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.
we are planning to tile a small kitchen is a basement suite we are building. there is an old crack in the floor which we plan to fill, and along that crack it has raised a bit so the floor slopes downwards to each corner. The floor is concrete, was covered mostly by linoleum tile glued to the concrete but missing a few tiles here and there. Do you think we can try to just thin set and set the tile right over the lino tile if it is not too unlevel – or best try to remove the old lino first – will the thinset stick to the lino?
and should we consider concrete board if the difference is too great?
Hi Judy,
You can not set tile over that lino, it needs to be removed. You will also need to ensure that the concrete is clean enough to bond to the thinset, splash water on it and make sure it soaks in. If not you’ll need to scarify the surface to open the pores of the concrete. If the crack has vertical displacement (one side is higher than the other) a tile installation WILL NOT last over it, if there is vertical movement you can not tile over it. Concrete board is not suitable for use over concrete – it is only for use over wood substrates.
Roger,
Thanks for sharing all this information on your website. I am tiling our 100 sf laundry room and have some issues with the floor being flat. It primarily appears to be along a crowning joist. I have a sheet of 3/4″ plywood and a second sheet of 1/4″ plywood as subfloor. When I check the flatness with a level along this joist it appears to be off by 3/16″.
Can I simply even this out with thinset and 1/4″ backerboard? Or do I need to apply SLC on top of the backerboard too?
Hi Mike,
You ca do it either way, but the slc is much easier.
Hi Roger,
We have thick, uneven slate tile installed in our kitchen, but it was not installed under our cabinets. This has made it difficult to get the dishwasher I really want, and has also made the counter height shorter than the norm. We are finally ready for new kitchen cabinets and have the opportunity to fix this problem. Most advice I’ve seen says to put down plywood to raise the base cabinets, but since the kitchen is a potentially wet environment, I don’t particularly want plywood under my new cabinets (they now rest on a slab floor). Is there something else I can use to raise the new cabinets to the height of the existing floor that will not soak up water, expand or get moldy when wet? Should I use marine grade plywood?
Hi Ciel,
You should not put wood on concrete, it may warp and cause problems with your cabinets. If you are not installing new tile you can put tile under the cabinets or, if you are replacing the tile just put it under the cabinets as well. You may be able to find adjustable legs to put under your cabinets, but I’ve never seen them.
Hi Roger,
Ok so basically in tears…….We bought 20 x20 tiles for a basement floor. We ”tried” using self- leveling cement to level out the floors but clearly it was not done that well because laid out the tiles (dry) and under certain ones there is still some space- one appears to be almost half an inch. For weeks the person who was going to do the floor said we could fix this with mortar or thin-set and now he is concerned and worried. Is this possible? do we have to ”mud” ( his word) the entire floor or start over with more bags of the slc or will thinset or mortar be good. Want to move in and this is again stalling us. Thanks
Hi Dee,
A medium-bed mortar can be built up to 1/2″ (some of them) to compensate, but thinset can not. Your best bet would be more slc (done correctly, of course). It does not NEED to be mudded, but it’s an option. The amount any medium-bed mortar can be built up will say on the bag.
Thank you for all the information available on your website. I am laying 6″x24″ ceramic wood tile throughout the main level of my home. The 14 year home has OSB over the basement and concrete slab through the rest. The OSB is 1/16″ higher than the slab. We installed cement 1/4″ backerboard with thinset over the basement which includes bathrooms and hallways. I had hoped to lay the tile directly on the concrete slab since most of the settling has already happened. First, can I put the tile directly on the concrete slab or do I need a membrane such as Ditra? Second, what is the best way to resolve the height difference? Third, do I need something special over the joint between the OSB and the slab? Thank you!
Hey Jeremy,
You can install directly to concrete. Your joints need to go right up through the tile and you need a soft joint above them. The height difference can best be dealt with using medium-bed mortar. Yes, you need a transition of some sort between the two substrates, they will expand at different rates. You need to have soft joint over those as well. You can use something like redgard over that transition under the tile.
