Snow can certainly slide off of a 4 12 roof.
Propper roof pitch for snow.
Slopes greater than 6 12 will tend to shed snow regardless of the texture of the material on them so roof slopes should be configured to avoid shedding anywhere people might be walking or exiting.
Although there is no single standard roof pitch used on all sloped roofs factors such as roofing materials and local climate help to determine the appropriate range of pitches for a given building.
Roof pitch is a measurement of a roof s slope expressed as a ratio.
This will extend the life of your roof.
A 1 4 inch slope may work in alabama but one can expect leaks in minnesota or.
Even in these arid regions so called flat roofs are still installed with a slight pitch to keep water from pooling on top of the structure.
Therefore attic space can be at a premium with a low pitch roof.
The higher the roof pitch the more often the snow slides off.
Others allow a 1 4 inch slope.
The minimum roof pitch is also subject to the standards set forth by the various building codes used in the respective regions.
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.
Importance of a roof pitch.
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.
In snow country i want a 9 12 minimum and a 12 12 is preferable.
This has more to do with weather conditions than pitch.
High pitch roof pros.
Flat roofs are common with industrial buildings boasting wide roof spans and are also popular in dry climates for houses where there is no need for the roof to help disperse rain and snow.
The chief reason for having a roof pitch is to redirect water and snow away from the roof and avoid any percolation that might result from stagnation of water on the roof.
Metal roofs leak under these circumstances.
If you are building a new roof however consider the climate to determine the correct pitch and proper materials.
Some metal building manufacturers will not warranty a roof with a 1 4 inch slope.
When the snow piled up on the roof melting occurred and ice dams resulted in water ponding 3 inches deep.
Cheaper by far than a full roof of ice and water shield and that goes back to my comments about roof pitch.
We use full ice and water shield protection in low pitch roofs 5 12 and under.
Since the pitch of the roof is lower it can act as a catch all for tree limbs and other debris.
However the larger factor is that when the sun comes out radiant heat passes through the snow is reflected outward melts the snow from underneath and causes it to slide.
Care must be given so that debris does not collect and thus cause damage.
