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.

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

Line up the pivot point on the bottom edge of the rafter. Place the pivot point against the shingles. 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. Step 3 note the number on the common scale parallel with the 45 degree angle of the square.

As an example pivot the speed square until the numeral 30 aligns with the opposite edge of the piece of material. Follow the bottom edge of the rafter to where it meets the common pitch reading. Read the pitch on the side of the rafter square. Use a spirit level to mark a straight vertical line across the rafter.

Hold the pivot point against the board and move the square until your desired angle lines up with the edge of the board. It s often marked right on the tool. With a torpedo level and a speed square you can pretty accurately gauge the pitch of any roof with a gable end photo 1. Then place a torpedo level on the fat base of the rafter square and adjust the square until the level is level.

If not the 0 degree mark should be at the opposite. At the corner of the square there is a pivot point. This is called the plumb line. Align the lip of the rafter angle square along the plumb line.

The pivot is a point at one end of the lip about which you can rotate the speed square to find angles. Draw a line down the pivot point edge of the speed square on the exact same side that the 90 degree line was drawn. Because the speed square is a 90 degree angle each line on the diagonal represents one degree for a total of 90. Now that the square has been lined up on the 30 degree mark however the angle drawn will be a 30 degree angle.