Minimum Pitch For Roof Trusses

The minimum roof pitch is also subject to the standards set forth by the various building codes used in the respective regions.

Minimum pitch for roof trusses.

This table is considerably more useful that the one that was in the previous 1990 edition of the regulations as not only maximum truss spans are indicated but also the allowable and recommended pitch of the roof and the member sizes and grades of timber that are specified in sans 1783 2. Importance of a roof pitch. Flat the most economical flat truss for a roof is provided when the depth of the truss in inches is approximately equal to 7 of the span in inches. Note that roof pitch is sometimes used in parallel with roof slope.

However roof pitch is technically measured and defined differently. The rise will be the elevation change over the 12 inches. Difference in slope between the top and bottom chords is at least 3 12 or the bottom chord pitch is no more than half the top chord pitch. The run or the base number is 12 inches.

However you can only use this pitch with built up roofing or specialized synthetic roofing. This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement. For example a slope of 6 12 means for every 12 inches of horizontal distance the slope of the roof will rise 6 inches vertically. So if your roof rises 4 inches for every 12 inches of horizontal length then the pitch of your roof is expressed as 4 12.

I e 4 inches of rise per 12 inches one foot of run. Roof pitch is the measurement of roof steepness. The minimum roof pitch for shedding snow is around 30 or a 6 12 or 7 12 slope although this is not a definite as the material of your roof the direction of the snow and wind are some factors that can affect whether or not snow will slide as roofs of as little as 10 have been reported to shed snow. The chief reason for having a roof pitch is to redirect water and snow away from the roof and avoid any percolation that might result from stagnation of water on the roof.

The way pitch also known as roof slope is measured is rise over run. The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run. 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. Pitch slope the pitch or slope is the incline of the roof expressed as a fraction describing the rise over the run.

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.