<p>I have been a carpenter for 40 years and cut many rafters. The best way to determine rafter length is to get a book that has rafter lengths because if you step off and are off then the rafter cuts will not be plumb. If it is a gable you could lay out the length on the floor before building the walls. But once you get rafter length you need to account for the ridge and if it is a hip or valley roof then get a good book that illustrates how to make the cuts at the top and birds mouth. on a gable she only change would be to shorten the rafter at the top 1/2 the thickness of the ridge on a level line. For instance draw the plumb cut at the top then place your square on t his line and draw a level line and measure back 1/2 the thickness of the ridge. Using a 2x ridge this would be 3/4 of an inch if it was a 4/12 ridge it would be 1 3/4 .when you make your new ridge cut line you will see at the top or the bottom it is actually more than 3/4 or 1 3/4. If you have a 4-12 slope shorten the rafters maybe 7/8 inch this will be enough but in a steeper pitch roof then you should lay it out</p>
<p>Thank you for pointing that out. I'll take down this instructable showing the mathematical one measure one mark way and get that book. Then I'll put up an instructable on how to carry a book around and use the appendix or something.</p><p>How would that be?</p>
<p>Did you even read this instructable??? There is no where that says to &quot;step&quot; anything off. Also, I describe how to take 1/2 the ridge off of the rafter measuring 90* off of the plumb cut. As for all the rest, seems like you want to be an instructable author yourself. So instead of salting other peoples instructables why don't you make your own, and show how to use your book or snap lines all over the floor and explain how much more efficient and precise those ways are compared to a one measure and one mark system such as the mathematical way my instructable shows...</p>
<p>I have deleted this instructable, thanks to instructables user - &quot;whathappened&quot;. </p><p>He spoiled it for me, and also for all of you by proxy.</p><p>Everyone give &quot;whathappened&quot; a hand !!</p><p>Thank you so much whathappened; From 520,079 people all over the globe.</p><p>Yay, whathappened.</p>
<p>Hey Joe, screw this guy. Don't worry about one persons opinion instead focus on the 500,000 who didn't give you shit for helping people. At our business we sometimes do the same thing where one person will complain so we think we need to do something about it but 100,000 loved it. We learned and now don't give a shit about the one persons complaint :-)</p>
There didn't seem to be much instruction on how to figure where to mark for the plumb cut meeting the peak of the roof. Everything else made perfect sense!!
<p>There are two marks on a common rafters a level line and a plumb line first get to recongize the difference. mark the plumb cut at the top. cut this mark then if the rafter is 14 -6 measure along the rafter this amount and this would be the plumb cut of the seat. cut your birdsmouth which is a plumb cut and a level cut. Draw the plumb cut and then measure down say 4&quot; on a 2/6 and mark a level line.cut out this wedge go back to the top and use the cut mark to measure 1/2 the thickness of the ridge using a level line shorten the rafter this amount and cut it again now you have a pattern</p>
<p>I'm deleting this instructable. Thanks to you. I'll wait 1 day then its down. Take a bow...</p><p> I took a lot of time making this, and was proud of it. Your comments made it seem as you didn't even read it, are trashing it with things that are not even in it, and frankly, are inaccurate and poor practice compared to math.</p><p> Did you realize that you are replying to comments that are far beyond stale too??</p><p> If you want to share your &quot;snapping lines all over the floor&quot; way or how to tote a rafters book with you, why don't you make your own instructable instead of ruining one that 1/2 of a million+ people found to be useful or interesting??</p><p>Now that it's down, can you go troll somewhere else??</p><p>Thanks</p>
<p>Thank you for pointing that out, I've edited that step giving it more detail.</p>
<p>If a building is L shaped with a valley you have to make sure both commons are the correct length or there will be a hump in the roof. A rafter book costs maybe 20 dollars if you can;t afford this then maybe put on a flat roof </p>
<p>Hu??? </p><p>1. Who said anything about not having $20?? </p><p>2. I don't look down on people like you, who like to tote a book around from job to job, why do you look down on folks who like to be self sufficient, and solve mathematical problems for themselves, with knowledge they learned and committed to memory in their own brains?</p><p>And last but not least...</p><p> 3. Why exactly, would the math not work, and put a &quot;hump&quot; in a roof??</p><p>4.You did read the title and see that this instructable is on Common rafters, and not on Hip or Valley rafters I trust..</p><p>5. For me, weather a building is a box, rectangle, a circle, or &quot;L&quot; shaped and weather it has a valley, dormer, or nothing at all..... one would think you would be sure your rafters are the correct length. One would think...</p>
My deck is 66 foot long 16 foot wide how long should the rafters be
<p>It would depend on the pitch you want to put on it .</p>
<p>Thank you for all the useful information you have provided in this forum! My question is in using the formula to figure out the length of the rafter, what would the overhang be for a 5/12 pitch? We are trying to get a take off list for the material required. Thank you for your time!</p>
