Roof Slope Conversion Factor

The roof pitch factor is also used to calculate the length of common rafters.

Roof slope conversion factor. In that case the multiplier is multiplied by the run of the rafter the horizontal distance that will be covered by the rafter. Use the following formula which also describes a right triangle. A roof pitch of 4 in 12 4 12 has a rise of 4 and a run of 12. The total run is the distance from the peak to the edge of the roof which in this case is the total width divided in half which is equal to 10 feet or 120 inches.

The slope of the roof provides the rise and the run to be plugged into the equation. For example if you measure 4 inches the pitch of your roof is 4 12. The headache of using pythagoras and trigonometry can be spared by making use of these charts. See below after the table for directions on how to convert any roof slope from one form to another even roof slopes not shown in the table.

Two most common methods 4 12 or 4 12 are used for marking the pitch of a roof. Usually they come in the form of a roof pitch diagram chart but other times it will be presented to you in a conversion format. It s just a little math. 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.

Charts list the slope factor for various pitches usually from 1 12 to 12 12. Since pitch is the rise over a 12 inch run divide the run by 12 to get the multiplier in this case 120 12 10. You can also calculate roof pitch even without using a roof slope calculator. Multiply the roof length by the gable wall length 40 24 960.

Here are the equations you may use to solve for the length of the slope and the rafter. On blue prints architects engineers usually display the pitch of a roof in the format shown on the image where number 4 represents a rise and number 12 represents a length. The area of this roof 1073 3 sq. The following table shows how the same common roof slopes can be expressed using rise in run ratios degrees and percentages.

Also see our page quick reference. The area of a hip roof equals the area of a gable roof with the same dimensions. Multiply this amount by the slope factor 960 1 1180 1073 28. In essence a roof pitch chart is provided as a rough guide usually by a roofing company to help you see what the average roof pitches tend to be.

Degrees to roof pitch rise in run to see a table. The roof slope factor chart also consists of conversion factors to determine the slope of the roof. For instance the ever last roofing company distributes a chart to the general public. A 10 slope roof should not be confused with a 10 pitch roof as a 10 slope roof means that the roof rises by ten inches for every foot of run.

You could calculate the slope factor for every single roof pitch but as a public service many roofing companies provide slope factor charts.