Does my Floor have to be Level to Install Tile?

by Roger

Before installing tile on your floor you must make sure your floor is properly prepared.  A properly prepared floor does not have to be level. It must, however, be flat.

The only time the levelness (is that a word?) must be taken into consideration is when drainage is an issue, such as on a porch or in a shower. In those cases you must make sure your floor is not level – it has to be angled toward a drainage area.

If your floor will not be subjected to water regularly, such as a kitchen or bathroom floor, it does not necessarily have to be level. That does not mean you can have a 45 degree angle from your door to the cabinet (although I suppose you could if you wanted), it just means if your floor is not absolutely level it will not negatively affect your tile installation.

One of the things you must make sure of, among other things, is that your floor is flat. If it is not it will be difficult to set your tiles without what we call “lippage”. That’s a ridiculous word, isn’t it? Lippage simply describes the difference in the height of two adjacent tiles. If you have a tile that sticks up higher than the tile next to it you have lippage. You don’t want that. Starting with a flat floor helps prevent it.

When prepping your floor for tile trade your level for a straight edge. Don’t be concerned with how level your floor is, be concerned with how flat it is.

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Mimi

Hi Roger,
I want to put little porcelain tile on the floor in my bathroom The house is 1860 and has original pine boards over true 2 x 8 joists. The spacing on those is random 14 to 18 inches on center. The ceiling in room below is partially down is how I know this. The floor over all is not bouncy though one or 2 boards have a spot that has some give.

I don’t want to remove the tub to put in the floor. We have removed the toilet and replaced the floor around it with 3/4″ plywood, shimmed to be flush with existing floor.

My question is how much plywood do I need to put down before the backer board. A guy at home depot said 2 layers, I forget what thickness and wanted the first layer glued to the floor boards. My husband doesn’t like raising the floor that much, but I don’t want cracks in the tile floor. Or do think tile shouldn’t be used in this situation.

Thanks,
Mimi

Reply

Christopher Eshleman

Hi Mimi,

Ok, the first thing is this: you don’t need backerboard on the floor. Or at least, I’ve never heard of anyone using it there. You just need a nice, solid wood substrate on which your tile will sit. If your subfloor is moving, your tile will crack. Period. Now that’s for large tile. If you’re using small mosaic tiles, it’s not the tile but the grout that will crack and fall away, leaving you with gaps that water can penetrate into and cause problems, not to mention the eyesore of missing grout lines.

What you need to do is to screw (or nail, but I like screwing, no pun intended) all those pine boards down into the floor joists. If you simply glue plywood onto moving floor boards, the plywood is going to move too. So you need to secure those first and then put your plywood on top of your nice, solid floor boards. If you don’t want to remove the tub to screw the floor boards underneath it, you can always shim them from below, but that’s a pain in the butt and I don’t recommend it, since it’s not as stable. Though, of course, if there’s no give around the tub, it might not be necessary. I say it’s better to be safe and do the job right. I’m not sure what the exact situation is, but if it’s a stand alone tub, taking it out shouldn’t be too difficult, or just move it to the side so you can get underneath it.

And one layer of 3/4″ plywood is definitely enough. That, along with your securely fastened pine floor boards, will be a nice and solid substrate for your tiles.

Hope that helps.

-Christopher

Reply

Jared Duplantis

Hi, I’m wanting to lay ceramic tile from my kitchen into my living room however. The cement slab where the kitchen and living room meet are different hieghts. About 3/8″ to 1/2″ difference. The living room was an add on so the slab wasn’t poured at the same time. What can I do? Also, considering staining the living room maybe. Thanks :censored:

Reply

Christopher Eshleman

Hi Jared,

The simplest thing to do is just to put a room dividing metal trim between the two rooms. I’m not sure what the technical term for it is, but it’s meant to be used for exactly this situation.

The more complicated thing to do is to even out the two floors with leveling cement, but there is A LOT of work involved in doing that, as you need to prepare the existing floor to make sure the new cement will adhere to it, and having such a thin layer of cement isn’t very sturdy, so I would probably just go with the metal trim solution. There are actually several different kinds you can get, so you can choose whichever one suits you.

