kathywaters

We took out our old ceramic tile floor in the kitchen and hall. It was in 2-3" of mud. Now we are down to the original plywood floor which is not level, soft in spots and high where some panels join each other. What do we do?
Do we use self leveling cement and then put down 1/4 or 1/2 hardiback?
Do we put down 3/4 " new plywood over the old, then 1/4 " hardiback?
Do we need to pull up the original plywood and install new subfloor?
HELP!!!

Also when putting down new plywood do we lay it over the joints on the old plywood or match up the joints?

Daryl

Sounds like some of the original subfloor is warped thus giving the high spots and soft spots. Personally I would replace the original subflloor. By doing so you remove the damage as to cover it up. Adding another layer of 3/4" plywood plus 1/4" hardi backer will raise your floor at least 1 3/8 " with floor tile and thinset. Big problem at exterior doors and cabinets, dishwasher etc. However you have stated you removed 2-3" of mud base and tile, so even after repairing the original you might have to add a second layer for the added height needed. If you put a second layer over the original without repairing it you could still end up with soft spots and low spots to deal with that will give under the rest of the materials thus possibly causing cracking of tile.

glennjanie

A hearty Welcome to the Fourm, Kathy Waters:
In order to get that thick bed of mud the original guys probably had to cut several joists down. Therefore, I recommend that you remove the old subfloor and consider sistering some new joists in there, which will bring you back up to a level you can work with. Then you can use the new 3/4" underlayment grade, tounge and groove OSB; add the hardi board and finish it off however you started.
I have some of those 'cut-down' joists in my house for the mud bed and they are resting on 4 X 6s and basement jacks right now.
Please post back and tell us how you get along, maybe even some pictures.
Glenn

kathywaters

Thank you for the reply. We have gutted the kitchen as well so I do not have to worry about additional height. I have some room to work with since the mud floor was so thick. The house is 20 years old and I believe they laid the original plywood knowing that they were putting in a mud floor and did not worry about having a level subfloor. I do not believe the plywood is warped - it was just installed unevenly but some spots approximate 6" around are soft.

Mary Jo

You got some great advice...one addition...DON'T match up joints. Always off set your seams for better stability!! Just finished a similar project and it's wonderful to do it right and know your set for many years!!

kathywaters

Thought I would give an update. It was going to be a tremendous amount of work to pull up the original plywood. We decided to put down 1/2" CDX plywood. We did put it off the seams of the underlying plywood. That did take care of the softspots and made the floor feel much firmer. We are now putting down thinset (thicker in some spots to help with the leveling)and screwing down 1/2" hardiback leaving 1/8" between boards. The manufacturer recommends laying down tape between the joints and then putting the thinset over this when doing the tiles. Question: Is the tape necessary?
After putting the hardiback it was suggested by the manufacturer to use self leveler to help with the problem of high and low areas. Is this easy to use or are we better off trying to put thicker thinset in areas that are low? We are off by 1/2" in some areas. Thanks for all the help.

TileGuy

Tape is necessary and god forbid you have a problem in the future the warranty wont be void because you didnt use it.

As far as self lveling areas:
No its not hard at all. Just remember to wipe the hardie backer SPOTLESS of dust and wipe it with a damp sponge just before using the leveler.

As far as floating the tile as you go:
I wouldnt suggest it unless youve done it before. I would suggest using the leveler and getting it as close as possible. You can take care of the rest as you tile it.

cibula11

Some leveling compounds need to have a primer put on the surface first. The cheap kind definately could use a primer on the floor, but the expensive stuff seems to adhere better.