Double coverage refers to a method of shingle installation where two layers of shingles are installed over the same area of the roof. This technique is sometimes used to increase the thickness and durability of the roof covering, and can provide additional protection against water infiltration, wind uplift, and other types of damage.
Double coverage is typically achieved by installing a base layer of shingles over the roof deck, followed by a second layer of shingles that is installed over the top of the first layer. The second layer of shingles is typically offset from the first layer to ensure proper alignment and to avoid creating a ridge or bump in the roof surface.
While double coverage can provide some additional protection against the elements, it is not always the best solution for every roofing situation. In some cases, double coverage can increase the weight and load on the roof structure, and may not be recommended for roofs that are already at or near their weight capacity.
Overall, the decision to use double coverage in roofing should be based on a careful consideration of the specific needs and requirements of the building, as well as the type of roofing material being used and the climate and weather conditions in the area. Proper installation and maintenance of the roof system is essential to ensure its continued durability and performance, regardless of the method used to install the roof covering.