At first glance, it may seem pretty obvious if your home has a steep or low sloped roof. However, there is an actual definition and whichever category your roof falls into dictates which type of roof covering should be installed. Or, at the very least, what steps must be taken to ensure your roof is water tight.

 

First of all, you need to understand roof slope is the ratio of vertical inches of rise to horizontal inches of run, typically expressed as “X in 12” or “X:12”. “X” can be any number of inches (e.g. 3:12, 4:12, 12:12, etc.). A 4:12 roof will have 4 inches of rise for every 12 inches of run.

 

Roofs are generally grouped into two categories – low slope and steep slope. Low slope roofs are defined as having a slope less than or equal to 3:12 while steep slope roofs have a slope greater than 3:12.

 

Low sloped roofs should be covered in waterproof, impermeable coverings. Low sloped roof systems typically fall into one of three classifications: built up, modified bitumen or single ply. Each, when installed correctly form a continuous waterproof membrane.

 

Steep slope roofs are most often covered in water shedding (not waterproof) roof materials. Steep slope roof systems commonly fall into one of these five classifications: asphalt shingles, clay or concrete tile, metal, synthetic or wood shake. Of course, within each of the classifications listed, there are often sub classifications too.

 

Here, in Hawaii, roof coatings are also very popular, primarily due to them being an inexpensive, less labor intensive option. I didn’t include them in any of the classifications listed above because they are not intended to be stand-alone roof systems. They are most often installed over existing roof membranes and are meant to be used as a maintenance covering to extend the life of your existing roof membrane.

 

More detailed descriptions of each type of roof system will be provided in future posts.