Thanks for the response. Do you have a good resource that explains the details of using the medium bed mortar to build up to the 1/4″ backerboard? I assume feathering it out over 4-5 ft will work? Do we then need to let it cure before applying the redgard? Then thinset and tile allowing for soft joints, correct?
Medium bed mortar takes the place of regular thinset beneath the tile. It can be built up to 1/2″ whereas thinsets are limited to under 1/4″. Your substrate needs to be prepped before installing the mortar and tile. It would be easier to use kerdi over the concrete, which would bring it up almost to the backer, or using slc over the concrete to make it all level.
You do not want to feather it out. The purpose of the medium bed mortar is to have the entire installation on the same flat plane. i.e. regular height over the backer and 5/16″ under the tile over the concrete to be flush with that.
Yo, Rog…
I’m about to lay some 12″x24″ porcelain tiles in a kitchen. The substrate is 5/8″OSB + 1/2″ plywood screwed and glued (not to joists), joists are 2″x8″ sistered on 12′ span. I will be using Ditra XL as my base. The floor is shaping up nice and solid. The room is 12’x19′, and I do see dips of 1/2″ accross the span of the room in various directions, using a laser level… BUT… if I use my 4′ level, I’m not finding so much in the way of un-flat-ness. So, is there a rule to max variation in flatness over a specific distance to apply?
Cheers!
Hey Perry,
Minimum flatness by standards is no more than 1/4″ variation in ten feet and no more than 1/16″ in one.
Thanks Roger!
I’ve book marked your site… lots of great info here.
Perry
Given your past response on underlayment, I’ll give you an ounce or two of validity
I’ve scoured my 450sq ft, 1/2″ plywood with my 4′ metal level for valleys. Some are small, say 1/8″-1/4″ and I plan to use thinset to deal with those before getting the Ditra down. The hall, bath, and mud room all have quite the issue though, with the center of the walkways rising maybe 3/8″ above the edges. SLC seems needed but I’m nervous because the hall connects to the kitchen which doesn’t need it and if I screw up I’ll have new peaks from the SLC. Maybe I should use medium bed instead…..
Question 1: Can I use a bit more water than indicated to ease feathering/finishing or will that screw up the SLC chemistry? I will use a finishing trowel.
Question 2: All the videos I’ve seen include using SLC on the ENTIRE floor and I REALLY don’t want to do that. Can I avoid that by using it sparingly and just fill valleys or is that unlikely to work? Any tips (linked or written) are appreciated.
Lastly, love the site, you writing style, and your info. Will pickup the book to show support, especially since I have to do a full bath shortly so the complexity rises with the waterproofing factor.
Hey Doug,
1. It may screw up the chemistry. It also may cause it to shrink.
2. If you get an slc that states ‘feather edge’ then you can use it for just the valleys and wherever you need it with no problem. Latilevel.
Hi Roger,
Thanks for such a great site. I have used it as a reference for smaller projects and it has been invaluable in helping me avoid flaming dogs (well, cats in our case).
Our house was built in 1926 and an upstairs bathroom was remuddled twice before we got here. Last fall we start in on a full, rip it all out renovation of that bathroom. The floor joists were WAY out (2″+ across a 12′ x 6′ space)of level so I sistered in 2x10s to the existing 2x12s and then laid 3/4″ advantec over that leaving 1/2″ gap around the edge. The doubled joists are 16″ on center. Did OK but now I have a corner that is high and the whole floor still slopes about 1/2″ down the long dimension. In considering our options we came up with the following plan to prepare for 12″ mosaic squares:
1.) Install a 1/2″ plywood underlayment leaving 1/4″ gaps between sheets and around the edges.
2.) Seal the gaps between plywood with silicone.
3.) Install dams and edging and seal to create a pan in the whole room.
4.) Prime with specified primer for SLC
5.) Pour self leveling compound to bring the whole floor up to the high spot. Worst area will be about 1″ to 1-1/2″ deep.
Our thinking is that this will leave us with a flat, firm surface onto which we can install Ditra. Three questions for you.
1.) Is this the right approach? Don’t mind the work but I want it to be right.
2.) Do we install Ditra directly on the SLC.
