Tile over concrete in basement.

Discussion in 'Ceramic and Stone Q&A' started by mvaughn88, Dec 5, 2017.

  1. mvaughn88

    mvaughn88 Member

    Getting ready to install plank style tiles over concrete below grade. It will be alternating rows of 6 and 8 inch tiles. Concrete is just over a year old, clean, dry and no moisture issues we have seen. I plan on filling the cut seams with silicon, but is there anything else I need to know? Do I need to seal the floor, use self leveler, or a certain type of mortar?
  2. Jim McClain

    Jim McClain Owner/Founder Administrator

    Cut seams in what? You posted in the ceramic & stone section; there are no seams in ceramic or stone.
  3. mvaughn88

    mvaughn88 Member

    sorry about that. I was referring to the seams that were cut into the concrete floor by the builder of the home.
  4. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    Put a few drops of water on slab, see if it soaks in or beads on top to know if they used a curing agent.

    The control joints need a crack suppression membrane like Redgard liquid. Three tile wide.
  5. mvaughn88

    mvaughn88 Member

    Do I need self leveling compound after that?
  6. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    No silicone for joints, just the liquid crack sup membrane and all random cracks treated similarly like the control joints.

    You didn’t say it wasn’t flat. But the proper self leveler goes first if needed, control joints must be transferred and not covered or at least re cut where pre existing joints are. Then the membrane.

    You have pictures prior to concrete going down (the vapor barrier view)
  7. mvaughn88

    mvaughn88 Member

    not sure hoe out of flat it is. There are no drains in the area where tile will be going, just going on the assumption that the builder pitched the floor and by the differences in gaps in the drywall on the newly framed walls.

    and I will check on pics, this is my nephew's house.
    Last edited by a moderator: Dec 5, 2017
  8. mvaughn88

    mvaughn88 Member

    Ok, check the floor and it's level at most spots, just have a few spots that are 1/16 slope. No pics but confirmed there is a plastic vapor barrier between the gravel base and the concrete. With that in mind can I just use the Redgaurd to fill the expansion seams?
  9. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    When thinset is used to bond ceramic to slab they then become one. Tile being 1/2” thick versus a 4” slab moving snaps a tile like a twig when slab expands and contracts, and moves. A crack suppression membrane isolates that minor movement and bridges across several tile. The cement grout also does not flex, it cures rigid. That is where a flexible grout colored caulk is used.

    The width of plank is easy for the three wide tile principle, the length so far I’ve seen standard max around 48” I’m not current on those recommendations, but basically when they were 24” long I would zigzag across the width of random patterns to stay close to right over the control joint with the flexible caulk.

    You’re theory on putting silicone into the joint is wrong unless water was gushing. Moisture will travel through the concrete if there is a breach in moisture vapor barrier.
  10. mvaughn88

    mvaughn88 Member

    So if I understand.

    I'm using 6 x 24 and 8 x 48 tile. It will be a row of 6,8,6,8, etc. to simulate wood plank flooring. I need to use the Redgard liquid you suggested, but still not sure if only over the expansion crack in the floor to 3 tile wide, or the entire floor. I see you suggest flexible grout, is there a certain thinset I should look for?
  11. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    Usually now called “large format tile thinset”. Brand doesn’t matter. The “soft joint” is the caulk only for above control joints, the rest is usually Portland based grout or costlier urethane Or acrylic blends.
  12. mvaughn88

    mvaughn88 Member

    Thanks for all the help.
  13. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

  14. mvaughn88

    mvaughn88 Member

    OK, this coming Monday is finally the day to start. I understand the layout and the starting point using the plank tiles. The only thing I'm not clear on is if we can just thinset right over the concrete without using roll membrane?
  15. kwfloors

    kwfloors Fuzz on the brain Charter Member I Support TFP Senior Member

  16. Kman

    Kman Tile Expert I Support TFP Senior Member Published

    It's important to know if they are control joints or expansion (or construction) joints. Control joints can be tiled over by relocating them in the tile surface. Expansion joints cannot, at least not without honoring the joint through the tile above it.
    • Agree Agree x 1

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