Wind exposure of roof.
Roof angle for snow.
The density of snow depends on whether it s fresh wet wind packed or mixed with ice.
Importance occupancy and use of the building.
Pitch angle incline slope they all can be used to refer to the steepness of a roof.
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.
For slopes below 20 degrees systems such as epdm fibreglass metal roofing can be used.
For lots more information on which roof finish to use for which slope and indicative costs.
If you re not sure which type to choose always settle for the wetter types as they are denser.
Visit the shed roofing page.
The purpose of pitching a roof is to enable water and snow to run off so the greater the amount of rain and or snow an area receives the greater the amount of pitch needed for the roof.
In general determining the pitch of an existing roof is a simple calculation.
Intuitively this is the number of inches of snow on your roof in the place where the cover is the thickest.
In snowy areas your roof should be at least 10 12 40 to allow snow to shed while the safest roof pitch in very windy areas is between 4 12 6 12 18 5 26 5.
This can be accomplished by measuring the number of inches the roof rises vertically for every 12 inches it extends horizontally.
You can enter this value either as a ratio x 12 or as an angle whichever suits you better.
In the roofing trade the go to term is pitch and it is expressed in terms of 12 inches so the pitch of a roof is determined by how many inches the slope rises for every 12 inches it runs horizontally.
The requirements for an asphalt shingles roof are contained in the international building code.
This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.
On multiple factors including.
Ground snow load value.
According to this code the minimum slope for asphalt shingles is 17 degrees or two vertical units to twelve units in the horizontal.
Roof snow load is defined as the weight of snow on the roof surface used in design of the building structure ibc 2012.
If water does not properly run off of a roof it will begin to seep in causing rot interior damage and possibly dangerous black mold.
