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Attic rafter sistering
#4105518
03/23/24 07:23 AM
03/23/24 07:23 AM
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Joined: Jun 2015
Posts: 14,048 Some Marriott/Auburn
AU7MM08
OP
Booner
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OP
Booner
Joined: Jun 2015
Posts: 14,048
Some Marriott/Auburn
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My house was built in 1978 and has one attic rafter that has a crack, I’m going to scab/sister a board on either side and then attach it with 4” structural screws, I plan to also use a glue so that I have a mechanical and chemical bond.
Should I use wood glue/Gorilla Glue or construction adhesive/Liquid nails for the glue part of my project?? Or does it not really matter and flip a quarter to determine which adhesive to use?
Thank you
Last edited by AU7MM08; 03/23/24 07:24 AM.
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Re: Attic rafter sistering
[Re: AU7MM08]
#4105532
03/23/24 07:48 AM
03/23/24 07:48 AM
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Joined: Jan 2005
Posts: 14,320 Hoover
Fattyfireplug
Booner
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Booner
Joined: Jan 2005
Posts: 14,320
Hoover
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No matter what project I work on, I use the strongest glue possible unless there is a possibility I might have to take it apart. Construction Adhesive would be my choice.
Character is not developed in moments of temptation and trial. That is when it is intended to be used.
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Re: Attic rafter sistering
[Re: AU7MM08]
#4105540
03/23/24 08:04 AM
03/23/24 08:04 AM
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Joined: Oct 2009
Posts: 5,721 Henry county
coldtrail
12 point
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12 point
Joined: Oct 2009
Posts: 5,721
Henry county
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I would lag some steel to it. A piece of six flat bar with some lags or better yet bolt through with 3/8 bolts. It may be over kill but it will hold.
"And the days that I keep my gratitude Higher than my expectations Well, I have really good days" Ray Wylie Hubbard
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Re: Attic rafter sistering
[Re: Irishguy]
#4105572
03/23/24 08:56 AM
03/23/24 08:56 AM
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Joined: Jun 2015
Posts: 14,048 Some Marriott/Auburn
AU7MM08
OP
Booner
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OP
Booner
Joined: Jun 2015
Posts: 14,048
Some Marriott/Auburn
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I agree with the Titebond III.
Those construction screws you are talking about, if it's a #22x4 in 1.5" thick Southern Pine, each have a shear capacity of about 400 pounds. So you are probably going to be good without the glue.
I would extend reinforcement members at least 12" past the crack on each end.
Keep in mind that rafter is only supporting the contributory area of that one rafter, which would be half the distance between it and the nearest two rafters. So let's say that the rafters are 16" apart and the length is 20'. That's a worst case area of 26 square feet of contributory area. Apply a load of 30# per square foot including live load and dead load and you are only talking about that single rafter supporting a total load of 780 pounds.
So you should be good to go.
Thank you for the engineering explanation.
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Re: Attic rafter sistering
[Re: AU7MM08]
#4105636
03/23/24 10:30 AM
03/23/24 10:30 AM
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Joined: Mar 2016
Posts: 3,624 Spanish Fort
TurkeyJoe
10 point
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10 point
Joined: Mar 2016
Posts: 3,624
Spanish Fort
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I would nail the boards on instead of screwing them. Screws do not have any ductility, so I personally wouldn’t use them for that application.
Micah 6:8
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Re: Attic rafter sistering
[Re: AU7MM08]
#4105648
03/23/24 10:43 AM
03/23/24 10:43 AM
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Joined: Sep 2007
Posts: 7,608 Hartselle, AL
trlrdrdave
14 point
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14 point
Joined: Sep 2007
Posts: 7,608
Hartselle, AL
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ductility...I learned a new word. Guess that's why I can answer electrical questions and not carpentry ones.
"In time of war, send me all the Alabamians you can get, but in time of peace, for Lord's sake, send them to somebody else." General Edward H. Plummer
"Blessed are those who, in the face of death, think only about the front sight." Jeff Cooper
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Re: Attic rafter sistering
[Re: AU7MM08]
#4105654
03/23/24 10:49 AM
03/23/24 10:49 AM
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Joined: Aug 2003
Posts: 42,181 UR 6
top cat
Freak of Nature
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Freak of Nature
Joined: Aug 2003
Posts: 42,181
UR 6
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Build a hog through with a couple 8' 2x4s. Screw it centered on the cracked rafter and then to the other rafters they cross. Glue is not the answer X
LUCK:::; When presistence, dedication, perspiration and preparation meet up with opportunity!!! - - - - - - - -A government big enough to give you everything you want, is big enough to take everything you have. Thomas Jeferson - - - - - - - -
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Re: Attic rafter sistering
[Re: TurkeyJoe]
#4105655
03/23/24 10:49 AM
03/23/24 10:49 AM
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Joined: Mar 2012
Posts: 3,345 Here
Okatuppa
10 point
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10 point
Joined: Mar 2012
Posts: 3,345
Here
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I would nail the boards on instead of screwing them. Screws do not have any ductility, so I personally wouldn’t use them for that application. Whatchutalkinboutwillis?
I ain't fightin nobody that swings around in trees with a running chainsaw like Tarzan. - FurFlyin
Oh I just thought u were a dumba$$ 🤣 my apologies… - jb20
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Re: Attic rafter sistering
[Re: AU7MM08]
#4105725
03/23/24 02:22 PM
03/23/24 02:22 PM
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Joined: Dec 2004
Posts: 18,865 .
ford150man
Old Mossy Horns
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Old Mossy Horns
Joined: Dec 2004
Posts: 18,865
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Make sure you drill a hole at the very end of the crack to prevent it from running, before you scab it.
If voting made any difference, they wouldn’t let us do it.-Mark Twain
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Re: Attic rafter sistering
[Re: AU7MM08]
#4105726
03/23/24 02:25 PM
03/23/24 02:25 PM
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Joined: Jul 2011
Posts: 34,591 Boxes Cove
2Dogs
Freak of Nature
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Freak of Nature
Joined: Jul 2011
Posts: 34,591
Boxes Cove
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Regardless of how you do it , if you wanta glue wood Titebond is the glue to use.
"Why do you ask"?
Always vote the slowest path to socialism.
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Re: Attic rafter sistering
[Re: Okatuppa]
#4105732
03/23/24 02:36 PM
03/23/24 02:36 PM
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Joined: Mar 2016
Posts: 3,624 Spanish Fort
TurkeyJoe
10 point
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10 point
Joined: Mar 2016
Posts: 3,624
Spanish Fort
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I would nail the boards on instead of screwing them. Screws do not have any ductility, so I personally wouldn’t use them for that application. Whatchutalkinboutwillis? Ductility is a material’s ability to bend without breaking. Important for applications facing high wind load like a roof or exterior wall.
Micah 6:8
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