3.) We live in a pretty rural area so Lowe’s is the main source of material. I can order through the local lumber yard if needed to get the proper materials. Lowes here lists TEK Skill Set SLC and Laticrete for grout and thinset.
Thanks for any help or suggestions.
John
Hey John,
1. It is absolutely the correct solution – well done! I wish all my readers would be willing to do what’s needed.
2. Yes
3. Tec SLC is good stuff and laticrete is my preferred grout and thinset. You’re good to go!
Thanks so much. I really do want to avoid flaming kitties! Thanks again for a great site.
jph
Hello,
I am tiling a concrete basement floor using 24″ tiles. The concrete floor is in good condition with the exception of a few cracks and a low spot. I am going to use a paint on membrane for the cracks as the concrete is 9 years down and I am not too worried about additional settling.
My concern is about the low spot. The slab has a low spot of about 1/2″, but it is a gradual slope from both sides over about 12′. It is not discernable to the eye, but water definitely puddles in the low area. It is still a flat surface with no protrusions anywhere. My question is, do I need to use levelling compound, or can I just apply the tile staying with the slight slope of the concrete? Any info you can provide would be appreciated.
Thanks, Miles
Hey Miles,
You should use slc to level it out. If there is a low spot then it is not a flat surface – can’t be. The larger the tile you use the flatter your substrate must be. 24″ tiles aren’t going to conform to anything. You may be able to do it if you have a grout line at the lowest spot and it does in fact slope up consistently, but you’ll also have the problems at the top of the slope and that slope WILL be noticeable with tile that size. You can’t see it now – but you will see it once it’s tiled.
Dearest Roger,
I think you can help me with my problem (problems? 5 bathrooms dagnabit). My father recently died, very suddenly, and left behind a 1912 house in the midst of renovations. After much “debate” my family has decided to keep the house, now that we have realized it REALLY is a diamond in the rough. Lots of rough though I gotta’ say…
All the very sad 1950’s linoleum bathroom flooring likely involves questionable adhesive materials and my head is reeling from all the information I have tried to absorb online. I have come to the conclusion that it is best to leave the questionable flooring intact and tile over the top of the sheet flooring. I think using backerboard and tile is a good solution for us.
PROBLEM (well, one of the MANY problems): One bathroom has questionable sheet flooring that appears to be partially ripped up for plumbing issues, to the wood sub-flooring, which sadly, is quite beautiful *sigh*. Someone(dad?) taped it over with plastic to contain any asbestos contamination issue. What is the best way to level out a floor that is partially torn up, down to the sub-flooring without removing any additional flooring? Is this where floor leveling compounds come in? Do I need to coat the wounded area over with anything to seal it up? Will the leveling compound take care of that?
I appreciate any advice that you can give me to fix that :censored:floor.
And I just wanted to use this emoticon. Just ’cause.
Thanks and have a beautiful day!
Hi Brenda,
Self-leveling cement is likely your best option there. No need to patch anything into the missing area if you don’t want to, the slc will fill it. You can, of course, it will use less slc that way.
Hi
I would like to tile a floor that currently has carpet and tiles. Is there anyway I can rip up the carpet and tile the whole floor (over existing tiles) while eliminating the height difference between the two areas. If I have to chisel up the tiles I will however they go under all the kitchen benches.
Never tiled before,,, Shell
Hi Michelle,
You can, although I don’t like the whole tile over tile thing. You need to use a thinset approved for that application and add some sort of substrate like backerboard in the area which are currently carpeted. You need to bring that floor level up to the level of the top of the tile before setting any new tile. You’ll also need a soft joint above the seam from one substrate to the other.
Did you know that you can remove the tile from under the cabinets if the tile is less than 20% covered by the cabinet without damaging the cabints? Just lift up on the opposite end. You can also bust out most of the exposed tile and use a hammer and screwdriver or some other form of dull chisel to remove the remaining pieces. That would be my recommendation. But I’m not the one removing your tile, eh?
Hi Roger,
Got a bit of a bind. working on a large area approximately 400 sqft.
what can I do now?
