Roof Slope For Snow

For warm roofs c t 1 0 as determined from table e 3 with an unobstructed slippery surface that will allow snow to slide off the eaves the roof slope factor c s shall be determined using the dashed line in fig.

Roof slope for snow.

You can enter this value either as a ratio x 12 or as an angle whichever suits you better. They then have the option of putting dormers on the roof without damage to the valleys penetrations lower roofs and property below due to sliding snow and ice. The steeper the pitch the better the snow will fall to the ground. This allows the snow to stay on while venting the roof system.

Roof slopes lower than 4 12 tend to perform well with metal roofs which are less prone to leakage and ice dam formation. E 2a provided that for nonventilated warm roofs their thermal resistance r value equals or exceeds 30 ft 2 h f btu 5 3 c m 2 w and for warm ventilated roofs their r value equals or exceeds 20 ft 2 h f btu 3 5 cm 2 w. If your roof is pitched enter the length and width of the flat area covered by the roof. In country with heavy snow and tough winter days the metal roof minimum slope is recommended to be 1 12.

Intuitively this is the number of inches of snow on your roof in the place where the cover is the thickest. There are some opinions that standing seam metal roof minimum slope is 12 but it increases the possibility of leaking on the few first days of snow arrival. On roof slopes between 4 12 and 6 12 rough textured roofing materials work best. At these slopes snow creeps rather than slides and is easy to manage.