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.
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.
1 cover the entire surface with a self adhesive flashing membrane such as grace ice water shield there are many equivalent products.
Start with a 19 inch strip of 15 lb.
For a low slope residential roof there are two main options.
Asphalt saturated felt along the eaves and lap succeeding courses by 19 inches as shown in figure 2 3.
Despite its wide range of compatibility it still does offer a bit more whenever you re dealing with asphalt shingles.
For starters the textured underlayment isn t just weatherproof.
As well a slope of 4 12 is most commonly considered the lowest slope for standard shingle installations.
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.
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.
The acceptable underlayment installation options for low slopes are described in the canadian standards association asphalt shingle application standard csa a123 51 as follows.
Product overview if you re looking for the best roof underlayment for asphalt shingles then the tyvek protec 120 should be on your wishlist.
The membrane will outlast the shingles and seal around all nail penetrations.