# Is it bad to use mortar to level a floor?



## CB2007 (Jan 27, 2007)

We are about to put down the backerboard in our bathroom so that we can eventually put the new tile on top of that, however our floors are not completely level. The floor height varies +/- 1/8" (1/4 at the extremes). We know we need to level the floor below placing the backer board on it, because the last thing we want is for the backerboard to flex and ultimately cause cracks. Would it be bad to just use normal mortar to level out the floor (the same mortar we were going to use to afix the backer to the floor before screwing it in? We'd like to just use mortar if possible, and have the mortar slightly 'deeper' in some areas. We do have some 'self leveling' compoud, but to be honest.. it makes us nervous. We're afraid that since it's so liquidy, that it will find a crack somewhere and run down under the floor and onto the ceiling downstairs. HELP! * Also, is there a 'max' depth for the mortar?


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## troubleseeker (Sep 25, 2006)

CB2007 said:


> We are about to put down the backerboard in our bathroom so that we can eventually put the new tile on top of that, however our floors are not completely level. The floor height varies +/- 1/8" (1/4 at the extremes). We know we need to level the floor below placing the backer board on it, because the last thing we want is for the backerboard to flex and ultimately cause cracks. Would it be bad to just use normal mortar to level out the floor (the same mortar we were going to use to afix the backer to the floor before screwing it in? We'd like to just use mortar if possible, and have the mortar slightly 'deeper' in some areas. We do have some 'self leveling' compoud, but to be honest.. it makes us nervous. We're afraid that since it's so liquidy, that it will find a crack somewhere and run down under the floor and onto the ceiling downstairs. HELP! * Also, is there a 'max' depth for the mortar?


Do not use mortar, use floor patch. This is not the same as self leveling and is screeded or troweled into the low spots to fill them. Your concern about self leveling is justified, if mixed thin enough to flow properly, it will find any crack or opening to run through.Also, do not use regular mortar to bed the backer board, use thin set. Talk to your tile supplier, he will give you the correct products.


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## mdlbldrmatt135 (May 31, 2006)

My Parts had a floor in a 200 yr old house that need "flatened" the middle was almost 2" lower than the edges (Jacking wasn't an option) so we use Mortar to level it. It's been 3 years with a floating floor over it and No problems to speak of.


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## Bud Cline (Mar 12, 2006)

You cannot use a patching product to "plane/flatten" the floor then install cement board over that. You need the cement board installed first in a bed of fresh thinset THEN after the cement board is contoured to the subfloor you can plane the surface from there.

Overall Self Levelling Compound would be the path of least resistance. It's a great product but requires some attention to detail. To discourage the use of SLC is a sign of inexperience.

Floating floors have nothing to do with this project and shouldn't even be in the conversation.


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## brian mc tigue (Oct 1, 2008)

*do you have answer to question below*



CB2007 said:


> We are about to put down the backerboard in our bathroom so that we can eventually put the new tile on top of that, however our floors are not completely level. The floor height varies +/- 1/8" (1/4 at the extremes). We know we need to level the floor below placing the backer board on it, because the last thing we want is for the backerboard to flex and ultimately cause cracks. Would it be bad to just use normal mortar to level out the floor (the same mortar we were going to use to afix the backer to the floor before screwing it in? We'd like to just use mortar if possible, and have the mortar slightly 'deeper' in some areas. We do have some 'self leveling' compoud, but to be honest.. it makes us nervous. We're afraid that since it's so liquidy, that it will find a crack somewhere and run down under the floor and onto the ceiling downstairs. HELP! * Also, is there a 'max' depth for the mortar?


:thumbsup:


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