Roof Slope For Snow

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.

Roof slope for snow. At these slopes snow creeps rather than slides and is easy to manage. Roof slopes lower than 4 12 tend to perform well with metal roofs which are less prone to leakage and ice dam formation. The slope that works best seems to be 5 12. On roof slopes between 4 12 and 6 12 rough textured roofing materials work best.

In country with heavy snow and tough winter days the metal roof minimum slope is recommended to be 1 12. This allows the snow to stay on while venting the roof system. If your roof is pitched enter the length and width of the flat area covered by the roof. 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.

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. 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.