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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, 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 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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