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what is Substrate?


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  • what is Substrate?

    testing the "there are no stupid questions"

    I see the word used a lot, and am getting ready to install tile on a newly repaired, leveled floor

    Last edited by pbc; 06-09-2008, 11:16 AM.

  • #2
    The "substrate" is what you use directly beneath your tile. Usually some type of cement backer board.


    • #3
      Yep, you need to add 1/4" backer board to that floor before you tile, make sure you trowel some mortar or tile glue onto the ply then lay your backer board and screw it down ( some say you can nail it down with roofing nails if you use mortar in between.
      I never do, I always screw it down.
      Little about a lot and a lot about a little.
      Every day is a learning day.


      • #4
        In my bathroom, the grout is breaking out of the floor tiles. I have cleaned out all of the old grout and put down new grout. With in 2 weeks the grout was cracking again. when I was cleaning it out I noticed the tile was laid on top of plywood, no backer board. Is this why it is cracking?, Do I now need to take it all up and put down backer? Or could it be the floor is saging when we walk on it ?Joists are 2x8 @ 16'' centers,not sure how thick the plywood is, I wouldn't think the floor would sag or flex. But I don't want to go to all the work and have the grout crack again.


        • #5
          Don't bother going to the trouble of grouting again. It'll just crack again.

          Your problem could be that the tiles are loose, the plywood is too thin, or the floor joists are not strong enough. Or it could be any combination of the three.

          I'd start with the floor joists and determine the distance that they span with no support from underneath. Provided they are pine or fir, the maximum distance they should span would be 11 feet.

          If the joists are okay, then move on to the plywood. The minimum thickness of the plywood for a direct bond application is 1 1/8". There are other standards that apply, including type of thinset, screw schedule, a double layer of plywood, and the grade of plywood. Cutting corners in any of these areas is risking failure. It's also the reason I never do a direct bond.

          Spend a few extra dollars and install an uncoupling membrane or cement board. It's well worth the money. You can get by with as little as 5/8" plywood (although I prefer 3/4") and 1/4" cement board, or if you're trying to save some height you can substitute Ditra for the cement board. Ditra is very user-friendly and adds only 1/8" height to the floor.

          *Note - This is ceramic tile you have on the floor, and not a natural stone like marble, slate, or granite, right?


          • #6
            Even with a floor that has some moderate flex the 1/4" backer board will cure any movement problems associated to loose tiles, either backer board or Schluter matting. In basic terms what either of these products do is the tile sticks to the mat/backerboard the mat/backerboard sticks to the flooring material (substrate) when/if the substrate moves it cracks the bond between mat/backerboard and the tiles remain holding tight to the mat/backerboard. Like putting a stick it note onto the back of your hand, then placing both hands palms together and rubbing them together.

            I've heard some people say that you can lay tiles onto wood sub floors, and you can, you can do anything you want, but will it last ? (no)
            Little about a lot and a lot about a little.
            Every day is a learning day.


            • #7
              Joists are 2x8 @ 16'' centers , span is 10 ft, plywood is 2 @ 1/2 '' thick, glued and screwed. Tile is ceramic.
              It looks like my task is to rip up the tile and put down backer. If so what is the best way to get the tile up without damaging them. or should I just get new tile? Trying not to spend to much $ here of cource.


              • #8
                a lot depends on how the quickset was mixed. too thin and the tiles pop up. too thick and you won't be able to chisel the mortar off the tile. that tool they advertise on tv, the FEIN zip tool may be a help with the vibrating scraper blade. finish up with the carbide smoothing tool. the zip tool MAY vibrate the tiles off the floor. New tiles as an option is your call along with your budget.


                • #9
                  Ok, Thanx guys
                  Looks like I'll try to save the tiles, its not a big space if I can't clean them up I'll get new ones.
                  With all the projects I have done here it won't be long now and I'll be a master just like you . LOL


                  • #10

                    Substrate are cement backer board which is used beneath the tiles...