Use a level against the underside of the rafter you re measuring to get the most accurate value.
How to measure a triangle roof.
If you have a roof section that s 30 feet 9 1 m long and 12 feet 3 7 m high multiplying those dimensions would give you an area of 180 square feet 17 m 2.
On a ladder beside the roof place the level a foot or so up the roof hold it level and measure from the 12 inch mark on the level s bottom straight down to the roof.
8 inches and you have an 8 in 12 pitch.
Access one of the rafters then take the measurement this way.
L 30 feet h 12 feet 30 12 2 180 square feet.
So if you divide your answer of a product of length times height by two you will get the area of a triangle.
Locate the level s 12 inch mark.
For trapezoidal roofs measure the bottom edge the top edge also known as the ridge and the distance between the 2 edges.
The length l times the height h of a triangle is twice its area a2.
If the roof has a triangular shape stretch your tape measure along the bottom edge then measure from the peak point down to the center of the bottom edge.
Determine the distance from the edge of the roof to a point on the same plane directly under the highest point.
For example if the roof slopes up from the front of a.
If this distance measures 4 inches you have a 4 in 12 pitch.
Record this as the roof width.
Pitch measurement method 1 1.
The basic formula for finding the area of a triangle is the base times the height in this case the distance between the base and the peak.