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Old 03-01-2011, 10:54 PM   #1
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rafter question


I'm building my house w/ lumber that I made on a one-man sawmill. My question invovles the rafters. The second story roof is 12/12. Nominal 2x6 rafters. Nominal 2x8 ridge board. the bird's mouths are perfect, and most plumb cuts are tight at the ridge board, but some have a 1/8'' or less gap at bottom of plumb cut at the ridge, however not all of them have this and they were all cut off the same pattern rafter crown up. could this be caused by the crown of the rafter and will it settle the gap as the crown settles or should I shim, or redo the rafters? I want to stop stressing over this so I can put up the rest of the rafters and move on, so any help would be greatly appreciated. Thanks.
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Old 03-01-2011, 11:27 PM   #2
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rafter question


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Originally Posted by roughsawn View Post
I'm building my house w/ lumber that I made on a one-man sawmill. My question invovles the rafters. The second story roof is 12/12. Nominal 2x6 rafters. Nominal 2x8 ridge board. the bird's mouths are perfect, and most plumb cuts are tight at the ridge board, but some have a 1/8'' or less gap at bottom of plumb cut at the ridge, however not all of them have this and they were all cut off the same pattern rafter crown up. could this be caused by the crown of the rafter and will it settle the gap as the crown settles or should I shim, or redo the rafters? I want to stop stressing over this so I can put up the rest of the rafters and move on, so any help would be greatly appreciated. Thanks.
I wouldn't worry about a gap of 1/8" or less.
Ron
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Old 03-01-2011, 11:42 PM   #3
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rafter question


Thanks. I try not to sweat the small stuff, but this is my first time building a house, and it is my hous, or should I say my wife's house, so I'm building it to last, hopefully. the building inspector wont be back from florid til april and I don't want him to take issue. I don't know if this gap is normal cause like I said I've never done this before. Inspector probably wouldn't like shims sticking out everywhere, so I guess I'll leave as is and keep going.
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Old 03-02-2011, 08:20 AM   #4
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rafter question


Yep, save your shims for the cabinets.
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Old 03-03-2011, 10:24 PM   #5
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Some tips for you, pp. 51; http://books.google.com/books?id=iwS...rafter&f=false

Installing drywall on green wood; http://www.paintsource.net/pages/sol...ood_shrink.htm


Gary
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Old 03-04-2011, 01:00 AM   #6
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thanks for the info. However I didn't see anything in there about the rafter gaps.
It is very confusing to me because not all of the rafters have this small gap at bottom of plumb cut and the birdsmouths are tight as can be across the seat and plumb. I cut them all off the same pattern rafter which was a perfect fit on both sides of the ridge board. This leads me to think that maybe when I marked the ridge plumb cut on a 12/12 the crown of certain rafters is perhaps a little more pronounced and is throwing the plumb cut off by a degree. I'm hoping the crowns will settle and close this gap, but if not I can always go up there and shim the gaps to avoid cracking of the rafter due to the downward force. What do you think? Rough sawn wood definitely presents its own challenges. But it is solid as can be. I'm lucky even to be using it as it is against the code here, but my inspector is a nice guy who understands my situation. No mortgage, no money to speak of but lots of trees and determination, and woodpeckers.
Oh, and I won't be using drywall. Not enough in the pocket budget, but I can see where some shrinkage mitigation measures could be taken. If I run my 1x sheathing on 45's and leave a 1/2 in gap in the middle of the rim joist between stories that should take care of any buckling? I already made sure to put a piece of 2x of cedar on top of all piers beneathe the white oak beams to keep the shrinkage of the middle of the house even w/ the sill walls, the sill being cedar as well, but I hadn't even thought of the sheathing buckling. All headers are solid 6x10 white pine beams, so I don't think I will have a problem there. Half my floor joists are 2x8 of red maple and white pine, and the other have are flat top white pine logs, but they are the first things I cut. They shrank from 2 to 1 5/8 before I put them up because the were stickered out in the sun all summer. I don't think they will shrink much more. The studs are all red pine which I find to be very stable and hard when dry w/ little shrinkage, but the white pine really shrinks. I cut my rafters out of norway spruce and that seems to be pretty stable as well but leaks a lot of sap as it dries so I have yet to see what that shrinks like. Anyway, thanks for the info I can still put the shrinkage info to use regardless of the drywall. I've been going through the frame putting 4" screws into everything to tighten it up. Hopefully that will help as well.
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Old 03-04-2011, 06:26 PM   #7
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With the gap at the bottom weight (dropping) the top will make it worse. Check your mid-span walls for straight line, a sting-line set inside, below the top plate- 1-1/2" away. The walls may be bowing out to lower the ridge (check for sags by eye from either end 1-1/2" above and off center of top of ridge board). OR, the template used was not a full length pattern, tacked on the already cut seat cut end. A short pattern is easy to end with different angles. Or, the sides of some boards were not parallel, resulting in off-angles. No gaps at rims, they will surface there later; http://www.buildingscience.com/docum...d-but-strange/

