Roof Area Multiplier

For roof slopes expressed as x in 12 rise in run the roof pitch multiplier is determined by finding the square root of rise run 1.

Roof area multiplier.

The roof pitch multiplier is responsible for giving an accurate pitch measurement of the roof. Determine how many square feet of roof area a building has by measuring blueprints or plans. That gives you 5 590 square feet which is the actual area of the surface of the roof. 8 inches and you have an 8 in 12 pitch.

This roof pitch chart will give you your multiplier. For multi pitched roofs simply add the areas of all common pitches together by toggling layer visibility from the summed layer identified by the eye symbol at the left of the layers control. Determine how many square feet of roof area a building has by measuring from the ground. Or just enter your numbers into this roof pitch degrees.

If this distance measures 4 inches you have a 4 in 12 pitch. Take the area of the roof s footprint say it s 5 000 square feet and multiply 5 000 by 1 118. And for a roof with a slope of 6 12 that number 1 118 is your roof slope multiplier. On a ladder beside the roof place the level a foot or so up the roof hold it level and measure from the 12 inch mark on the level s bottom straight down to the roof.

And that s the number you were looking for. Take your area result and multiply it by the pitch multiplier or slope correction factor found in the table above to arrive at the roof s surface area.