I am replacing water damaged floor boards in my bathroom. They were previously tiled and I will be tiling them again. It's an apartment and below the floor is concrete, with joists between the concrete and the boards.

The joists are 45x90mm which I am struggling to find. Is this not a normal size?

Also the joists have a black foam tape on the bottom about 10mm thick which I am also struggling to find.

The joists are not attached to anything and are resting on the floor, held together by the nailed floor boards, which I thought was unusual

The apartment is purpose build and around 10 years old

  • 45 x 90 is about 1 3/4 x 3 1/2" - about the real size of a 2 x 4. – Phil G Aug 5 '19 at 18:57
  • It does seem kind of strange. Are the joists water damaged? Is this "structural" or "cosmetic" water damage? Can you post some pictures? – Greg Nickoloff Aug 6 '19 at 17:29
  • I eventually found 'Scapa 3259' which comes in many sizes and was fine for the job – Mark Tickner Aug 28 '19 at 18:39
  • 2
    I’m voting to close this question because it's been abandoned – FreeMan Dec 29 '20 at 17:17
  • @FreeMan I'm not sure why it matters considering it's over a year old, but regardless you can see that I responded to the below answer in the comments – Mark Tickner Dec 30 '20 at 18:18

I'm assuming the "joists" are water damaged too or you wouldn't be looking for new ones. The size you mentioned is close to a 2x4. The foam tape it probably heavy weather stripping used as a cushion to your floating floor. If you can't find the exact size you might want to just replace the whole floor since you'll be tiling it over or use 2x4's and shim the difference.

  • 1
    Since they are giving metric dimensions the may not have inch lumber available (this site is world wide). I would probably sister something close to span the damaged area. – Ed Beal Aug 6 '19 at 19:00
  • I keep forgetting that... I'm in Florida, U.S.A. – JACK Aug 6 '19 at 19:13
  • Yes, only metric is readily available for me, and in the end I found 1mm shorter joists so fitted 1mm thicker foam tape – Mark Tickner Aug 28 '19 at 18:38

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