The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.
Minimum slope for tile roof.
However with modern roofing materials such as boral roofing tiles the minimum roof pitch can be as low as 15.
However on extremely steep roofs above 19 12 or on vertical applications wind currents may cause tiles to rattle.
In general there is no maximum slope for tile roofs.
Asphalt shingles continue to be the most widely installed roof covering option in north america.
In traditional home construction it was not recommended to have a roof pitch lower than 20.
Although the minimum roof pitch for residential homes may vary depending on city and state building codes.
Clay tiles are colorfast which means their tints improve rather than fade over time.
For asphalt shingle clay and concrete tile metal shingle slate and wood shake and shingle roof systems nrca recommends slopes of 4 12 or more.
Both clay and concrete tile are available in many colors and are naturally weather resistant.
To avoid this use wind clips on each tile along with a construction grade silicone sealant or other approved sealant.
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.
The minimum roof slope allowed by code for any type of roofis in 12 applicable only to coal tar pitch roof systems.
According to this code the minimum slope for asphalt shingles is 17 degrees or two vertical units to twelve units in the horizontal.
The irc recommends a minimum pitch of 2 5 12 for these materials.
Sunday july 1 2018 the international residential code irc specifies a minimum 4 12 pitch 4 inches of vertical rise for every 12 inches of horizontal run for a clay or concrete tile roof except that a pitch as low as 2 1 2 12 is allowed when two layers of underlayment are applied.
The requirements for an asphalt shingles roof are contained in the international building code.
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.
Minimum roof slope roof pitch r905 3 2 clay and concrete roof tiles can only be installed on roof slopes of 2 1 2 12 or greater.
The following tableprovides the minimum required allowable roof slope for each type of roofing material mentioned in the code.