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Tiling Over An Old Concrete Floor

Question:


Is it acceptable practice to lay ceramic tile on a concrete floor? Any problems if the floor is already painted? Is moisture a concern?

Thanks,
Jim

 

Reply:


I'm not aware of moisture being any concern, if the tile is installed properly.

According to the book "Setting Tile" by Michael Byrne (Taunton Press), tile can be laid over concrete floor slabs, but...

  • The tile may crack if any existing cracks in the slab decide to move, which is pretty likely. 
  • The paint will prevent mortar from sticking to the floor.
  • Not if the slab was smoothed with a steel trowel. Most indoor slabs ARE finished with a steel trowel. This makes the surface too slick, not rough enough. He says that such a slab can be roughened up with an abrasive wheel or a special brush-hammering tool. I think he's referring to a device called a needle gun, needle-scaler, or something like that. I've seen them, they have a bunch of hardened steel pins that vibrate in and out, and when you push the pins onto a surface (such as rusted metal, the primary purpose of this tool) the vibrating needles poke away at the finish.

Personally, I wouldn't try applying tile over old painted concrete. These needle gun machines are expensive and could take a long time. Maybe this would be a worthwhile approach if a subcontractor could be found that has special equipment to remove the old floor paint and roughen up the surface.

I would consider securing 1/2" Durock cement backerboard to the concrete, using a Ramset. You can get a small Ramset for about $20 at Sears and for about $75 you can get the trigger-activated Ramset (preferred) that makes short work out of nailing into concrete. These tools use .22 caliber shells to drive hardened nails into concrete, and they work fast. I've never used one, but I've seen them. Also, Hilti makes some professional-grade concrete nailers. Call around. You should be able to rent these tools. I would want to try a small section just to be sure that the nails will go in right and not protrude. The nail length and size of the cartridge are quite critical... not enough powder in the shell and the nails won't go in. Maybe you can ask some tool rental dealers if they have any experience with fastening cement backerboard to concrete.

The other option would be to drill holes and drive Tapcon concrete screws into the floor to hold the Durock. This approach sounds like a bunch of work, and you'll need a hammer drill.

Whatever you do, tile will be cold unless you install a floor warming system. Vinyl looks awfully good from my vantage point. I recently worked in a new house that had what I thought was a nice tile floor, but it was vinyl. It had a rough texture just like tile. I don't know what brand it was. Good vinyl lasts a long time, is easy on the feet, and is much warmer. As much as I personally loathe vinyl products, I must admit that it makes sense for some places.


Bruce W. Maki, Editor.

 

 

 


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Compiled May 12, 2002