Low Slope Roofs
A roof is considered to be Low Slope when the pitch of the roof is below 4/12 down to and including 2/12. This means that in a horizontal line 12 feet across, your roof would have to rise between 2 feet to just under 4 feet vertically for it to be considered a Low Slope roof.
Because Low Slope roofs don’t shed water as quickly as steeper roofs there is a higher chance of leaks caused by water deflection, wind driven rain and backup due to ice dams. Therefore the building codes and the manufacturers require special applications when doing Low Slope roofs.
There are basically 2 different applications designed for Low Slope roofs. The intent of each application is to provide a 3 layer roofing system to give added protecting against leaks. These applications replaced the 3 ply low slope shingles which were discontinued in the mid-nineties.
Application # 1: Install drip flashing and 2 courses of ice & water membrane at the eaves edges and 2 layers of #15 felt over the balance of the roof. This application is used by Dr Roof on roofs less than 4/12 down to and including roofs that are 3/12 in pitch.
Application # 2: Install drip flashing at the eaves edges and ice & water membrane over the entire roof. Then install one layer of felt over top of the ice & water membrane. This is the preferred application used by Dr Roof on roofs below 3/12.
Low slope roofs, by nature of their design and typical age, are prone to ice dam and condensation related problems, especially those with cathedral ceilings. These types of leaks are caused by heat loss into the attic or ceiling cavities due to poor or degraded insulation and poor or nonexistent vapour barriers. Leaks that materialize in the winter or spring thaw are not workmanship related roof leaks and are not covered under warranty.
If you have experienced any of these problems in the past please discuss them with your estimator and he can recommend a possible solution. We have corrected many of these problems using polyurethane foam insulation.
Also be aware that the life expectancy of shingles on low slope roofs is lower than steeper pitched roofs. Some manufacturers reduce their shingle warranties on low slope roofs and some shingles have no warranty on 2-12 pitch roofs.
Please feel free to call us to discuss low slope roofs in more detail.