For example a roof that rises 3 inches for every 12 inches has a pitch of 3 12.
Slope roof tile regulations.
If the roof is close to a boundary which is often the case the roof should also have properties to limit the risk from fire spreading across the boundary.
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.
However on extremely steep roofs above 19 12 or on vertical applications wind currents may cause tiles to rattle.
Clay and concrete roof tiles can only be installed on roof slopes of 2 1 2 12 or greater.
Not all roofs need to be ventilated.
On slopes less than 3 1 2 12 roofing tile is considered decorative only.
California roofing laws cover everything from licensure of the roofing company to the types of shingles that must be used to the slope of the roof.
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.
This means for every 12 horizontal units the roof must rise a minimum of two and one half vertical units.
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.
Ventilation is not required to a warm roof system which is where the insulation is placed above the joists or rafters.
According to this code the minimum slope for asphalt shingles is 17 degrees or two vertical units to twelve units in the horizontal.
The underlying roof provides all the necessary waterproofing.
To qualify as a cool roof under the ladwp consumer rebate program the roofing material must have crrc 3 year sri value 75 for low slope 2 12 or 16 for steep slope 2 12 roofs for the enhanced rebate have crrc 3 year sri value 85 for low slope 2 12 or 35 for steep slope 2 12 roofs how to apply.
In general there is no maximum slope for tile roofs.
Nrca s recommended minimum roof slope guidelines for steep slope roof systems generally are greater at steeper inclines than those in the building code.
With a pitched roof the type of tile or slate you wish to use will be partly governed by how steep or shallow the slope is.
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 requirements for an asphalt shingles roof are contained in the international building code.
