QUESTION

Should I use a Mortar Bed or a Backer Board under the tile - I have torn out my 7'x7' bathroom floor including what i think was a mortar bed - (a very sandy mixture). Now my floor is down to the concrete slab which is too low for me to install my tile. How do I raise or make a new mortar bed to raise my floor up at least 1 1/2"? Do I still need to apply backer board too after this is done or just put the tile directy on the new bed?

ANSWER

ANSWER - The best installation method for your situation is to install a mortar bed over the concrete slab to the correct height so your tile finish is at the correct elevation.  Then thin-set the tile directly to the mortar bed unless you want a waterproof/crack isolation membrane, which then you have to install that first.

There is no need to use a backer board for this type of application.  It is necessary that the installer understands and has experience at installing mortar beds properly.  There are many variables to consider to determine what type of mortar bed and which method to use.  Most important is to understand the condition of the slab and to properly prepare it for the tile application.

To get some guidelines on how the mortar bed and tile should be installed go to our website under FAQ Ceramic Tile and Stone Installations and go to question/answer #45 to download an installation guideline.