Floor leveler over HardiBacker?
I just completed installing 1/4″ HardiBacker over a plywood subfloor in my master bath in preparation for installing 12×12″ porcelain tile. I installed the HardiBacker using modified thinset and roofing nails. I taped and covered the joints with modied thinset. Before installation, I used a beltsander (and sometimes a power planer) to smooth the transition between plywood sheets and also to lower out a few high spots.
The problem is that the floor is still not quite as flat as I think it should be. The high spots are not visible to the eye, however I can feel them a bit as I walk around the floor. I am looking at a floor leveler (Custome LevelQuik Extended Setting) since I am not real speedy. Their installation info mentions covering concrete floors as well as wood and various other surfaces, but not a cement backer board. It seems like it would work just like its use over concrete but I am not certain.
Does anyone have any good or bad experiences in using this stuff over cement backer board?
If OK for use over backer board, would a primer be required (as it is on smooth cement floors)?
Also, any thoughts on the best way to seal around the eges where the backer board meets the bottom edge of the drywall so the leveler doesn’t flow into these gaps? Would any kind of tape work (like duct tape)? The gaps seem way too big to use any kind of caulk. What products do most folks use for this?
As long as I follow the directions as to amount of water versus leveler, is it really self-leveling or will I need to trowel it around a good bit to help it along?
Many thanks to all,
Replies
Self leveling will work great over hardi backer. It flows with a "pancake mixture" type consistency. No primer needed but you may need multiple buckets. you kind of want enough for it all to slef level at the same time, not mutliple small buckets that set up between application.
Tape should work just fine though some people use spray foam (great stuff)
Let us know how you make out?
It will work fine over Hardi but remember it is floor leveler so that s what it will do. If your floor isn't level it may take a lot of expensive product to level the whole floor. A much better choice would be to flatten the floor using a heavier bed of thinset under the tiles.
If you really pay attention...
If you really know your floor. If you really know where your low spots are you can plan your installation so you will remember where to go heavy with the thinset under the tiles in the low spot.
I Tiled a floor once with a massive hump. I first used some floor leveler which brought the sides of teh room up a bit, but the floor still continued to rise into the middle fo the room. I did not think I could level it all out becuase of various room transitions. So I tiled it and when I came to the crown in the room I carefully had a bit more thinset under the tiles on either side of teh crown and then for tiles stratling the crown I went extra thin in the center of the tile so the tile would lay flat. YOU MUSTCHECK EACH TILE in that application to make sure you have 100 % thinset coverage under the tile or you are likely to hav voids and the tile will crack. My install is strong after 18 years.
That said, if you have one or two bird baths .. get the leveler. Leveler will not help you if you have a floor which slopes from one side of the room to the other as in those cases I find your slope is often a total of 1/2 and inch or so. Alot of leveler and will cause problems with door openings, etc.
opps old post
oops
Do it once and do it right
It is a shame that you did not level BEFORE installing Hardi..sigh. And, even though you've set Hardi in thinset, screws rather than nails should have been used.
Plug the gaps near the walls with caulk backer (a rope of foam-like material that comes in several sizes). When leveling is done there should be an expansion joint at each wall.
Unless you are a seasoned pro tile layer, I do no recommend leveling as you set tiles. If you must level with thinset, do it PRIOR TO installing tiles, and let the thinset dry. You want to achieve as level a surface as you can BEFORE tile work begins. Then you apply an even coat of thinset with a notched trowel. Lightly back-butter your 12x12 tile, and lay it.
One important point, for any tiled bathroom: When laying tile around the toilet take great pains to get the floor completely flat under the entire "footprint" of the toilet. This will make it much easier to set the toilet and will help prevent rocking and leaks down the road.
Better to have used the self leveling stuff under the hardibacker but it should stick fine. The self leveling material goes off real fast and it's difficult to feather the edges.