The original 2x4 that rested on the floor was removed in one piece with approx. 7" of the vertical studs attached to it. The sides of the studs rest against a concrete block wall. The removal was done to allow access to the cold joint for the application of a waterproofing material whose surface is varied and uneven. Now I'd like to install a new 2x4, hopefully with closely matching 7" studs attached to it to be sistered in, since all the original studs were partly rotted from flooding. I can't drill down into the concrete floor because it would disturb the waterproofing, but need something to serve as "shims." I'm concerned about using construction adhesive of some kind since I think I need more time to do the fitting even if I check everything first.


If I'm interpreting correctly, your framing isn't so much structural as a place to hang drywall/ whatever. If this is the case, then a bunch of construction adhesive will do fine. If you can, add an "L" bracket or two to the wall to tie it all together.

Pressure treated wood is probably what your AHJ would call for in this setting.

  • The framing is a structural piece to the extent that the set of stairs removed to gain access to the framed area was nailed into the studs approx. 4' up from the concrete floor with galvanized finishing nails. I'm hoping for a really good fit, since I don't expect to be able to attach the studs to the concrete block wall behind it. The stairs stringer on the other side was attached with some kind of masonry fasteners, since there are no studs there, just the concrete block wall. One nightmare at a time...
    – Carol
    Oct 12 '15 at 15:04

The way I'm picturing your question is that you are trying to level a 2 x 4 floor joist; specifically the one that runs parallel to the block wall. On it will rest the studs that make up the framing for the finished wall? If this is the case to shim the joist level with the other floor joists purchase plastic shims at any lumber yard or home center. Just like wood shims, but won't rot or swell from moisture and the serrations make them easy to snap. Another material for shimming damp environments are roof shingles. Lastly, to splice in stud sections to replace the pieces that were cut out, sister in the new piece and screw gusset plates of the same dimension to either side of the new section.

  • The 2 x 4 rests on the concrete floor and was previously hidden by a 6-step finished stair unit. There are no other floor joists to level the 2 x 4 to. I don't know if the one that was removed had been attached to the floor since the waterproofing work hides that area, but I'm assuming the fit should be really solid. The surface it will rest on is very irregular and I think I need something that would fill it. Maybe applying a slow-drying mortar of some kind and then pressing the new 2 x 4 "unit" into place would work (?). I'm thinking I could force more mortar under the 2 x 4 after that.
    – Carol
    Oct 12 '15 at 15:17
  • sorry I misunderstood the question. You could mix a dry batch of concrete to use as a way to support the 2 x 4. Add enough water to the mix so that when you squeeze a handful tightly no water presses out and it remains compact in a ball form. Mix enough to support the full length of the 2 x 4. Ideally you want to lay out enough so that it can be tamped and compact down to the 2x's final position. If you only need 1" or less use a floor leveling product instead. Construction adhesive, as you noted, would work also.
    – ojait
    Oct 12 '15 at 21:27
  • I'd prefer to use a floor leveling product since the bottom of the stair unit also needs to rest on the floor. The thinkness would probaby be less than .75", although it's difficult for me to determine that. (A door needs to be reinstalled, too, where the floor continues in front of the stairs.) I contacted Kwikrete about using one of their floor levelers and they said there might be a bonding problem with the Xypex. They couldn't vouch for it and said to contact Xypex. I'm waiting...
    – Carol
    Oct 13 '15 at 13:44
  • Well, the waterproofing people said if I use the floor leveling product I mentioned earlier, I should apply a bonding agent first. It seems impractical to me. I wonder if I use some of the waterproofing product and apply it like mortar as ojait described, if that might work, but I'd have to hustle since it sets up quickly. Another suggestion was to install the 2x4s the way they need to be and then fill the gaps beneath the sole plate with spray foam. I think it would be easier, but doesn't sound as solid.
    – Carol
    Oct 14 '15 at 19:03
  • Yes, bonding agents will allow the mortar to adhere better, but if not used it won't destroy the project. As far as a leveling material maybe (and I'm saying this as an un- associated observer, it's being Over thought? Maybe (since it's not a piano that's being built) stay with the tried and most often used materials for the task at hand (i.e. plastic shims, roof shingles , globs of construction adhesives). Consider the doing the project as best as you can, but also how important it is to do it right.
    – ojait
    Oct 14 '15 at 22:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.