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

Line up the pivot point on the bottom edge of the rafter.

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

As an example pivot the speed square until the numeral 30 aligns with the opposite edge of the piece of material. Because the speed square is a 90 degree angle each line on the diagonal represents one degree for a total of 90. Use a spirit level to mark a straight vertical line across the rafter. This is called the plumb line.

Now that the square has been lined up on the 30 degree mark however the angle drawn will be a 30 degree angle. Follow the bottom edge of the rafter to where it meets the common pitch reading. Align the lip of the rafter angle square along the plumb line. Place the pivot point against the shingles.

Then place a torpedo level on the fat base of the rafter square and adjust the square until the level is level. Step 3 note the number on the common scale parallel with the 45 degree angle of the square. 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. Hold the pivot point against the board and move the square until your desired angle lines up with the edge of the board.

Read the pitch on the side of the rafter square. Step 2 find an angle. If not the 0 degree mark should be at the opposite. 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.

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. The pivot is a point at one end of the lip about which you can rotate the speed square to find angles. At the corner of the square there is a pivot point.