How to Calculate Roof Plans

There are many steps involved in calculating roof plans. A roof must be designed and constructed properly for everything in your home to function correctly. The size of the roof and the type of roofing that will be used are the options you have to choose from when figuring your roof. No matter what type of roof you put up, it must be carefully designed and constructed before any building on it can take place.

Calculator
Roof pitch chart
Tape measure
Inclinometer

Instructions

- 1
  Inspect the trusses to verify that they have been installed and the roof is ready to be added. Measure the width and length of the roof to get the total square footage. Record the measurement of the length and width of each side. Multiply the length by the width of the first side and add it to the second to get this number.
- 2
  Determine the pitch of the roof. The pitch is the rise over the run. Set the inclinometer on the top ridge of the house and record the measurement of the slope. Take that measurement and use a roof pitch factor chart to figure out how much will need to be added to the total square footage. For an 8/12 pitch, multiply the total square footage by 1.2, and for a 7/12 pitch multiply it by 1.16.
- 3
  List all the materials that will be used on the roof and the type of roofing you will be installing. Add in ice and water guard, felt underlayment, drip edge to go around the perimeter, roofing shingles, starter strips and ridge vents.
- 4
  Add all of the totals together to get the price of the roofing materials. Add in the cost of roofing nails and a nailer if you do not already have those.

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