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Cutting Common Rafters

The values on the calculator that we use for common roof framing are: Pitch, Rise, Run, and Diagonal. If you have any two of those values, the calculator will quickly figure out the rest of the right triangle—which means it will tell you everything else you need to know about a rafter.

Most of the time, the two values I have are the run of a building and a specified pitch, which is why I used these values for the example in this online tutorial:

Comments/Discussion

8 Responses to “Cutting Common Rafters”

  1. Jeff

    Excellent video and explanations. The only downside I think is that you need to show how to do it in long hand without the calculator and be very specific. Then I think you have a complete first rate tutorial that everyone will want to see. Good job!
    Please never publish my email address

    Reply
  2. Bill Gesell

    Mike,
    After reviewing numerous articles and books, your tutorial on cutting common rafters is the best I have seen. I do not do 2 story garages everyday so now I am confident I can make 16:12 2×10 rafters fit…With one exception: In testing your method on a shorter board and using a Construction Master Pro all the calculations run, calculated rise, pitch, diagonal, plumb cuts/lines worked fine but when I added the HAP and deducted the 11.25″ ridge beam, my story pole was 5/16″ higher than it should be. Can you tell where I may have erred or is 5/16″ manageable? Thanks.

    Reply
  3. Emanuel Silva

    Mike,
    Great video. Very easy to follow and understand.
    Thanks again

    Reply
  4. Gigi Tirlea

    Mike,
    What a great video about “Cutting Jacks rafters” like this one about “Cutting Common Rafters”.
    Thanks.

    PS
    I am in Europa, Romania, and i use a framing square in millimeters by Stanley.

    Reply
  5. Michael P Sloggatt Sr

    Sorry Bill – I just saw this –
    5/16″ is a manageable error, I typically drop 1/4″ off my ridge post because the discrepancy is so common. Question is Why? —
    Lumber – Never perfectly straight , Never exact thickness, Hap, due to variance in width of board ( due to Moisture content, Mill etc .) I ‘d rather be 1/4″ shy & shim it up to fit ..
    Mike

    Reply

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