How to Use a Roof Truss Calculator

Posted on May 18, 2022 in Roof Inspection

Roof Truss Calculator
Trusses are structural pieces that form both sides of a roof’s pitch and span the space between the walls. Rafters are the boards that form the two sides that angle upward and connect at the peak. Trusses are normally purchased as pre-assembled units that include the rafter structural element. Knowing how to use a roof truss calculator gives you a fast way to estimate truss dimensions. The calculator produces the rafter length and the number of trusses needed based on roof size.


Common Roof Structure Terms

When learning how to use a roof truss calculator, it’s helpful to know the mathematics within it. The structural elements of a pitched roof contain pieces composed of right triangles. The Pythagorean theorem allows you to figure out the length of one side of a right triangle if you know the lengths of the other two sides. This is expressed in the equation A squared + B squared = C squared. To use the calculator, you’ll be gathering dimensions related to the roof.

  • Span – Distance between the walls beneath the eaves of the roof.
  • Roof rise – Distance from the top of the wall to the peak of the roof.
  • Roof run – Horizontal distance from the outer wall to the middle point beneath the roof’s ridge.
  • Roof pitch – The angle of the roof’s slope.
  • Roof length – The horizontal distance between both outer edges of the roof.
  • On center spacing – The distance from the middle of the truss to the middle of the adjoining truss.

Roof Truss Calculator

How To Use A Roof Truss Calculator

  1. Measure the rise of the roof.
  2. Measure the run of the roof.
  3. Enter the rise dimension into the calculator.
  4. Enter the run dimension into the calculator.
  5. The calculator will produce the rafter length.
  6. Alternatively, you can enter the pitch of the roof instead of the rise.
  7. Use a roof pitch calculator to get the pitch/angle of the roof.
  8. Enter the pitch and run figures into the calculator to receive rafter length.
  9. Overall, as long as you know any two dimensions, a roof truss calculator can use them to find the third dimension.
  10. In addition to rafter length, you also need to know how many trusses are needed.
  11. To calculate truss count, you need to measure roof length.
  12. Next, find the on center spacing specified in the building plans.
  13. Enter the roof length and on center spacing figures into the calculator.
  14. The calculator will produce the number of trusses needed for the roof.
  15. A roof truss calculator may also figure the approximate cost for you.
  16. If you know the price of one truss, enter the figure.
  17. The tool will multiply the individual cost by total truss count to let you know the cost of materials.
  18. If you know labor costs, you may enter that value as well.
  19. After entering individual truss cost and labor cost, you will see the estimated total cost.

Accurate Roof Repair and Replacement

No one can afford to make any mistakes on a roof. A sound roof is vital for protecting the entire structure from the elements. If you need structural roof repair, roof replacement, or are building one from scratch, talk to PJ Fitzpatrick. Roofing has been the core of our service offerings for decades. Call us at 1-877-246-4354 for a roofing estimate today.

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