Low slope roofs with shingles

Reroofing is a big and costly project. Due to this, many homeowners decide to carry out the reroofing themselves, but they may not be aware of the limitations of their shingles. One of these commonly overlooked limitations is the slope or pitch of the roof and the shingles’ ability to shed water downward, especially in the winter when cold temperatures can cause freezing on a roof and create ice dams. These dams can hold water into roofing materials, which can melt between shingles and cause water damage to roofing materials.

Roof slopes are expressed as a fraction out of 12 to make it easy since 12 inches is a foot. For instance, if you have a 12/12 roof, it means that for every foot or 12 inches across the roof, it will slope up an equal 1 foot, giving an angle of 45 degrees. When installing shingles, the lowest slope that should be used is a 4/12 slope, where for every one foot across the roof, it only moves up 4 inches. But there are certain procedures that can be taken to better shed water at these lower levels. For a roof with a slope of 2/12 or lower, shingles should be avoided altogether as these are considered flat roofs, and they won’t be able to shed water well enough to protect materials under the shingles.

As a home inspector, we are unable to see what is going on under the shingles, but we will call out low-slope roofs and the possibility that they may have been installed without using the necessary methods to protect the roof below. based on signs that we find we can better prove that installation was not carried out following the extra steps needed. When a roof is called out with a low slope one of the best ways to ensure that it was installed correctly is to check with the homeowner if they have warranty information from the installer and to make sure the roof was installed by a reputable company.

As with any roof, regular seasonal monitoring in the attic space for signs of wet sheathing, and on top of the roof for early wear, and looking for granular loss and shingle gaps widening should be conducted. These will indicate that the roof is at the end of its life, and a homeowner should contact a reputable roofing contractor for review and replacement if necessary