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Old 10-18-2009, 07:35 PM   #16
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Ya i have a program that tells me what i need to cut for a 5/12 but the angle seems wrong but i think maybe it just looks wrong until i cut the birds mouth. I drawing it in autocad right now to see what i'm doing wrong. Both runs are 5'-10 3/4 now no more 5' and 6' made them the same .

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Last edited by Kurt1968; 10-18-2009 at 07:58 PM.
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Old 10-18-2009, 09:41 PM   #17
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this is a gable or a hip, the math will be hard to figure when the center is not exact, but an eyebrow hip is in a sense adjustable!!
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Old 10-19-2009, 02:01 AM   #18
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Originally Posted by Kurt1968 View Post
Alright now how do i figure the rafters its not coming out right. My run is 5'-10 3/4 the rise is 32". Thats what the rise has to be. I know its going to be some bastard size. Thats what you get when you own a 105 year old house.
What size rafters are you using? That will determine what the pitch is since you have a fixed height of 32" because of the HAP cut (Height above Plate). This is the Vertical measurement after you make the seatcut on the birdsmouth at the 5'10-3/4" run.

This is where Architects will make mistakes when calling out a certain pitch and a fixed ridge height but they don't allow for the HAP cut height and the rafter with, whether your using a 2x6, 2x8 or 2x10. This all makes the difference right there.

For example, you have a 5' 10-3/4" run and you want to use a 5/12 pitch. This would give you a 29.47917" rise if it was just a simple triangle. Now depending on what size rafter you use and if you layout a 3-1/2" level seatcut, adding the vertical HAP cut height can put you over your 32".

If you use a 2x6 rafter and layout a 3-1/2" level seatcut, that will give you a 4-1/2" HAP cut. Add that to the 29.47917" rise and you will have exactly 33.9375" or 33-15-16"" rise. Add another 5/8" -3/4" for sheathing if using 5/8" sheathing.

If you use a 2x8 rafter and layout a 3-1/2" level seatcut, that will give you a 6.666667" or 6-11/16" HAP cut. Add that to the 29.47917" rise and you will have a 36.14583" rise. Add another 5/8" -3/4" for sheathing if using 5/8".

The first drawing is a 2x6 rafter and a 5/12 pitch. The second drawing is a 2x8.
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Old 10-19-2009, 07:46 AM   #19
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Thanks dude your awesome. Not to be a pain but can you give me the lengths of the rafters and where to make the cuts. I'm using 2x6's. For elk this roof is attaching right to the house its a wrap around porch.

Last edited by Kurt1968; 10-19-2009 at 07:51 AM.
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Old 10-19-2009, 07:50 AM   #20
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Kurt,

There are many ways to figure this out mathematically and they will always work. In your situation, all you have to do is nail your ledger board onto the house about 3/4 lower than your fixed height which would 31-3/4". That's not including the sheathing. If you can't be any higher than 32" including the sheathing and roofing with proper flashing do to windows above, you have to lower the ledger.

Once you have the ledger in place and the girder set, all you need to do is take a rafter pattern and scribe a 5/12 plumbcut for now and cut that because it's close enough. Set yourself up and someone else up with a ladder at the girder and ledger at the end.

Take the 5/12 plumbcut end and stick it past the ledger until it hits the sheathing with the top of the rafter flush to the inside of the ledger. Have your helper hold the bottom of the rafter flush to the inside of the top of the girder and scribe the level seatcut on the top of the girder and scribe the vertical HEEL cut on the outside of the girder. This will give you your birdsmouth and full seatcut. You will scribe the inside of the ledger and that will give you your plumbcut and pitch of the roof.

Doing this gives you the exact length and pitch of the rafter. You will then add whatever you overhang is past the HEEL cut. Use that rafter as the pattern and scribe every common rafter for the entire roof.

Depending on what size rafter you use, the pitch might work out to be a 4-5/8;12. If it is, the plumbcut on the hip at the top and the birdsmouth will be 4-5/8:17.

Hope this helps
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Old 10-19-2009, 10:14 AM   #21
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Thanks joe for all your help its starting to make sense now. I just makes me feel stupid. I cant figure this out . If i was a carpenter instead of a tool & die maker. It would be easier.
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Old 10-19-2009, 10:26 AM   #22
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all that it is , math. Wrap around will give you 2 outside corners do deal with and thats where the hips will be.........The house wall are high enough that the porch roof attaches with ledgers and your plumb cuts nail into those but many variations here good luck dude!!
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Old 10-19-2009, 01:22 PM   #23
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Quote:
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Thanks dude your awesome. Not to be a pain but can you give me the lengths of the rafters and where to make the cuts. I'm using 2x6's..
Kurt,

Using 2x6 and a 5' 10-3/4" run from the sheathing, your pitch will be 4-5/8:12. That will give you a total rise to the bottom of the sheathing of 2' 7-13/16". Add your 2x8 ledger which will reduce the run by 1-1/2", that will set your ledger height at 2' 7-1/4". Your rafter length from the back of the ledger to the outside of the girder will be 6' 2-13/16" not including your overhang because I didn't know what it was.

Add your overhang in and use that rafter as a pattern. Tack your ledger up at the height I said and cut a few rafters and make sure they fit. Make sure your girder is straight because if not your rafters can be up and down a little at the ledger. Always nail the birdsmouth tight to the girder so that the overhang stays the same.

Your hip will be cut with the framing square held on 4-5/8:17, or 15.24 with a speedsquare. The Hip length will be 8' 5-1/2". I'll show you how to mark the HAP cut on that because it's a little different.
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Old 10-19-2009, 01:25 PM   #24
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Thanks joe for all your help its starting to make sense now. I just makes me feel stupid. I cant figure this out . If i was a carpenter instead of a tool & die maker. It would be easier.
Kurt,

There's no reason at all to feel stupid. It's not what you do for a living. Your asking the right questions. That's the smartest thing to do right there. Hope I can help you more.
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Old 10-19-2009, 01:36 PM   #25
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My overhang is going to be 1'.
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Old 10-19-2009, 02:35 PM   #26
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My overhang is going to be 1'.
Here you go.Are you using a 2x sub-fascia and a 1x6 fascia?
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Old 10-19-2009, 03:08 PM   #27
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Yes on the fascia. What program are you using for this?
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Old 10-19-2009, 03:15 PM   #28
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Yes on the fascia. What program are you using for this?
I'm using SketchUp 7. Free download.
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Old 10-19-2009, 03:24 PM   #29
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Thanks again for all your help. I will post pictures when i get the rafters up there.
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Old 10-19-2009, 07:55 PM   #30
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I'm using SketchUp 7. Free download.
I notice that you have shown a 2X4 plate on top of the laminated beam.

I recently finished a similar project like this. My beam was laminated using 3-2X10's. I didn't use the 2X4 plate for mine.
I fastened the rafters to the beam directly using 'Hurricane Clips'.
Was this a mistake on my part?

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