How To Find The Angle Of A Roof With A Speed Square

Align the lip of the rafter angle square along the plumb line.

How to find the angle of a roof with a speed square.

The hash marks with corresponding numbers between 1 and 30 refer to the roof s rise angle. Read the pitch on the side of the rafter square. The pivot is a point at one end of the lip about which you can rotate the speed square to find angles. Because the speed square is a 90 degree angle each line on the diagonal represents one degree for a total of 90.

Then place a torpedo level on the fat base of the rafter square and adjust the square until the level is level. Use a spirit level to mark a straight vertical line across the rafter. Draw a line down the pivot point edge of the speed square on the exact same side that the 90 degree line was drawn. Follow the bottom edge of the rafter to where it meets the common pitch reading.

Now that the square has been lined up on the 30 degree mark however the angle drawn will be a 30 degree angle. At the corner of the square there is a pivot point. With a torpedo level and a speed square you can pretty accurately gauge the pitch of any roof with a gable end photo 1. It s often marked right on the tool.

This is called the plumb line. Place the pivot point against the shingles. Step 2 find an angle. 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.

As an example pivot the speed square until the numeral 30 aligns with the opposite edge of the piece of material. 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. Holding the level and speed square level locate the measurement on the speed square where it meets the bottom edge of the rafter to find the angle of the roof in degrees. If not the 0 degree mark should be at the opposite.