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Old 04-19-2017, 10:23 PM   #1
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Rotten Floor Beam


I am currently replacing part of a wall under a window that rotted out due to a leaking window sill and some white fungus.

I noticed that one of the beams/joists is rotted where it sits on the sill plate. The other two joist on either side are solid. What is the best way to repair this? The length from sill plate to center beam is about 12 ft.

If I sister it how far back should I run the sister? I know 12 ft is ideal but can I get away with say 6 ft and several bolts? Also should I completely cut out the rotted end, chip away at the rot with a claw or maybe use some wood hardening agent to solidify whats left.
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Old 04-19-2017, 10:34 PM   #2
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Re: Rotten Floor Beam


A picture is going to help us to advise you on this, right now we will just throw whatever sticks at this query.

ED
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Old 04-19-2017, 10:59 PM   #3
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Re: Rotten Floor Beam


Yeah, I wish I snapped one today. I will take a pic in the morning
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Old 04-20-2017, 10:36 AM   #4
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Re: Rotten Floor Beam


Here are some pics of the rotten joist. The first two pictures are from left side, then the middle and the rest are from the right side. The white fungus stuff is the same as was on the rest of the wall components from the leaking sill.
Attached Thumbnails
Rotten Floor Beam-20170420_101412.jpg   Rotten Floor Beam-20170420_101420.jpg   Rotten Floor Beam-20170420_101442.jpg   Rotten Floor Beam-20170420_101524.jpg   Rotten Floor Beam-20170420_101513.jpg  

Rotten Floor Beam-20170420_101519.jpg  

Last edited by James8153; 04-20-2017 at 10:39 AM.
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Old 04-20-2017, 12:26 PM   #5
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Re: Rotten Floor Beam


Are there any obstructions in the way along the 12 ft length?
Plumbing?
Electrical?
Heat ducts?

Since you have access, apparently as per the pictures, why not sister the entire length?
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Old 04-20-2017, 12:44 PM   #6
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Re: Rotten Floor Beam


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Originally Posted by jlhaslip View Post
Are there any obstructions in the way along the 12 ft length?
Plumbing?
Electrical?
Heat ducts?

Since you have access, apparently as per the pictures, why not sister the entire length?
I don't think I have any obstructions. However the crawl space is tight and not that easy to get under. If I do sister the joist do I need to cut out the rotted end? The water intrusion is fixed.

Have you any experience with PC Rot Terminator 2 part epoxy? Supposedly it works on structural members. http://www.homedepot.com/p/PC-Produc...0618/100649635. If that stuff works it would be a lot easier than sistering.

Last edited by James8153; 04-20-2017 at 12:47 PM.
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Old 04-20-2017, 12:54 PM   #7
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Re: Rotten Floor Beam


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Originally Posted by James8153 View Post
I don't think I have any obstructions. However the crawl space is tight and not that easy to get under. If I do sister the joist do I need to cut out the rotted end? The water intrusion is fixed.

Have you any experience with PC Rot Terminator 2 part epoxy? Supposedly it works on structural members. http://www.homedepot.com/p/PC-Produc...0618/100649635. If that stuff works it would be a lot easier than sistering.
Yes, removing the rotted stuff, or at least treating it with a cure, is a good idea.

No experience with that epoxy.
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Old 04-20-2017, 02:38 PM   #8
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Re: Rotten Floor Beam


Just went under house and as suggested will cut out rotten joist end and sister new joist. However my only issue is that the original joist is 7" high x 2 3/8" exactly. A new 2x8" or 3x8" as you know is 7 14 inches high. I know notching a joist on the end is not great but would taking off a 1/4" make any difference?
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Old 04-20-2017, 03:19 PM   #9
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Re: Rotten Floor Beam


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Originally Posted by James8153 View Post
Just went under house and as suggested will cut out rotten joist end and sister new joist. However my only issue is that the original joist is 7" high x 2 3/8" exactly. A new 2x8" or 3x8" as you know is 7 14 inches high. I know notching a joist on the end is not great but would taking off a 1/4" make any difference?
Notching is not the same as taking a 1/4" off the entire board. You're essentially just changing the size of the board but that shouldn't matter since you're doing it to match what's currently there. Put it on a table saw and get a good straight cut.

Good luck!

-Mark
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Old 04-20-2017, 05:50 PM   #10
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Re: Rotten Floor Beam


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Originally Posted by Marky82 View Post
Notching is not the same as taking a 1/4" off the entire board. You're essentially just changing the size of the board but that shouldn't matter since you're doing it to match what's currently there. Put it on a table saw and get a good straight cut.

Good luck!

-Mark
Actually I did mean notching as I don't have a table saw but only a circular saw. So is there a big difference if I just take out 1/4" from the last 3 inches of each end? Trying to take 1/4" off the entire 12 ft length with my $40 circular saw may be asking for trouble.
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Old 04-20-2017, 07:05 PM   #11
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Re: Rotten Floor Beam


The ends of the beam carry no bending moment, you can cut 1/4 inch down on the ends with no problem.
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Old 04-21-2017, 01:58 PM   #12
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Re: Rotten Floor Beam


Keep in mind that new wood can have more moisture than old wood, so that the new wood shrinks a little as it dries. This is why your old joists and new lumber aren't the same size. If you put in a wet joist that is the same size now as your old one, you might just have a dip in a couple years.
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Old 04-22-2017, 09:52 PM   #13
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Re: Rotten Floor Beam


Thanks for all the tips. Finished the job today. For anyone else who may need to do this, this is how I did it. I cut off the rotted part and cleaned off the old board with tor-bor and let it dry. I used an 8x14 (cut to size) and sistered it to the old board with 8 x 1/2" bolts, construction adhesive and nails. Key was to jack up the new board at the end nearest the center beam so it would fit tight against the sub floor and even with the old joist.
I would have preferred to run the new joist across the center beam but getting it on the beam was too much work as it was not an easy fit.
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