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Old 03-04-2011, 06:34 PM   #8
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Don't sweat it, GBR

an 1/8" gap can come from several places
as long as the top edge of your rafters are in plane, you're good
Use 1-1/2" shims to fill the gaps
If you're good, you'll insert them from the bottom and trim them so they are hard to even see. It's done all the time.......

try to enjoy the experience
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Old 03-04-2011, 07:09 PM   #9
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LOL, I'm not, that's how I answer when some says; "very confusing to me because not all of the rafters have this small gap"----- "crown of certain rafters is perhaps a little more pronounced and is throwing the plumb cut off by a degree."------ "if not I can always go up there and shim the gaps to avoid cracking of the rafter"------ and especially; "What do you think?".

I've had Inspectors require shims other than non-structural "cedar", and they were/are right, LOL.

Gary
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Old 03-07-2011, 09:28 AM   #10
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What do mean by shims other than nonstrductural "cedar" ? And what's w/ all the quotes? I don't think I was being irrational by wondering about the crown. I mean a 1/8" crown or more over an 8' span could show up in plumb cut. At least its a rational idea.
I did follow your suggestion and check the walls w/ a line. Walls are straight and true. There is really nowhere for them to move to as my lower story rafters are jacked in the upper story walls on either side w/ collar ties at floor level. It's like two triangles holding up a third triangle. I could see some sag maybe in fifty years like the old farmhouses around here, but I doubt it. They usually have rafters 2' oc w/ collar ties every other if that. My rafters are 16 oc and have collar ties every pair bottom 1/3 and top 1/3.
My pattern rafter is not short. And I did not make my pattern by tacking it to the end and scribing. I set my ridge height using pythagorean theorum plus hap, minus half ridge thickness, then cut laid out my common w/ a steel square and the step-down method. That was my pattern. And it fit like a glove.
Ridge is level, no sag.
Anyway I don't understand what is so "lol" about my questions. I'm just trying to figure something out and get some feed back. Thanks anyway.
And tcleve4911, I really am enjoying the building experience. There is nothing like the satisfaction of building your own home.
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Old 03-07-2011, 10:34 AM   #11
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I have built with green lumber when i was young enough to handle it. sounds like you have everything under control, nobody was mocking just helping. a cedar shim is not considered structural due to lack of compressive strength, a shim ripped from your rafter stock and inserted between rafter and beam will fill your gap for now. Green air dried lumber is still going to move alot, you may want to consider intermediate blocking on walls and rafters mid span.
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Old 03-07-2011, 02:23 PM   #12
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rafter question


An 1/8th inch is nothing, the width of a match. You can use a Simpson rafter tie if it'll make you & the inspector comfortable.
If you had a buddy holding & marking one end of the rafter off the pattern, maybe he slipped.
One slip with the saw can make an 1/8th inch gap.
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Old 03-07-2011, 04:03 PM   #13
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Sorry roughsawn, I was answering post #8, not you. I was showing him you asked some good questions with my "quotes". The shim comment was for him also, Inspectors can ask for other than cedar species shims because they are not structural. My whole post #9 was not to you. Sounds like you have it under control.

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Old 03-07-2011, 05:27 PM   #14
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Ceiling rafters, mid height collar ties, ridge board, shear and pullout strength of the nails, it aint goin nowhere. Sounds like your doing well. Wish I had the youth and resources. Ive been building for 35 years and not having fun in this economy. Oh well I get to help people on this forum
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Old 03-07-2011, 10:29 PM   #15
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thanks for clarifying. I misunderstood. When I found this site I was hoping to get
good advice...sounds like I'll be able to. Saw slip may very well be the problem. I tried cutting them w/ a circular saw but It kept wanting to pull to the side cutting on 45 degrees, so I have been using a hand saw. Maybe I should make a mitre box out of 2x8's to use as a guide for better cuts. My wood is frozen and that makes it a little harder to cut. I don't have a helper, but maybe I move the pattern unnoticeably by myself and that is my problem. I'll just keep cutting and figure it out. But anyways I'm glad you all agree that a small gap is no issue. Makes me less concerned. However I will still try my hardest to get the best cuts possible. I've got 10 more rafters to cut out of 44 and then on to the decking. Thanks all.
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