What is a roof pitch, exactly, and why does it matter? Your roof pitch, put simply, is the ratio of the rise of the roof and the run of the roof. It is important because the roof pitch determines the type of roofing system and materials necessary for your home.
The roof pitch can also be a determining factor of how long a roof system is estimated to last. How quickly and efficiently water and other debris are cast off of the roof plays an important part in roof longevity.
Flat roofing, for instance, (which is generally not actually flat), have a roof pitch that rises 1 inch for every 12 inches (1:12) or 2 inches for every 12 inches (2:12). A “flat” roof should not actually be flat because the water does need to be able to shed from the roof in some way. Anytime large amounts of water is left “standing” on a roof system a problem can be expected.
Having a flat roof limits the type of roofing material you can install on your roof system. A low slope roof system should not have dimensional composition shingles or tile installed on it at all. This is guaranteed to create a problem. This includes areas of a steeper pitched roof that has low sloped areas, these low sloped areas should have material made for low sloped roofs. In the past, “hot mop” or “tar and gravel” were the popular choice for low sloped roofing, but these materials are dangerous to install and have slowly been phased out by more modern technology such as PVC and TPO roofing. The best way to describe a PVC or TPO roofing is similar to a pool liner. This material is strong enough to keep water in, and strong enough (on a roof) to keep water out as well. When installed correctly, a PVC or TPO roof has a much longer roof life than products like rolled roofing, which is another common roof system that generally only lasts 5-10 years.
For a roof that is pitched greater than a 3:12, the proper roof material could be anything from any dimensional composition shingles profile around, or tile, standing seam metal, or metal tiles. Any of these options are sufficient for a pitched roof, but more consideration should be made before selecting a roof material. Roof pitch alone is not the single determining factor.
It is extremely important to ensure that the material being installed on your roof is suitable for the pitch of your roof. This is why you should always hire a reputable roofing contractor.