1 12 Roof Slopes

The table below shows common roof pitches and the equivalent grade degrees and radians for each.

1 12 roof slopes.

Most roof s have a pitch in the 4 12 to 9 12 range. This means for every 12 horizontal units the roof must rise a minimum of two and one half vertical units. Arctan 3 12 14 0 the primary purpose of pitching a roof is to redirect water and snow. I e 4 inches of rise per 12 inches one foot of run.

Metal roof panels should be installed on roof slopes according to particular seams 2015 irc r905 10 2. Slopes greater than 18 12 are found on a frame roofs and some mansard style. The picture below shows the pitch of a 7 12 roof slope meaning that for 12 of horizontal measurement roof run the vertical measurement roof rise is 7. Built up roofs should be installed on roof slopes 0 25 12 or greater 2015 irc r905 9 1 except for coal tar built up roofs that have a minimum roof slope of one eighth unit vertical in 12 units horizontal 1 slope.

If asphalt shingles are to be installed on a low slope roof special steps are required to avoid short roof life and roof leaks. Clay and concrete roof tiles can only be installed on roof slopes of 2 1 2 12 or greater. Simply locate a roof rafter board place the end of the level against the bottom edge and measure from the 12 inch mark vertically to the bottom edge of the rafter. Using a tape measure make a pencil mark 12 inches from the end of a carpenter s level.

1 12 roof pitch angle 4 76 degrees. This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement. The exact roof slope in degrees is given by the arctangent. Then you ll be able to measure slope from an unfinished attic space under the roof.

What exactly is roof slope. Some sources consider low slope to include 3 12 pitch roofs. If a roof rises 1 in a length of 12 this is 1 12 roof pitch. Roof slopes are most commonly defined by the rise over run ratio.

Thus pitch is typically greater in areas of high rain or snowfall. In degrees 10 2 in 12 or 1 in 6 is considered a minimum. Low slope roofs are from 0 to 3 12 in pitch. A pitch over 9 12 is considered a steep slope roof between 2 12 and 4 12 is considered a low slope roof and less than 2 12 is considered a flat roof.

If a roof slope rises say 4 inches when measured 12 inches along the bottom of a horizontal roof truss the roof slope is said to be 4 12.