As well a slope of 4 12 is most commonly considered the lowest slope for standard shingle installations.
Low slope roof shingles.
Low slope roofs present a challenge where water is concerned.
Some will argue that shingles shouldn t be used for low pitch roofs at all.
If you have a low slope roof but would love to have a shingled look rather than other solutions like rolled sheet roofing you are in luck.
And by the way the manufacturers instructions i reviewed for the shingles i was interested in buying described installations down to a 2 12 pitch.
A 3 per foot slope is considered low but may be acceptable if a double layer of felt is used.
However those naysayers would be wrong.
They typically had different underlayment recommendations for low slope roofs 2 12 to 4 12 pitches but that was about it.
3 tab shingles versus laminated shingles for low slope roof.
Low slope roofing shingles.
This low slope application requires a double layer of 15 felt underlayment cemented together for a distance extending from the eaves up to a point 24 inches inside the interior wall line of the building.
The usual slope for asphalt shingles is a 4 or greater rise for every horizontal foot of run.
Cover the entire low sloped roof area with a self adhered modified bituminous membrane that will act as an ice and water.
The acceptable underlayment installation options for low slopes are described in the canadian standards association asphalt shingle application standard csa a123 51 as follows.