I’m doing renovations in an old kitchen. I removed the ceiling as it was damaged, old and nasty. I found that when some prior owner renovated the bath above, they cut into the joists to add plumbing. The cuts are minor to cut right through in places. They did a poor job of attempting to scab a 3 foot section of 2x8 for support on one joist (the cut through one) and nothing on the other 3 joists. ( I guess I shouldnt worry, they only installed a large tub above the 4 joists they compromised!!!!)

The joists are 2” x 8” x 18” long (a full 2”x 8”, not 1.5” x 7.5”). The cuts are about 1 foot from the wall.

Four joists have been compromised.

What I am looking for is a solution to re-support them.

My initial thought was to build a header that would run below the 4 joists that would be supported by two studs on each end (there is a door in the wall below this point, so I couldn’t have studs all along the header). I’d prefer not to do this solution as the header would cause problems with cupboards.

My other thought was to remove the plumbing, scab 6 foot lengths of 2x8 to the existing joists using bolts then add the plumbing back in. I’d still have a concern with this as 4-5 inch holes would still be needed for the toilet drain. What if I were to scab 2 2x8s on each side of the joist?

Other options?

Hopefully the pictures below will help show the situation.

Any thoughts would be appreciated. (The wiring will be removed and done right!)

Below View

Distant view


  • Looks like there is space to move the pipe back behind the wall allowing all studs to be rebuilt. The trap looks like it will do nothing as it is and probably needs rebuilding
    – Chris
    Mar 14, 2021 at 14:31
  • why do you think the trap is doing nothing? it looks like the critical trap length is fine for the weir. Mar 14, 2021 at 18:07
  • are the 18' joists spanning 18' unsupported? only the ends of the joists are supported? Mar 14, 2021 at 18:12
  • 1
    Oh first picture is a ceiling shot my bad, thought it was a wall shot by mistake which is why the trap looked weird to me
    – Chris
    Mar 15, 2021 at 4:19

1 Answer 1


The typical thing to do here would be to cut the joist that has nothing left, double block between the two side joists and sister those two sides joists so they are doubles and pickup the load from the cut joist. The cut joist area then just becomes an opening in the floor structure.

You could certainly build a wall with a header below to support the joist past the cut area. Height of header depends on span and if you are putting a door below it you are limited with door heights.

An structural engineer could probably prescribe something simpler. I had a somewhat similar situation with 18' overspan joists and they were able to prescribe 3/4" ply on each side 18" past each edge of the cut. My joist had a notch at the top but was mid span so the loading and stresses are different than your case.

I wonder if you could do something similar but girdle the joist and have the new joist scabs extend down an additional 3" and block the inside of the girdle. You'd loose 3" of ceiling height for the girdle area but if you are putting up upper cabinets in this area you could probably just custom make the cabinets or have some kind of crown trim detail to hide the lowered portion or if this is a limited room just have the ceiling in this one room slightly lower.

Any solution outside of a support wall or doubling would require a structural engineer.

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