It is uncommon to find a roof below 15 but for those very low pitch applications there are interlocking clay pantiles available suitable for use down to 12 5.
Minimum angle for pitched roof.
Divide the first part of the ratio by 12 to work out the pitch.
Pitched roofs can also be used to incorporate roof lights angled in a specific direction or dormer windows artists commonly use north facing roof lights to allow cool light into their studios.
Traditionally a minimum roof pitch of 20 was recommended in bs 5534 but modern tiles and slates have now been designed for applications as low as 15.
But since there is still a wide variety of slate roofing systems there are occasions when the minimum pitch can go down to as low as 15 0 depending on the uniqueness of the roof.
Normal shingle installation is allowed for all roofs with a pitch of 4 12 and above.
To convert between american roofing ratios and pitch degrees follow these steps.
Normal roof slope for typical installation.
However you can only use this pitch with built up roofing or specialized synthetic roofing.
The loft space would be much larger with a roof pitch of 45 degrees.
The roof pitch calculator is a convenient online tool you can use to quickly assess the pitch of your roof to determine the length of rafters you need.
Find the inverse tangent of the pitch to find the angle in degrees.
The picture below shows the pitch of a 7 12 roof slope meaning that for 12 of horizontal measurement roof run the vertical measurement roof rise is 7.
A 12 12 pitch roof has a pitch angle of 45.
Minimum roof pitch for shingles.
Asphalt shingles continue to be the most widely installed roof covering option in north america.
For that reason flat roofs are limited to these types of covering materials.
Flat and nearly flat roofs a pitch of 1 in 12 or 2 in 12 cannot be covered with shingles or shakes of any material since there is not enough angle to combat the danger of blow off.
The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.
The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.
This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.
If 4 12 and above is normal and 2 12 is minimum what about properties with roofs in between the two such as a 3 12 pitched roof.