There are three basic materials used to set tile.
- Mastic
- Thinset Mortar
- Epoxy
For each installation there is a specific material you should be using. Before you start any tile installation you should ensure that the material you choose is suitable for that application.
Mastic
Mastic is a latex or solvent based adhesive that cures by evaporation. It is sold in airtight containers (buckets) and requires no mixing. It is ready to use immediately. It is suitable only for non-wet applications.
Mastic should never be used for showers or floors! Ever! When mastic gets wet the water will re-emulsify the adhesive base. This means that mastic turns to goo when it gets wet. Goo will not keep your tiles on the wall. Every one of the failed showers that I’ve ever replaced were installed with mastic.
With that said typed, mastic does have its place. It is “stickier” than thinset mortar which is why some prefer to use it – for everything. It should only be used in non-wet areas such as a backsplash, wainscot, or fireplace. An area that is not consistently exposed to water or moisture. It should also only be used on tiles smaller than 6 inches square.
Think about it like this: mastic is stored in a bucket with a lid on it. This keeps it from being exposed to air which would cause it to cure (dry). If you spread it on your wall and place a 12 X 12 inch tile on it, that’s just like putting the lid back on the bucket. It will never fully cure. If any moisture gets behind that tile with the mastic it will eventually re-emulsify and lose adhesion. That means is that your tile is going to fall off the wall.
There is also a product called “premixed thinset adhesive”. This product is pushed as a suitable material with which to set tile – it is not. It is only mastic with sand added to it. While sand does help materials from shrinking as it sets, it does not make mastic suitable for showers or floors.
Thinset Mortar
Thinset mortar is what you need to use for shower walls and floors of any type. It is sold in bags and needs to be mixed with water. Sound simple? It is. Referred to as thinset, mud, mortar, or a number of other things, it is a combination of sand, portland cement, lime, and other stuff that makes it the preferred setting material for elves everywhere.
When mixed properly (read the directions, no, really, read the directions) it is stable, not compromised by water or moisture, and rock solid. Thinset must be mixed with water, allowed to slake, then remixed before use. Slaking refers to letting it set for a specific amount of time to allow the chemicals to interact and become workable.
Thinset cures through a chemical process, not by evaporation. Air is not required for it to set. It will cure in the bottom of a bucket of water, really. This means that no matter the density or type of tile you use it for, it will fully cure. No worries there. The tile will stay where you put it.
Unlike mastic, thinset will not be compromised by water or moisture. If it gets wets the thinset will remain cured and will not be reactivated. It’s similar to your driveway. The concrete on your driveway was mixed with water but it doesn’t turn to mush when it rains. It’s the same stuff.
Thinset mortar will be the correct setting material for nearly every application.
Epoxy
Epoxy is a chemical based glue that cures through chemical interaction. It is almost bulletproof and not user-friendly. To be frank, it’s a pain in the ass. It is usually a two or three part product which, when mixed together, form a very stiff, very thick putty-like substance. When cured it becomes a permanant part of whatever is attached to it. That’s great on the back of the tile, not so much if you get it on the front. Use with care, it is nearly impossible to get off of anything once it’s set.
There are not many applications which require the use of epoxy setting materials. Certain exterior applications need it, swimming pools, certain types of stone and glass tiles. While epoxy can be used for any application, only specific jobs actually require it. It’s expensive. I mean really expensive. If you don’t need to use it, don’t.
If you are unsure whether or not your product or application requires epoxy, just check the manufacturer’s recommendations. If it is required, they will make sure you know about it. You can also ask me, just leave a question in the comments. I’ll reply, I’m a fairly sociable guy when I’m not crawling around on a floor.
Which to use
The general rule of thumb is to use thinset mortar. Unless your specific application requires epoxy, thinset can be used. Anywhere you can use mastic you can use thinset instead. It is more durable, water resistant, and cheaper than mastic anyway. As far as I’m concerned, the only thing mastic is good for is a free bucket.
SIR ROGER,
IS THERE A BRAND OF MODIFIED GROUT THAT YOU RECOMMEND I USE ON FLOOR TILES THAT IS AVAILABLE AT MY LOCAL LOWE’S STORE, I SIMPLY WANT THE BEST THAT IS AVAILABLE,
NOT REALLY CONCERNED WITH PRICE, COMPLETELY CONCERNED WITH QUALITY!!!
ALSO,ANYTHING ELSE YOU HAVE TO SAY IS MOST WELCOME!!
THANKS, DANNY…..
Hello Sir Danny!
I believe Lowe’s only carries Mapei grout, mine does anyway. If that is available it is a good grout. With mapei, though, you want to make absolutely certain you follow the directions on the bag when mixing with the exact amount of water, slake time, etc. This will eliminate any problems with discoloration or unstable grout.
