the first layer thoroughly prior to installing the second and third layers. Repair or replace the entire first layer, if you find cracked, damaged or uneven shingles. This will ensure that the second and third layers are installed appropriately and well balanced.
The structure of the frame is another factor that needs to be considered. The roof must be able to support the weight of multiple layers of shingles. Get the structure inspected by contractors. If they feel that the weight is too much, they might recommend getting rid of a layer. If the roof structure is still considered to be weak, the contractors might advise you to skip the shingles altogether. However, if you still want to proceed with the shingles, you have the option of strengthening the structure. On the other hand, it should be noted that professionals do tend to advise against installing a second layer, even if the structure is strong enough to hold three layers of shingles.
