The 2 12 number is rise over run or two units of vertical for every 12 units horizontal.
Minimum roof pitch for architectural shingles.
Tuesday september 11 2018 manufacturers of asphalt shingles recommend a pitch of 4 12 or more but the absolute minimum pitch is 2 12.
You could also opt for a pvc flat roofing membrane.
The recommended minimum roof pitch for shingles is 2 12 or simply two units of vertical rise to every twelve units of horizontal span.
What is the minimum slope for an asphalt shingle roof the short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.
Asphalt shingles continue to be the most widely installed roof covering option in north america.
What slope is considered low slope for shingles.
Therefore the asphalt manufactures base their warranties around the minimum recommended pitch of 4 in 12.
For pitches of 2 5 12 up to 4 12 the roof requires double underlayment.
For low slopes as well as any other slope your local building department should be contacted.
A roof slope of 2 12 up to but not including 4 12 is considered as low in residential construction.
Asphalt shingles should never be applied to roof slopes below 2 12 2 of vertical rise for every 12 of horizontal run or 9 5.
What precautions need to be taken to install shingles on low slopes.
What is the minimum pitch slope of an asphalt shingle roof.
4 12 to 20 12 pitches.
Pitch is measured in inches of vertical rise of the roof over one foot 12 inches of horizontal run.
So a 4 12 pitch roof rises 4 inches for every 12 inches of horizontal run.
Asphalt shingles installed on a slope below the recommended roof pitch asphalt composition shingles are designed to be installed on roof slopes greater than a 4 in 12 pitch.
Additional underlayment protection with special application methods are required when asphalt shingles are installed on a low slope roof following the manufacturer s application instructions.
The minimum requirement is 2 12.
There are some standing seam metal roofing options available from atas and other manufacturers that can be installed on a roof with pitch of 1 12.
However you can only use this pitch with built up roofing or specialized synthetic roofing.
Slopes above 19 12 are not recommended since tiles on very steep roofs can rattle.
It is important for shingle roofs to function properly and one method of ensuring that this is achieved is to observe the pitch requirements for the shingles.
So you would need to pick the right option as most regular standing seam metal roofs will require a roof pitch of 2 12 or even 3 12 at a minimum.
