Using A Speed Square To Determine Roof Pitch

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.

Using a speed square to determine roof pitch.

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. 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. Place the pivot point on the square against the bottom of the rafter and align the 90 degree angle side of the square with the pencil mark. 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.

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. I hear read all too often this misuse and usually ignore it. A speed square and level can be used to easily find the pitch of a roof. Therefore if your roof rises 4 inches over the course of 12 inches of horizontal run then your roof pitch is 4 12.

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. Swing the square until you read the desired angle on the board s edge and make your mark. As stated in the video speed squares have useful markings on them from 0 to 12. To calculate the required rafter length multiply the total run length half the building width plus the width that the roof is to overhang the house wall by this number 13 42.

What is a speed square. Made from plastic aluminum or steel this multi measuring tool combines a protractor a try square a ruler a. A roof slope of 4 12 is a 1 6 pitch a 6 12 slope is a 1 4 pitch an 8 12 slope is a 1 3 pitch and so on. How to measure roof pitch with a speed square.