Montana Roof Pitch Requirements

Roofs between 2 12 to 4 12 pitch can use standard asphalt shingles but must have two layers of underlayment installed in the following manner.

Montana roof pitch requirements.

Clay and concrete roof tiles can only be installed on roof slopes of 2 1 2 12 or greater. Anything above that will require you to put out higher cost because they are already considered as higher pitch. Class a b or c roofing shall be installed in areas designated by law as requiring their use or when the edge of the roof is less than 3 feet 914 mm from a lot line. Minimum roof slope roof pitch r905 3 2.

In areas of the state outside of certified city county and town jurisdictions the design snow load shall be based on the ground snow loads developed in snow loads for structural design. But since there is still a wide variety of slate roofing systems there are occasions when the minimum pitch can go down to as low as 15 0 depending on the uniqueness of the roof. The minimum pitch is typically 3 12 meaning the roof should rise 3 inches for every 12 inches of horizontal foot. Montana ground snow load finder.

Low slope roofing products must be used. Local and or state requirements on the ground snow loads or the roof loads subsequently calculated from these values supercede the values provided by this snow load finder tool. Snow loads shall be determined by the building official. Roofs shall be covered with materials as set forth in sections r904 and r905.

The standard of lower pitch actually ranges between 1 12 to 5 12. Roofs less than 2 12 pitch cannot use standard asphalt shingles. This means for every 12 horizontal units the roof must rise a minimum of two and one half vertical units. Note that the state of montana requires a minimum roof snow load of 30 psf be used for design.

Built up roofs shall have a design slope of a minimum of one fourth unit vertical in 12 units horizontal 2 percent slope for drainage except for coal tar built up roofs that shall have a design slope of a minimum one eighth unit vertical in 12 units horizontal 1 percent slope. With regards to the pitch the building standard code bs 5534 recommends a minimum pitch of 200 for slate roofs.