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How do I sister a joist?


amateurplumber's Avatar
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08-04-14, 09:40 AM   #1  
How do I sister a joist?

As you can see, some dummies took a notch out of the center joist in my shower, and it was also damaged by water. I would like to sister it. I can't sister the entire length. The most I can access is that 3-4 foot section you see. As I understand it, I just glue the two together, then drill a hole and bolt some bolts in. Questions:

1)How many bolts should I use?
2)What size bolts should I use?
3)What type of bolt should I use?
4)Do you guys have any other tips or anything?

Thanks a ton!

 
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08-04-14, 11:06 AM   #2  
I would say 8 each, 3/8" x 4" carriage bolts, with fender washers and nuts.
Place 2 bolts at each side of trap, about 2" from top and bottom of joist.
Place the other 4 bolts at about 2/3 the way out towards each wall.

I looked at the pictures, this joist still has integrity in my opinion. I've seen much worse.
You can jump on it and test it after repair, to me it doesn't look like it would have any deflection.

 
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08-04-14, 11:33 AM   #3  
Thanks for the advice! You do think it's necessary to sister it, though, don't you? It seems pretty solid when I stand on it. Just as much as the other ones. But everyone told me to sister it so here I am! Thanks again!

 
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08-04-14, 11:37 AM   #4  
You have it open and exposed, so just sister it. The material cost is minimal and elinamtes some future problems because moisture exposure in the future is problematic.

Dick

 
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08-04-14, 11:40 AM   #5  
I'm not so sure you need to bolt it? On several of the reputable improvement shows, when they sistered joists, they just used construction adhesive and either screws or a nail gun with the boards clamped together temporarily. Once the adhesive sets, no way will the boards ever separate.


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08-04-14, 12:08 PM   #6  
Got to agree with Gunguy,

I was going for the overkill. Pretty much anything you do to beef this up will be more than enough.

 
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08-04-14, 12:29 PM   #7  
Ha! I meant on the left side! I just want to be done with this and am scared stuff wont be right! I do think that other thing should be alright, though!

I would screw the sistered joists together, but I know that's not allowed.

 
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08-04-14, 12:33 PM   #8  
Sorry, I mis-read your other post.


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08-06-14, 05:51 PM   #9  
I should use nails over screws when sistering, right? I have read 16d nails are used most of the time so I got those. How many nails should I do (what pattern)? Thanks!

 
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08-06-14, 06:33 PM   #10  
If you are using adhesive, 16d is pretty much overkill. You have them, so just use them.

6-8 inches on center in a W pattern should be fine. All you really need to do is hold the wood together til the adhesive cures.


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08-06-14, 06:53 PM   #11  
Cool, thanks! I can always get small nails. I'm at the hardware store constantly haha. I've also read 10d. Thanks gunguy!

 
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