How to Figure a Roof Span

The span of your roof is the horizontal distance between the two walls that support it. Knowing the span of your roof is important if you plan to carry out any structural work on it or if you want to calculate the entire area of the top of your building. The shape and design of your roof has no bearing on its span, so you can use the same method to measure it whether you have a shed roof, flat roof, gabled roof or gambrel roof.

Things You'll Need

• An assistant
• Tape measure
• Bubble level
• Pen and paper

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Instructions

1. • 1

     Ask your assistant to hold one end of a tape measure to the corner of the building you're measuring.

   • 2

     Pull the tape measure along the building's width to the other end.

   • 3

     Use a bubble level to make sure your tape measure if level. If you're measuring at an angle, the reading you get will be inaccurate.

   • 4

     Note the width of your wall. This is the span of your roof.