Steep Slope vs Low Slope Roofing


There are two main categories of roofing products: Steep, and low slope. The slope of a roof is determined by its rise and run, the run always being 12”. Anything under a 3/12 pitch is considered “low slope”. All low slope roofing products are waterproofers, while steep-slope products are water shedders.

Steep slope products are shingles or tiles that layer into each other, shedding water off each piece onto the next one. There needs to be a decent slope so the water doesn’t sit and travel up-slope between the layers of product.

Low slope products are divided into two categories of their own: rolled product and coatings.

Rolled products such as Modified Bitumen (asphalt/fiberglass) and TPO (polymer/fiberglass) are laid out onto decking or insulation and welded or glued at the seams. Coatings are essentially painted layer by layer onto insulation or an existing roof.

Most residences are steep slope, but often times additions or patios will require low slope roofing products. Modified Bitumen is typically used on homes for low slope needs and works best on slopes of 1/12-3/12. The bitumen is asphalt based and has a similar life expectancy as the asphalt shingles. However, the seams on a Bitumen roof break much easier than TPO. TPO is widely used on commercial buildings and dead flat structures (0/12) and will last nearly twice as long as Modified Bitumen.

At Arrington Roofing we specialize in steep and low slope roofing, and we proudly blend the two when necessary. If you have a low slope section of your roof that needs replacing give us a call to see if Modified Bitumen or TPO is right for you.

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