Hope that helps,

-Christopher

Reply

Nate

I have a bathroom floor in a basement we are finishing. The floor concrete and we have poured self-leveler over it to deal with a small peak at a seam. Can I tile directly over the self leveler, or do I need to put something like DITRA down over the self-leveler first? (The room is 5×7)

Reply

Roger

Hi Nate,

You can tile directly to the slc.

Reply

Rick

What is the best method to obtain a flat subfloor. The subfloor is 5/8″ plywood and there are a couple low spots, about 1/8″ to 1/4″ max. I believe the knuckleheads who built the house put a couple joists crown down. Shingles and roof felt followed by 3/8″ plywood followed by 1/4″ durock; or 3/8″ plywood followed by 1/4″ durock and then the low spots filled in with SLC? Thanks for your help.

Reply

Roger

Hi Rick,

No shingles or roofing felt. The ply, durock with slc over it (thinset beneath the durock) will work just fine.

Reply

Kathleen A Ferraro

The contractor who replaced the tile in our bathroom after it was damaged by water and chemicals used to put out a fire wrote in his insurance proposal that they would remove and replace 1/2 inch cement board and 3/4 inch BC plywood. The bathroom had been installed in 2002, and we had had no problems with the tile or grout until the fire. The height difference between the tile floor and the wood floor in the bedroom was less than 1/4 inch. We indicated we wanted it to be restored to its pre-fire condition.

The new floor is about an inch higher than the original one. The contractor cut the bottom of the door to fit. The door is now 3/4 inch shorter and there is barely 1/4 inch between the bottom of the door and the floor. In addition the floor feels kind of lumpy underfoot. I am also concerned that the height difference might create problems with our curbless shower.

The wall tile job is also terrible. I have not paid the contractor’s final payment and don’t plan to. My guess is the contractor did not replace the old cement board and plywood before installing the new floor, but could something else have caused the height difference? I can send photos.

Reply

Roger

Hi Kathleen,

I think you’re probably correct. That’s a huge height difference. He likely just went right over what was already there.

Reply

Kathleen A Ferraro

Thanks, Roger. A floor inspector came today and was able to look below the new plywood and found it had been installed over the old subfloor. The contract says remove and replace subfloor, so I believe this is a breach. The inspector also said the floor is moving and has bumps in it. I am waiting for his report on the floor and the wall tile and plan to send the contractor a letter saying I will not pay until he fixes the problems with the floor and also the poor workmanship with the wall.

Reply

angel barros

Hi, First I want to congratulate you for keeping this page, it helps a lot to installers like me.
I have a project of 4500 sf on a second floor. the substrate its a lightweight concrete over wood beams, and needs a lot of prep. i’m planing on patching cracks and then self leveling the floor and install a ditra underlayment and then lay tile with 12″x24″
My questions is, if the lightweight concrete its going to support the weigh of the tile, I’m worrying about doing a good installation that can fails in a year with a bunch o crack tiles or worst.

Reply

Roger

Hi Angel,

If you are talking about gypcrete – yes, it’ll support it just fine. Be sure to use the primer for the slc to ensure a proper bond to the gypcrete.

Reply

Albert

I live on the second floor in a condominium. I am replacing the marble tiles with 24″X24″ rectified polished Porcelain tiles. The existing area has plywood sub floor with 3/4” concrete over. I am tiling the foyer, kitchen and the powder room. The floor slopes down from the entry door toward the kitchen of about 1”. I am confused of how to tile the area with the existing condition. Does my floor have to be level to install tile? Some installers have suggested to remove the concrete and use Hardie Backboard for tiling. Others have different way of leveling the area which is to use paper on plywood, pour cement mortar and thinset and then tiles. I am really confused. What is the correct way of handling this project? I appreciate your help?

Reply

Roger

Hi Albert,

The best solution is self-leveling cement. I highly doubt it’s actual concrete, it’s likely gypcrete (lightweight concrete). Your floor does not need to be level, but it does need to be flat.

Reply

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