I install 1/4 wonderboard on top of my osb board with custom mortar and lots of screws, hot glued floor heating mats everywhere but where my cupboards and island are going to go and then poured self-leveling compound on top and tried to level the best I could. I can still see the mat and heat wire in some areas.
Dry ran my 24×24 porcelian tiles and i have some tiles that are a little higher then the rest but flat and a few that not flat. I have already spent so much on the leveling compound.
Hi Julie,
Unless it’s more than 1/8″ or so difference on the higher tiles you can make up that difference with more thinset beneath the lower tiles as you install them. You can also install a bare layer of thinset over the entire area to even it out some more, let it cure, then install your tile.
Hi Roger,
Thanks for the quick reply.
If I decide to install a bare layer of thinset over the entire area to even it out some more. What do I need to do for prep? Do I need to prime?
How do I know if I am level in the end and if I am adding enough or too much to the areas that require it?
I’m thinking I can rigg up plates with a string or something like that
Do you have any suggestions?
There is no way to tell, or even get it absolutely flat with thinset. The only thing you’re doing is evening out some of the bumpier spots. You’ll get it all flat as you tile it. If you want it absolutely flat first you need more slc. No need to prime first for the thinset.
Hi Roger,
Ok, thanks for the advise. I will do my best to level out the high spots and see how it goes. My biggest fear is having my tiles crack in the future. Doing it right to prevent that is what I am trying to accomplish.
Sincerely,
Julie.
As long as you have full coverage beneath your tiles you won’t have any cracking.
Hi Roger,
My husband and I just bought a house (built in the 1960s) and are gutting the kitchen and bathroom. We are planning on putting porcelain tile in both rooms. We tore out the flooring all the way down to the 1×6’s laid diagonally across the joists (2x10s I believe). We went around and screwed down the 1x6s to take care of any squeaks and then laid down backerboard. We did not (please don’t yell) put thinset under the backerboard. We just screwed it into the 1×6’s and used longer screws to hit the joists where we could. The floor seems pretty secure, however there are high points and dips. We took a level to it last night and realized the uneven-ness. We are hesitant to use leveling compound because the flooring abuts to existing wood floor that also slopes (I’m assuming from settling) and we don’t want the kitchen floor to be higher than parts of the wood at the threshold. Some of the dips may be close to 1/2″ between a high and low point. Can we get away with using mortar to even out the floor as we lay the tiles?
I should note that the existing 3/4″ wood floor is laid directly on the 1x6s in the adjacent rooms. We are really hoping to get the kitchen tile flush with the wood floors so with the 1/4″ backerboard, we only have 1/2″ to play with for mortar & tile.
Same answer.
Hi Katie,
Only if you use a medium bed mortar. Most thinset can not be built up more than 3/8″ or so without compromising the stability. My advice would be to remove the backerboards and install thinset beneath them, get it flat and let it cure, then screw it down.
Hi Rodger,
I am a first time remodeler and I have run into a problem. I decided to put new tile in my bathroom. I started with a flat wood surface, but I don’t have one now.
OK, I put down 1/4″ plywood over my subfloor. Then I put down thin set and then backerboard. Now I have dips on the surface on the surface of the backerboard, probably less than 1/4″. My 13″ square tiles do not lay flat when I put them down for a dry run. Do you think a medium bed mortar will solve the problem or would you use something else before laying the tiles?
Kim
Hey Kim,
A medium-bed mortar and a 3/8″ trowel should solve your problem just fine. Just take your time as you set them and it should come out nice and flat.
Rodger,
Thanks for getting back with me so quickly. I am on my way to
the supply store. I have to get my tiles cut outside before it
snows!!
K.
Hi Rodger,
u instructed. Now, I have a tile lippage problem. Is there anything that can be done at this point? 
From bad to worse, Ok, I put the tiles down very carefully as yo
Kim
Not once the tile is set and the thinset cured. You can remove the tile and reset it, but you’ll likely destroy the tile in the process.
Roger
I used self levelling cement to make my floor flat. I think I mixed it too thick and now the cement is uneven. If I mix a runnier self leveling cement can I even it out easily enough or do I Ned to rip up the whole darn thing and start again?
HELP!
