Low Pitch Roofing Underlayment For Shingles

The acceptable underlayment installation options for low slopes are described in the canadian standards association asphalt shingle application standard csa a123 51 as follows.

Low pitch roofing underlayment for shingles.

Asphalt shingles can be used on roofs with a slope of 2 12 to 4 12 if double coverage underlayment is used. Then apply standard asphalt shingles over the membrane. Because of the non absorbent nature of asphalt the shingles themselves provide an element of waterproofing which is why they work well for low slopes. Asphalt saturated felt along the eaves and lap succeeding courses by 19 inches as shown in figure 2 3.

When combined with the proper underlayment materials and application they are an excellent solution for a low slope roof with a pitch between 2 12 to 4 12. As well a slope of 4 12 is most commonly considered the lowest slope for standard shingle installations. 1 cover the entire surface with a self adhesive flashing membrane such as grace ice water shield there are many equivalent products. Cover the entire low sloped roof area with a self adhered modified bituminous membrane that will act as an ice and water.

For starters the textured underlayment isn t just weatherproof. The membrane will outlast the shingles and seal around all nail penetrations. For a low slope residential roof there are two main options. Most manufacturer and industry recommendations require or at the very least recommend special underlayment or other considerations on roofs between 2 12 and 4 12.

Despite its wide range of compatibility it still does offer a bit more whenever you re dealing with asphalt shingles.