How To Make A Common Rafter For Any Width Structure

Picture of How To Make A Common Rafter For Any Width Structure

If any terms or wording I have used is confusing at all or anything seems unclear, please feel free to ask a question. I don't check everyday, but I do check in often, and would be happy to answer any questions or edit something that is unclear for you.....

These instructions should enable the moderately skilled handy-person to produce a set of common rafters for any building. These instructions are for the moderately skilled. I have omitted basic steps on the safe use of the tools needed. If you are unfamiliar with tools, and the dangers they possess these instructions are not for you.
Rafter stock will be determined by geographic location, the width of your building, and local building codes. . . .
A pencil, tape-measure, circular-saw, speed-square, framing square, and saw-horses.
Risk of serious injury or death is possible!
If you are unfamiliar with the listed tools and the dangers they possess, these instructions are not for you.
These instructions are formatted in such a way that the peak of the rafter should be to your left, the tail should be to your right, roof side away from you, ceiling side close, laying on the saw-horses. Please read the entire instructions before beginning and then follow them step by step.

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Step 1:

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(1) Divide the width of your building in half, and remember that number.
(If the building is 40 feet the working number is 20, if the building is 4 feet, the working number is 2.)

Step 2:

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(2) Establish the pitch you desire your roof to be. (If working on a large structure, check with local code enforcement before proceeding unless working from an approved set of blueprints.)

Step 3:

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(3) Find the Length Per Foot Run Common Rafters row on the framing square.

Awesome... very, very concise and helpful. Building a clerestory shed and the rafter template supplied with MIGHT have worked if the final dimensions where exactly as the plan suggests, but of course, the real thing varies by enough to make the template as useful as ashtrays on a motorcycle. Your explanation of the maths behind the calculations was perfect. Thanks a bunch.

Thank you so much for the feedback Steve. It's great to hear this is useful to folks out there in the web. Hope the shed turns out good for ya.


fjm514314 days ago

Hi, thanks for this article. You made the process so simple. Do you have instructions on how to make valley rafters?

Joesmania (author)  fjm51434 days ago

I signed in with Google+, and it gave me a different user name... JoeS3. I didn't realize it until I hit the "Make Comment" button. Needless to say, the reply back to you from JoeS3 was me.

Thanks again.


JoeS3 fjm51434 days ago

Thanks for your kind words fjm. I have wanted to do a piece on valleys and hips but spare time eludes me. I'm thinking I'll do future instructables in video, even repeat this one including an easy way for buildings with odd widths like 22' 7 & 3/4". In hind sight, I only give the mathematical process for foot increments.

It is on my list, and your interest may just be the motivator I needed.

Thanks again, J.

BIG - X1 year ago
Joesmania (author)  BIG - X1 year ago
Thanks for the feedback BIG - X
zazenergy3 years ago
wow! very cool!
Joesmania (author)  zazenergy2 years ago
Why thank you zaz! :)