Steve
Hey Steve,
You can install another layer over it as long as you use the primer over the top of the first layer. If you do that it’ll bond just fine.
Hello, are subfloor dips down on the right side just in front of the mirrored, sliding closet door that runs the entire length of that wall. This is making our tile rock. We can’t raise it being right in front of the track or it will be obvious when the tile sits above the track. It is not an option to remove the track, as it is glued straight to the floor, there are no screws. Is there a way we can remedy this so that we can put down the tile, have it be level and not be raised above the track?
Hi Penny,
There’s no way to install it flat and do what you want. You can have a grout line right at the top of the dip, where it begins to flatten out, but you won’t be able to install it flat without changing that track.
Roger,
Great site you have here. So glad I stumbled across it. I am starting a remake of a small bathroom and after removing peel and stick floor tiles and a 1/4″ plywood sustrate I am left with 1/2″ plywood sub floor on wood joists 16″ oc with a 3/4 plywood on top of that. I am planning on doing a 12 x 12 porcelain tile on Ditra and I want the transition to the hall floor to be as close as possible. The current 1/2 + 3/4 combo is about 1/8″ below my finished hall floor so I really don’t want to build up on that. The 3/4″ ply also has some old adhesive from previous peel and sticks with rosin paper stuck to a lot of that.
My thought is to take it down to the 1/2″ sub floor and insure that is properly nailed/screwed and then put 1/2″ plywood on that. Attach it properly and then go ahead with the Ditra.
What are your thoughts on this approach. Also, we have 5 dogs so if I cause one to catch fire do they all catch fire? That could be ugly.
Hey Mike,
I don’t see any reason why replacing that 3/4″ with 1/2″ would be a problem. The 3/4″, of course, is a bit more stout, but being that you have stuff on the 3/4″ it’ll probably end up being better anyway.
Don’t think they all burst into flames simultaneously, perhaps at regular intervals?
Roger. Thanks for the helpful advice. I have a couple of more questions if I may. I have a 1/4″ dip in the middle of my floor and I wanted to know if I should flatten it by using thinset between my subfloor and the additional layer of plywood that needs to go down or should I get it flat when laying my Ditra to teh plywood? Secondly, I glean (nice work right?) that you are a screw guy
but I would like your take on the diffrence between ring shanked nails and underlayment screws. And lastly (for now), I am installing a tub with a radiused skirt and I was thinking of laying teh tile under the skirt instead of trying to cut a clean and uniform gap in tiles layed up to the skirt. Is this a case of spontaneous canine immolation waiting to happen or not? Thanks again.
Hey Mike,
It’s easier, quicker and more stable if you make up the difference between the ply and ditra. I do prefer screws, but galvanized roofing nails are approved for it. Ring shanks are not, I have no idea why unless it’s the propensity of the metal to degrade over time. Alkali in thinset eats a lot of stuff.
I normally install all vertical tile over the horizontal when I can. Dog hasn’t combusted yet (because of that, anyway…)
Thank you again Roger. I’ll go with the screws so I don’t shake things up with countless hammer blows on the second floor. Should I just use thin set to make up the 1/4″ or use some slc first?
The tub skirt is not being tiled. It is a Kohler acrylic tub that is radiused. That is why I thought it would look cleaner to run my floor under it. I am certain that I don’t have the skill set to make smooth enough cuts to match my “attention to detail” personality. I fear it would take countless tiles and many amber beverages to satisfy myself. Then again, if I take advantage of enough of said beverages prior to doing those cuts, I might not notice the inconsistencies.
The thinset should work fine Mike.
With those types of tubs it does look better with the tile under it. Enjoy the beer anyway.
