Minimum Roof Pitch For Snow Loads

There are some standing seam metal roofing options available from atas and other manufacturers that can be installed on a roof with pitch of 1 12.

Minimum roof pitch for snow loads.

A minimum slope of 1 inch per foot is recommended in snow country. The 1 4 inch per foot slope was not adequate. The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems. The standing seam metal roof on this ice hockey rink leaked like a sieve a few weeks after the first snow arrived.

Per local ordinance it is 20 psf with further statement that snow loads shall be determined per section 7 of asce 7 but the design roof load shall not be less than a uniform snow load of 25 psf. So you would need to pick the right option as most regular standing seam metal roofs will require a roof pitch of 2 12 or even 3 12 at a minimum. Per 2003 irc and 2003 ibc. To figure out the load on your roof take the depth of snow in feet and multiply it by the weight of a cubic foot of snow.

Flat roof snow loads p f the snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load. If the snow weighs 10 pounds per cubic foot and there are 1 5 feet on the roof each square foot of the roof is getting 15 pounds of pressure. 90 mph for both 2003 irc and 2003 ibc. The minimum roof pitch is also subject to the standards set forth by the various building codes used in the respective regions.

Importance of a roof pitch. If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow. For example a roof with a 6 inch 12 pitch is one where it rises 6 inches vertically for every 12 inches of the horizontal run. In our case let s assume that our structure has a flat roof roof slope 5.

In general determining the pitch of an existing roof is a simple calculation. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10. This can be accomplished by measuring the number of inches the roof rises vertically for every 12 inches it extends horizontally. The following table provides the minimum required allowable roof slope for each type of roofing material mentioned in the code.