Can I install Concrete backer board over old deteriorated concrete?

Question

The concrete in the laundry room is old (over 55yrs) and has been crumbling and dusting.  The concrete is in OK shape, does not have water problem, is very dry, but is poor in strength.  The concrete in another area was really hard!.  We are in a freeze/thaw zone, although the basement is heated.  

We have hammered most of the loose stuff away, and vacuumed the loose dust.
Now I want to finish with ceramic tile.

We will level the concrete floor with a modified polymer thin-set concrete.

To prep/finish the laundry room floor with tile:
Should we install a modified mortar + tile?
Or
Should we install modified Mortar + Cement Backer Board + modified Mortar + Tile?

Thanks!

rob s · Accepted Answer

What you really need to do is completely clean the floor .  More than you already have, and pour a self leveling compound over  that.. You will need no additive when pouring over concrete.   The reason you have to do it this way is for 2 reasons. One is that modified thin set when applied to deep dosn t have the compression strength to properly work.  And second it is difficult and almost impossible to properly attach a cement board to a slab.
  Any questions you can e mail me through my avatar and check my qualifications there.  GL

Walter shumate · Answer

I'm no tile man but I would get some self leveling concrete and a bonding agent that will help it bond to the existing concrete  and then you could go about the normal process with a lot less time and a huge $ savings . Good Luck WS

Can I install Concrete backer board over old deteriorated concrete?

2 Answers