<p>It would depend on the length of the overhang. Say you have a 24' span and a 2' overhang on a 4-12 slope roof. 1/2 of 24 is 12 then add about 1 foot for rafter length total 13' then 2 feet and you get 15 feet since you can't buy lumber 15' long then get 16' lumber. if you had a 12 - 12 roof slope you would have to get 18' lumber. sometimes maybe get the rafters another 2' longer and use the waste to cut the blocks</p>
<p> <br> <br>i really like this <br> article please keep it up.</p><p><a href="http://www.monacopropertylistings.com" rel="nofollow">immobili in monte carlo</a></p>
Also, when attaching the rafters, where on them do you nail? It seems obvious that you'd insert through the narrow part of the 1 1/2&quot; side into the peak board, but surely more than 1 nail would be required. My framing nailer holds nails up to 3&quot; long. Would I need to buy a gun with longer nails or do I toe-nail from the side or neither of those? ;) thank you for your help!!
<p>16 penny nails are 3/12 inches long Take a rafter and nail it tight to the bottom plate. if you have a helper have him hold the top of the rafter if not hook a nail over the ridge so the rafter will not fall down if you are using 20&quot; rafters it would be better to get some help Then put the top of the rafter in place and nail though the ridge into the rafter brace the ridge before hanging too many rafters on the other side do the same thing but this time start your nail near the rafter you have already nailed to the ridge and drive it on an angle You could also toenail a few nails from the other side if you feel y ou need to </p>
<p>Joe, great instructible! Is it necessary to make two cuts on the ridge beam side of the rafter to remove 1/2 the width of the beam or could you factor that reduction into The original length? Also, do you have a blog on measuring and installing the ridge beam these rafters will tie into? I'm finishing a play house for the kids with a 5/12 roof to match my house!</p>
<p>Thanks for your comment Jlgulley3.</p><p>No you could subtract the full with of the ridge from your buildings overall width, and then continue with the formula, but for ease of explanation in this forum I just chose to show &quot;the cutting it off after&quot; method.</p><p>Unfortunately I have no blog yet, but the thought has crossed my mind, and I just may start one someday... Thanks.</p><p>The measurement of your ridge will be the same as your building length from gable end to gable end. Installation depends on the size, but this generally works for things like sheds and play-houses.... </p><p>Install 3-4 sets of your rafters and let them lean against each-other at the top with an angle brace or two on each side so they wont just flop over. Lay out all of the rafter marks on the ridge (2' O.C. is 23&amp;1/4&quot; to the first one and then every 24&quot; from that first one. 16&quot; O.C. is 15&amp;1/4 and then every 16&quot; from the first.) then push it up from below between the rafters, when you let off on the ridge, the rafters SHOULD bind on it and stop it from falling back down through. Best to have 3 people just to make it a very east task, fewer than that, and it can try your patience.</p><p>Hope that has helped, any other questions.. don't be a stranger! Stop in and ask! </p><p>Post some pics of the play house when your done?</p>
Why do all this math when all you really need is a simple contractor calculator?
<p>Thanks for your question,</p><p>For people who don't want to shell out $50.00 - $100.00 on the calculator, the brain works for free. Scroll down and view the comment from &quot;wills1&quot; and my reply to him for a more comprehensive answer.</p><p>P.S. Why memorize a booklet full of directions for a calculator when all you have to do is some basic math??</p>
<p>could you do it without being a even number like your run is 10 feet 3 and 7/16</p><p>showing how to convert it</p>
<p>I have added this scenario to Step One of the Instructable. Thank you for your feedback and this excellent suggestion. </p><p>Happy framing!</p>
<p>this just saved me a ton of money. i was worried about buying construction calculators and all the bells and whistles just to make a darn common rafter template...thanks, man!!</p>
<p>Oh wow! I couldn't have prompted you to leave a better comment! I liked to use the Construction Master Calculator back in the day, but then I thought... What would I do if I was on a job with a full crew of guys out in the boonies and the thing wasn't working on roof day? Shut the site down and drive 50 miles to Lowes? That's when I learned the old school way, it isn't much slower than the fancy calculator, and it always works... Thanks for the comment, and happy framing!</p>
<p>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.</p>
<p>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.</p><p>Joe.</p>
<p>Hi, thanks for this article. You made the process so simple. Do you have instructions on how to make valley rafters? </p>
<p>I signed in with Google+, and it gave me a different user name... JoeS3. I didn't realize it until I hit the &quot;Make Comment&quot; button. Needless to say, the reply back to you from JoeS3 was me.</p><p>Thanks again.</p><p>Joe.</p>
<p>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 &amp; 3/4&quot;. In hind sight, I only give the mathematical process for foot increments. </p><p>It is on my list, and your interest may just be the motivator I needed.</p><p>Thanks again, J.</p>
Thanks for the feedback BIG - X
wow! very cool!
Why thank you zaz! :)

About This Instructable


66 favorites


More by Joe Smania:
Add instructable to: