Using A Speed Square To Determine Roof Pitch

Constructing a new shed roof at the desired pitch is as easy as knowing how to use a speed square.

Using a speed square to determine roof pitch.

If a magazine such as finehomebuilding is going to put out an article to teach a topic it should use the proper words and definitions. While it is possible to estimate the amount of necessary materials using only the total roof area measurement as can be seen from the table depending how large the pitch of the roof the actual area of the roof can differ by up to 2 236 from the measured total area at a pitch of 24 12. A speed square and level can be used to easily find the pitch of a roof. The speed square also called a rafter angle or triangle square is an extremely versatile tool originally intended to help carpenters quickly and accurately mark roof rafters it is a triangle shaped measuring tool that s invaluable for the diyer s tool box.

Swing the square until you read the desired angle on the board s edge and make your mark. What is a speed square. How to measure roof pitch with a speed square. Photo 2 shows how to use the speed square to mark a 33 1 2 degree angle the same as you would need on a rafter tail for a roof with an 8 12 pitch.

Made from plastic aluminum or steel this multi measuring tool combines a protractor a try square a ruler a. I hear read all too often this misuse and usually ignore it. Directly below the 6 inch mark on the framing square read the required rafter length 13 42 per foot of run for a 6 inch rise 6 in 12 roof. You can use the speed square to mark an angle such as when cutting a rafter tail by holding the pivot point against the board.

Therefore if your roof rises 4 inches over the course of 12 inches of horizontal run then your roof pitch is 4 12. Use a level and a pencil to make a plumb vertical line on one face of an existing rafter. As stated in the video speed squares have useful markings on them from 0 to 12. Set the level on the edge of the speed square as shown below then place the heel of the speed square on a rafter or gable edge of the roof.