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Old 06-26-2013, 05:04 PM   #1
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Simple rafter layout question


I'm framing my porch this weekend and am not sure how to layout the rafters efficiently. The rafters (on their uphill side) will attach to a ledger on the exterior wall of the cabin, and then I have a honkin' 8x8 plate that the rafters will be attaching to on their downhill side. The rafters will be tied into the ledger with joist hangers, and into the plate with a birds mouth joint and long timberloks. If I have the height of both sides of attachment, then I can get my slope. Might anyone have any tricks for how to layout off of that slope? I imagine the slope will be something wild, like 3.82, so the speed square doesnt seem too accurate. And how to know precisely where to put the birds mouth?

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Old 06-26-2013, 07:32 PM   #2
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Simple rafter layout question


No clue what your trying to describe.
A down hill side on a rafter?
Using Timberloks on rafters?
Got some pictures.

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Old 06-26-2013, 07:47 PM   #3
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Simple rafter layout question


If I'm understanding correctly, you're looking for how to figure out the pitch? So once you know the angle you can layout the birds mouth?

These might help:
http://www.thisiscarpentry.com/2012/...after-framing/

http://www.sbebuilders.com/tools/hap.php
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Old 06-26-2013, 10:45 PM   #4
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Simple rafter layout question


I cheat---I often use a no math method---I'm to tired to spell it out--but I tack two blocks to the wall to represent the ridge(ledger in your case) and the top plate---then hold the rafter against the blocks and draw the cut--

All from the ground--then test it. If you blocks are exactly like the ledger and top plate--it will be right.
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Old 06-26-2013, 11:22 PM   #5
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Simple rafter layout question


I'm all for KISS methods.
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Old 06-27-2013, 07:11 AM   #6
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Simple rafter layout question


I had a similar issue when building my log house. It has three covered porches, each with a slightly different depth and roof pitch. The rafters are 4x8 beams, so I really didn't want to mess one up and have to buy another. Though I'm an engineer, I've never been able to make sense of all the markings on a speed square. So I drew everything out using AutoCAD and took the angles and measurements from that.
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Old 06-27-2013, 08:13 AM   #7
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Simple rafter layout question


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Originally Posted by md2lgyk View Post
I had a similar issue when building my log house. It has three covered porches, each with a slightly different depth and roof pitch. The rafters are 4x8 beams, so I really didn't want to mess one up and have to buy another. Though I'm an engineer, I've never been able to make sense of all the markings on a speed square. So I drew everything out using AutoCAD and took the angles and measurements from that.
I'm with MD2..... Although I don't have autocad.... I could never remember my sign/cosign etc relationships and my calculator settings... so my brother in law just wrote me a very simple trig program.... where all I have to do is put in my hard (measured) figures or angles, and it spits out all my other dimensions.

Also, I love my level that will report my slope... in angle, %, and X/12.
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Old 06-27-2013, 12:39 PM   #8
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Simple rafter layout question


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I had a similar issue when building my log house. It has three covered porches, each with a slightly different depth and roof pitch. The rafters are 4x8 beams, so I really didn't want to mess one up and have to buy another. Though I'm an engineer, I've never been able to make sense of all the markings on a speed square. So I drew everything out using AutoCAD and took the angles and measurements from that.
Frankly, if I have the opportunity, that is the way I handle most things anymore. It also helps me see things I might otherwise miss.
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Old 06-27-2013, 12:54 PM   #9
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Simple rafter layout question


Pretty comprehensive article on rafters here.
http://www.thisiscarpentry.com/2012/...after-framing/
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Old 06-28-2013, 06:43 AM   #10
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Simple rafter layout question


A couple of T-Bevels and some tight string helped me get through my hip & jack rafter cutting.
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Old 06-29-2013, 12:16 PM   #11
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Simple rafter layout question


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Originally Posted by danf26 View Post
I'm framing my porch this weekend and am not sure how to layout the rafters efficiently. The rafters (on their uphill side) will attach to a ledger on the exterior wall of the cabin, and then I have a honkin' 8x8 plate that the rafters will be attaching to on their downhill side. The rafters will be tied into the ledger with joist hangers, and into the plate with a birds mouth joint and long timberloks. If I have the height of both sides of attachment, then I can get my slope. Might anyone have any tricks for how to layout off of that slope? I imagine the slope will be something wild, like 3.82, so the speed square doesnt seem too accurate. And how to know precisely where to put the birds mouth?
Can you give us the measurements of the length of the outside of the 8x8 to the inside of the ledger and also the height from the top of the 8x8 to the top of the ledger?
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Old 06-29-2013, 12:28 PM   #12
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Simple rafter layout question


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Can you give us the measurements of the length of the outside of the 8x8 to the inside of the ledger and also the height from the top of the 8x8 to the top of the ledger?
Good idea...Joe..... Plus it'll be fun to see how many different answers we all come up with
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Old 06-29-2013, 01:21 PM   #13
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Simple rafter layout question


Being the slope is going to be something wild like 3.82 just keep it simple and make it a 4/12 pitch. Then determine the run, the horizontal distance from the ledger to the outside of the top plate, and use the step off method to lay out a pattern rafter. You will only need your tape measure to determine the run and you certainly won't need a calculator or any of those modern tools called programs.

http://www.finehomebuilding.com/how-...f-framing.aspx


Last edited by Fairview; 06-29-2013 at 01:24 PM.
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