How To Find Roof Slope Factor

Using a tape measure make a pencil mark 12 inches from the end of a carpenter s level.

How to find roof slope factor.

The most precise way to find the roof s slope is by measuring it from the underside. A roof pitch multiplier also known as a roof pitch factor is a number that when multiplied by the area covered by a sloped roof gives the actual area of the roof. For any roof slope expressed as x in 12 rise in run the hip and valley factor is determined by finding the square root of rise run 2. The maths behind this number is that it is the square root of rise run 2 1.

To accurately calculate the area of your roof you must first determine its slope or pitch. The whole table of roof pitch and slope gives a conversion factor so as to obtain a numerical figure of the slope. Use the factor instead. Locate the level s 12 inch mark.

For example if the pitch of the roof is 6 then it is written as 6 12. You don t have to climb a ladder and place a tape measure on the ridge and measure down to the base to find the length of the roof. Write down the number of inches between the roof and the bottom of the level 12 inches from the roof s peak. 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.

Divide the rise by the run the run is 12. Thus a moderate 6 in 12 roof pitch means that the roof rises 6 inches vertically for every 12 horizontal inches it runs. Enter 6 into the calculator slope factor 1 1180 multiply the roof length by the gable wall length 40 24 960 multiply this amount by the slope factor 960 1 1180 1073 28 the area of this roof 1073 3 sq. A roof s pitch is determined by how much it rises vertically for every foot it runs horizontally.

Then you ll be able to measure slope from an unfinished attic space under the roof. Access one of the rafters then take the measurement this way. Use a level against the underside of the rafter you re measuring to get the most accurate value. One medium to describe the roof pitch is in 12 runs.

Measure from an exterior wall to an exterior wall and divide by two.