How To Find Roof Pitch Using A Speed Square

Finding roof pitch isn t rocket science it s simple geometry.

How to find roof pitch using a speed square.

To find the pitch just place the pivot point against the shingles. 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. Let us show you how to accurately determine roof pitch using simple tools level and measuring. 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.

You can also use a speed square to find level if you re on the job without a spirit level. If you need to find the pitch of an existing roof all you need is a level and a tape measure. A speed square will have two specialty protractor angle guides on the inside of the tool which has both common rafter angles and hip valley angles marked out. Use a level and a pencil to make a plumb vertical line on one face of an existing rafter.

Place the level horizontally along the rafter until it contacts the roof sheathing avoiding any protruding roof nails. Swing the square until you read the desired angle on the board s edge and make your mark. As a matter of fact finding the pitch of a roof was the motivating factor for how this tool was invented in the first place hence it s official name the rafter square. 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.

You can use a speed square to find pitches. You have a perfect 45 degree angle for easy corners. Simply brace the lipped side of the speed square against the edge of your board pencil a line up the hypotenuse of the speed square and voilà. Working from the interior side of the roof you ll need access to a roof rafter to measure the pitch.