Hey Roger! I am beginning my first bathroom remodel and although my hubby has done this kind of work before, from your site and I am learning that he hasn’t done things exactly right. But, since I am the “foreman” he says I can do things “my way” or as he likes to say the “long way” if I want. Ha Ha. So last night we pulled up the vinyl flooring in the bathroom which was glued to 1960s linoluem flooring that was glued to the subfloor. And I mean glued— this stuff was meant to outlive the apocolypse. As we are pulling it up, it basically peeled leaving the backing on parts of the floor. My husband says that we need to scrape all this off before tiling. I thought we could put down our thinset and backerboard on top of this and not spend hours trying to peel this crap off the floor. It does not seem to want to budge. What do you think? We haven’t taken the tub out yet, but I think this plywood flooring may be actually be placed over the subfloor as this layer goes to the tub and the tub appears to be directly over the subfloor. If this is the case, should I remove this subfloor, replace it and then put down my backerboard? Of course, hubby doesn’t think we need backerboard, but the foreman thinks different thanks to you:)
Hi Beth!
I feel your pain, just ripped out some of that today myself. I have power tools for that, though.
You are correct, twice. You do need backerboard (or a proper tile substrate) and you can place thinset down and backer over the top of what you have. I think you can probably leave that subfloor down without a problem provided it’s in good shape and solid.
See, this time your way is the short way.
Excellent to hear this. I’ve been trying to figure out what to do with the floor in my kitchen. We pulled up the laminate, and under that was 1950’s era vinyl (glued for the apocalypse, and stapled for good measure, just you know, in case). With two people we spent a full day removing the vinyl (150 sq ft kitchen). Now we have a thin layer of black ugly looking glue remains on the floor that I was really hoping I could thinset/backerboard over. And sounds like you just confirmed it.
The floor itself seems fine, half foot wide planks diagonally on top of the joists with plywood on top of that. With the thinset & 1/4 inch backerboard it should be a decent surface (at that point, backerboard will be level with the dining room laminate, so tile on top of that will be high enough. Can’t really justify going higher than that. Don’t want stairs into the kitchen)
Small question. With dining room being laminate and a touch lower, and kitchen becoming tile. Would a tile ledge or laminate ledge be better suited to cover the edge between the two? Or is it personal preference (ie whatever the wife thinks will look good)?
Hi Jeroen,
Whatever your wife thinks looks good.
I prefer the metal tile transitions because they both protect the tile and allow you to change the laminate flooring without problems should you choose to do that down the road.
Turns out the whole issue was moot anyways. What I referred to as plywood was really (after pointing at it at the Home Depot) particle board. The stuff cupboards are made out of.. Not flooring. (Due to water damage it had expanded in various places, making for a non-flat surface)
So out that came tonight.
My floor is now joists (16″ OC) with what seems to be wooden planks diagonally on top (they cover the whole first floor, not just the kitchen. And they creak a lot). I am really hoping those are fine, and I can just get away with putting the plywood on top, then the backer board and finally the tile. If I’m making a mistake, holler now.
Nope, you should be just fine with that. You should also screw those planks to the joists so they don’t squeak, but you already knew that.
Right, of course I did.
And lo and behold, with 5lbs of 1 5/8th screws (about 700 screws for 150 square feet), the floor no longer squeeks. Plywood is on, and I’ve got 2/3 of the backerboard set (after which my thinset got too thick to continue. Putting that down, and then screwing in the backer board takes a lot of time).
Next time I think I may measure out half a bag of thinset. That should be enough for the floor, and then make up the other half for the seams & tape and first couple of tiles.
Hi,
I have tile that is cracked in a line that goes from one side of the room to the other. Do you think that they did not leave room for expansion? Or do you think that my slab is shifting or cracked? Thank you for your help!
Hi Mary,
If it is directly on concrete it is likely that the area is directly over an expansion joint, which will move, and there was not a soft joint installed over it.
I have an area of my floor that goes from over the basement to a crawl space. At the junction, the floor slopes slightly enough that when I lay tile, I end up with “lippage.” Is there anything I can do to prepare the floor at this junction for tile so I don’t end up with “lippage.” Beyond and before the junction, the floor is fairly flat.
Hey Steve,
It depends on how much of a difference there is between the two planes. It could be as simple as using more thinset on each side of the threshold and as difficult as completely building up one side or the other throughout the room. How much difference is there?
