The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.
Shingle roof slope.
The 2 12 number is rise over run or two units of vertical for every 12 units horizontal.
The roof shingle calculator is a free estimator that serves a useful purpose during any roof repair or replacement project.
They provide excellent weather resistance great value and now more than ever a tremendous range of beautiful designs and color blends.
The roof pitch between 2 12 and 4 12 is considered as a low pitch roof so shingles can be installed in the roof slope between 2 12 and 4 12.
Shingles of all types need to have a slope to function properly.
That works out to about nine degrees if that works better for you.
Once you enter the basic roof dimensions and enter the type of roof you will get a very accurate result telling you exactly the amount of shingles that are required to cover your new roof.
Considering the roof slope requirement is important.
Why is 2 12 the minimum.
This means for every 12 horizontal units the roof must rise a minimum of 3 vertical units.
Asphalt shingles continue to be the most widely installed roof covering option in north america.
The following table provides the minimum required allowable roof slope for each type of roofing material mentioned in the code.
Metal roof shingles can only be installed on roof slopes of 3 12 or greater 25 slope.
The minimum requirement is 2 12.