After removing an old bathroom floor in a historic structure, in order to sister joists for a level surface to install new subfloor, we found that one of the original floor joists was notched, and then cut, by previous owner in order to run drains. We're redoing all of the plumbing, but this is a question about the joist.

How would we fix this? You'll see in my pics that previous owner/worker tried to brace this between two joists with a 2x4. I don't trust it.

How would you fix this the right way?

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  • It's not clear from your photos what the options are. is it possible to slide a new joist into place from the end opposite the foundation?
    – isherwood
    Commented Jan 5, 2017 at 16:48
  • How far back does the joist go?
    – mmathis
    Commented Jan 5, 2017 at 16:50

1 Answer 1


You really need an engineer to give you an answer and sign off on this. But, being this is the internet, here's my $0.02 anyway.

Your best bet is to replace the whole joist if feasible and not to disruptive to the rest of the structure. But it will be very disruptive to the rest of the structure & flooring and probably impossible to get it into those foundation pockets on both sides. So...

I would cut the existing joist back to the middle of that knee wall or 2x4 nearest the foundation wall. Not counting on that structurally, but you need to square off the end of the existing joist and it makes a convenient place to put the end of the new joist while you tie things together. Take off that little bit of 2x4 back near the drain pipe.

Then I would slide a new piece of joist into the pocket in the foundation wall and flush with the end of the existing joist on top of that 2x4.

Then I would sister the joist on both sides with 2x dimensional lumber of the same height as the existing joist from the foundation wall pocket back to at least 2' to 3' past the end of that huge notch. Be generous with construction adhesive, then clamp the whole thing up and put a few bolts through to pull it together and nail it along the length.

  • 1
    All that ^^^. But do I see a sliver of light at the next joist pocket? Could you pop a bit of siding off and sneak a new (long) joist from the outside? Commented Jan 5, 2017 at 17:15
  • Good eye - I didn't notice that. Opens up options for replacing the whole joist. Commented Jan 5, 2017 at 17:16
  • Ah. Sliver of light is the end of a carriage bolt from the new wood we've sistered in.
    – mctossy
    Commented Jan 5, 2017 at 17:57
  • Ok - obvious now that you mention it. Commented Jan 5, 2017 at 22:19
  • Thank you for the detailed answer, CoAstroGeek. Would you use an angle grinder to expand that notch in foundation wall in order to accommodate for the new lumber now that we're using one piece on either side?
    – mctossy
    Commented Jan 6, 2017 at 23:45

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