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Old 09-12-2017, 01:48 PM   #1
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Repairing a Notched Floor Joist


Hello all,

So I have been trying to do some research on what to do about some notched joists in the basement. These came up on the inspection and were noted "improper notching." I have seen a variety of answers on sistering joists. It is about a 10ft span, using 2X8s. There are 4 joists with the same notches, 2 notches about an 1.5 in apart, each notch is about 1.5 in wide and 2.25 in high. There is very very minimal sagging (if any) and the notches seem to have been there for over 10 years.

My question is, can I get away with doing a partial sister? There are some gas pipes in the way so doing a full sister is not going to happen without some serious work. The partial sister would be about 2ft 9 in on one side (touching the wall) and could go about 4-5ft on the other side. I'm also wondering if I could do the partial sister, put another 2x8 to finish the sister, then on the other side of the joist, bolt/nail those 2 pieces together with another piece of 2x8.
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Old 09-12-2017, 02:05 PM   #2
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Re: Repairing a Notched Floor Joist


You are not worried about sag you are worried about a weak spot that can break under a lesser load than it should.
When you load a joist and it sags a little the top is under compression and the bottom is under tension. When you have a notch it may just bend at the notch instead of sagging and that is when it breaks .

Anything you can do to replace that tension area will work Even 2x4 on flat glued and screwed to the bottom of the joist to make an upside down T will do it.
Engineers were usually happy with 3 or 4 feet of 3/4 plywood or 2x joist nailed and glued to one side. lots of nails.
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Old 09-12-2017, 02:17 PM   #3
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Re: Repairing a Notched Floor Joist


Quote:
Originally Posted by Nealtw View Post
You are not worried about sag you are worried about a weak spot that can break under a lesser load than it should.
When you load a joist and it sags a little the top is under compression and the bottom is under tension. When you have a notch it may just bend at the notch instead of sagging and that is when it breaks .

Anything you can do to replace that tension area will work Even 2x4 on flat glued and screwed to the bottom of the joist to make an upside down T will do it.
Engineers were usually happy with 3 or 4 feet of 3/4 plywood or 2x joist nailed and glued to one side. lots of nails.
So would it be better to do the second option, partial sister and finish sister with another 2x8 and use another 2x8 piece on the other side to bolt them together? Or would I be alright with just doing the partial sister?
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Old 09-12-2017, 02:40 PM   #4
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Re: Repairing a Notched Floor Joist


I would just do a partial on one side with lots of glue and nails.
Bolting would only be done in the center so as not to weaken the joist. the center is not where you need to add strength.
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