How to Measure Rolled Roofing

Position a ladder next to the roof you are covering and climb up onto it to access the roof. Always wear nonskid work shoes when working on any roof.

Climb to the top of the roof if it has a slope or walk to the middle of one of the longest sides if the roof you are measuring is flat. Place the tape measure on the peak of the roof, or the edge, and have another person stretch it down to the bottom of the slope or to the other side for flat roofs. Note the measurement, which is the slope or width of the roof.

Walk to one side of the roof and place the tape measure at the edge of it. Hold it firmly while the other person stretches it across to the other side, which determines that length of the roof.

Multiply the two numbers together to arrive at the total square footage of rolled roofing you require to cover a flat roof. If you have a sloped roof, multiply the slope number by two to account for the other side of the roof. Then multiply that number by the length of the roof to arrive at the amount of rolled roofing required to cover both sides.

Add 1 inch to all measurements to allow for a ½-inch overhang at the sides of the rolled roofing.

Measure the width of your rolled roofing or refer to the package measurements. Divide the total roof slope by the width of the roll to see how many rows of material you will install. Add 3 inches to each row to allow for overlap, which prevents leaks.