How to Determine a House's Roof Pitch

Roof Method

• 1

  Lay a level on a flat surface. Hold the end of a tape measure on the left edge of the level and measure 12 inches to the right. Mark the 12-inch spot with a pencil or a black marker.

• 2

  Lean a ladder against the gable-side of your house. This is the side where the roof line meeting the house itself forms a triangle. Because you must measure a 12-inch strip of the sloped roof, use a ladder tall enough to safely reach the surface of the roof without standing on either of the ladder’s top two rungs.

• 3

  Hold the unmarked end of the level horizontally against the roof. Adjust the level until the bubble inside the level rests evenly between the two lines.

• 4

  Place the end of the tape measure on the roof and measure up to the line you made on the level in Step 1. This is your roof pitch. For example, if the measuring tape reads 6 inches, your roof pitch is 6-in-12.

Attic Method

• 5

  Lay a level on a flat surface. Hold the end of a tape measure on the left edge of the level and measure 12 inches to the right. Mark the 12-inch spot with a pencil or a black marker.

• 6

  Hold the unmarked end of the level horizontally against a rafter on the ceiling of your attic. Adjust the level until the bubble inside the level rests evenly between the two lines.

• 7

  Place the end of the measuring tape on the rafter and measure down to the line on the level you made in Step 1. The resulting number is your roof's pitch. For example, if the measuring tape reads 4 inches, your roof pitch is 4-in-12.