No, you cannot put cement board down on a cement slab. They are not meant to be merely bandaids to cover up something. Cement boards need to be screwed or nailed in place over a bed of thinset that takes up the voids under the board, Trying to countersink a tapcon in a cement board will cut right through the board. You would need about 70 screws per board.

while you can not isntall a cement backer unit over a cenemnt floor, you may be able to use use a cleavage, uncoupling, load distribution, and vapor management membrane such as schluter ditra. It is a little more exensive than cbu's but when compared top the cost of asbestos abatement, its a no brainer.

here is some more information:

http://flooringworld.org/floorsearch.php?query=schluter+ditra

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The right way and the wrong way.

Do it right everytime.

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http://flooringworld.org/

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