Montana Roof Pitch Requirements

Montana ground snow load finder.

Montana roof pitch requirements.

Roofs less than 2 12 pitch cannot use standard asphalt shingles. 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. The standard of lower pitch actually ranges between 1 12 to 5 12. The minimum pitch is typically 3 12 meaning the roof should rise 3 inches for every 12 inches of horizontal foot.

Roofs shall be covered with materials as set forth in sections r904 and r905. 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. 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. 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.

Anything above that will require you to put out higher cost because they are already considered as higher pitch. Minimum roof slope roof pitch r905 3 2. Apply a 19 inch strip of underlayment felt on top of the ice barrier parallel to. Snow loads shall be determined by the building official.

Note that the state of montana requires a minimum roof snow load of 30 psf be used for design. The state of montana requires a minimum roof snow load of 30 psf be used for design 2 this minimum value applies to the final roof snow load that is calculated after all coefficients have been applied and it may be revised when justified by a design professional to the satisfaction of the building official. Clay and concrete roof tiles can only be installed on roof slopes of 2 1 2 12 or greater. 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.

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. This means for every 12 horizontal units the roof must rise a minimum of two and one half vertical units.