The 2 12 number is rise over run or two units of vertical for every 12 units horizontal.
Minimum roof angle for shingles.
For simplicity sake every degree of pitch is roughly 4 75 degrees.
The minimum pitch for shingles is 1 6 which is equivalent to 4 inches rise to 24 inches run.
The asphalt shingle manufactures recommend that you install asphalt shingles on a recommended minimum of 4 in 12 or greater however most manufactures will warrant their shingles down to a 2 in 12 pitch if the recommended installation method is used.
These are also the most common pitches for shed roofs.
The following table provides the minimum required allowable roof slope for each type of roofing material mentioned in the code.
The highest degree possible is a 45 degree roof which is a 12 12 pitch roof.
Shingles of all types need to have a slope to function properly.
The angle of a 2 12 pitch roof is roughly 9 46 degrees rounded to 9 5 in most cases.
What is the minimum slope for an asphalt shingle roof.
According to this code the minimum slope for asphalt shingles is 17 degrees or two vertical units to twelve units in the horizontal.
Asphalt shingles continue to be the most widely installed roof covering option in north america.
This means for every 12 horizontal units the roof must rise a minimum of 3 vertical units.
The standard for roof pitch is 4 12 though a 2 12 is completely fine for most structures.
Installation on roof slopes below a 2 in 12 pitch is not recommended at all.
A shingle roof like this north dallas garage in the photo above may have a failure no matter how good a job the installer did.
How roof pitch determines suitable roofing systems.
Determine the minimum slope of the roof based on the roofing material.
The minimum requirement is 2 12.
The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems.
That works out to about nine degrees if that works better for you.
Use a handy tool like snow load calculator to help you determine if your roof can handle the weight of snow based on its pitch.
Again the most important consideration is the weather.
Metal roof shingles minimum roof slope roof pitch r905 4 2.
The requirements for an asphalt shingles roof are contained in the international building code.
Metal roof shingles can only be installed on roof slopes of 3 12 or greater 25 slope.
The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.