Hello Roger,
Thanks for all the great tips. I am about to start my first bathroom remodel and this will be my first time tiling. In Oklahoma our foundations are concrete slabs set in red clay. The foundation tends to crack as the house moves and settles. I noticed a few hairline cracks when I installed my laminate flooring in the living room. Should I be concerned if I find more cracks once I pull up the linoleum in the bathroom? Is there anything special I should do to ensure my tile won’t crack along the foundation cracks? If I need to install piers to fix the foundation, will this affect the tile in the future? The bathroom is small, about 45 sq ft.
Thanks,
Matt.
Hi Matt,
If you find more cracks you’ll need to install some sort of crack suppression membrane over the floor before tile. There are several available, redgard is actually a crack-suppression membrane as well as a waterproofing. Ditra also works as one. If you add piers in the future it depends on the structural load points in your particular floor in relation to where the tile is installed. It may or may not – I can’t see it from here.
Hi Roger,
We are remodeling our master bath. We bought marble tiles. Can we put the marble tiles over the existing ceramic floor?
Hi Gabrielle,
You can, but you first need to ensure that your floor is strong enough for not only the stone, but to support both installations without excess deflection. You also need to scarify the surface of the existing tile and use a setting material approved for tile over tile installations. With marble I would highly suggest not doing that. I would remove what is currently there and start from scratch building a proper substrate.
Many thanks!!! Exactly what I was hoping you’d say. Especially since I already have the adult beverage in hand.
I hired a home improvement company to put tile down in my bathrooms. When they pulled up the existing linoleum there was mold around the toilet. I asked if they were going to replace the plywood and he said, “no we will spray it with bleach. They put down the mud, hardibacker, more mud then tile. For some reason this just hasn’t set well with me. Am I being overly concerned?
AAAAAARRRRRGGGGGGGGGHHHHHHHHHHHHH!!!!!!!!
BLEACH DOES NOT KILL MOLD!!!
*ahem*
I’m better now.
That being yelled – as long as the substrate was still stable and they allowed the substrate to completely dry out (which actually will kill the mold) then you’ll be fine. Mold requires moisture to propagate – take away the moisture and it dies. Spray it with bleach and it will turn white, then laugh at you while it continues to grow. Wherever there is mold needs to be thoroughly dried out before moisture is introduced to it again – then you won’t have a problem.
Thank you for responding so quickly! Sorry for causing frustration. There’s no way the subfloor was completely dry. They sprayed it and had the tile down within three hours. Sure wish I’d followed my instincts. They were highly recommended so I thought I could trust them. The floor looks great! I asked them twice if they were certain it would be okay. Yeah, yeah no problems. They are friends of my parents and gave me a great deal. This is their specialty and have been in business since 1996. I’m really bummed now and not sure what to do. Maybe I should call them and ask if they let it dry. What can I expect will happen if the floor is left like it is? Is it possible that it dried with the mud on top of it? Thanks so much for your help.
If they had a cleavage membrane (tar paper) beneath the mud then yes, eventually it will dry over time provided no moisture is introduced beneath the tile. It should eventually dry out. The issue would be how much mold is going to grow before it does? How much mold was there?
No tar paper. The mold was around the toilet. A foot on either side and behind the toilet. The substrate was discolored but wasn’t warped; I don’t think it was still wet. The problem that caused the moisture has been fixed.
It’ll be just fine. Go have an adult beverage.
Roger,
Great site! Hopefully you can help me out. Installing electric radiant heat mat in my main bathroom under 12X12 Ceramic tile. The house has a concrete slab, which was in great shape after I removed the mud bed that was destroyed when I took the old, 1960 tile out. I installed 1/4″ NAC backerboard over the slab as a thermal break using thinset. It came out really flat, but that is when I realized the floor was out of level one inch over 10 feet (the total length of the bathroom). There is a marble threshold (already installed) that is just the right height for the tile/thinset/heating mat. The floor tapers down an inch at the outside wall. What should I do to try to raise it up? SLC, your favorite Mud Bed, or leave it (hack)?
Hey Jeff,
SLC would probably be your best bet. It can taper down to nothing whereas your mud bed will need to be a minimum of 3/4″ all the way through, which means it’ll raise your floor at the threshold 3/4″. That’s the way I would address it if your doorway is currently at the correct height.