Anything else I have to say? Well, the next time my yak has a flat tire I’m callin’ the spider monkeys!
Thanks for your comments – you rock! 
Hi!
Thanks for all your previous help in figuring out our waterproofing method. WE’ve got our tiles up on the walls in our shower (and I must say…looks fantastic!). What we’ve found is that even after wiping down each tile, there’s a bit of a haze to the tiles from the mortar that came in contact when putting the tiles up…off of dirty fingers, etc. Is there anything I need to be doing other than just continuing to wipe them down to try to get rid of the haze?
Hey Kathryn,
Nope, just keep wiping – it’s a pain in the ass.
You can try a 50-50 mix of white vinegar and hot water. It’ll smell like crap but it usually gets rid of the haze. It will also help if you wipe it down with a microfiber towel.
MORNING ROGER…….
Am doing a tub to shower replacement and thinking about using a preformed pan made by ” Tile Redi” .. they sell an epoxy and suggest using it to set the tile to the base… want to use a small multi sized floor tile, on a sheet, which sets the grout space.. was wondering if you have any info using the epoxy and small tiles .. will the space between the tiles get filled with the epoxy and cause problems in grouting ..
also what lb set of epoxy would you recommend ?? they sell a 6# / 9# / and 12 # ??
thank you, -shayle
Hey Shayle,
The epoxy will work just fine for setting those mosaics. I would use a 3/16″ v-notch trowel and knock down the ridges (that just means after combing the epoxy on, flip your trowel over to the flat side and lightly go over the top to knock down the ‘V’s’), that will minimize any squeezing through your grout lines. I’m thinking the 9# but I’m really not sure, I don’t use tile redi pans. I’m sure they have the recommended size for your specific pan. It would be better to have too much, if you run out it creates a big ole’ mess.
I am working on remodeling my 1940’s bathroom. Instead of removing the concrete walls and that old metal mesh material, we removed just the old tiles and leveled and smoothed the walls with joint compound.
My question is, should i paint the joint compound with redgard before I put the tile up with thinset? I read that thinset and joint compound doesn’t go together, especially in wet areas. Thank you!
Hey Jeremy,
You’ll need to do something with it because that joint compound will disintegrate when it gets wet. Ideally you should remove all the joint compound and use regular thinset to smooth out the walls – then you’ll be fine. You can use redgard if you wish but in that case you should use it in the entire shower – that gets expensive. Soak that joint compound down really well for a while – it’ll come out easily.
Damn. Well the joint compound covers 100% of the shower walls. Taking it down would be a nightmare because it isn’t just a light coating, it’s thick in some parts and its keeping my walls level. Since I can’t travel back in time and do it right, I think coating it entirely with Redgard would be much more ideal. I know that stuff is costly, but I feel like I have no choice at this point. So do you think a layer of Redgard, on top of 1/2″ thick joint compound on top of old concrete walls is acceptable?
Thanks!
Well shit, Jeremy – that’s no good.
Covering it with redgard at this point would likely work all right. A better option would be to use kerdi on all the walls. Being a sheet membrane you won’t run the risk of the joint compound sucking in moisture as it may with the redgard. I don’t know that it would do that for sure but it may create weak spots in the waterproofing if you use redgard. The sheet membrane won’t have that problem.
Thanks Roger.
Hi Roger,
Do you have any comments about these new products for setting tile: Bondera (Lowes) and Simple Mat (Home Depot)?
Thanks for all your help!
Sharon
Hi Sharon,
You’re asking me if I have comments about a tile setting product???
Just kidding.
I haven’t used either of them (and am likely never to use them) so I really can’t speak to the effectiveness nor durability of them. From what I see and what I’ve heard they may be a viable product for a (very) small backsplash in a kitchen or bathroom although I don’t know that I would trust them long term. They may last – I just don’t know. I do know that your substrate must be absolutely clean and dust-free before installing them, that may or may not be a problem. I don’t believe the are supposed to be installed over paint although I’m not certain about that either. I would never use them in a shower or anything like that
Personally I probably wouldn’t use it, but I have a LOT of experience using simply thinset to set tiles – and I know that will last.
Sorry I’m not a lot of help this time.
using one inch mesh backed tile in shower. thinset ultra 2 tile placed in shower cured one week. When testing shower and drain before grouting water loosened and freeded many tiles we tested each tile all were bonded securly before they got wet. does the grout water proof and lack of grout cause this proble lowes told us this was cause. thanks
Hey John,
Whomever you spoke with at Lowes doesn’t know what they’re talking about.
The problem is due to a combination of two factors – the glue on the mesh and the coverage on the tiles.
When setting mesh-backed tile it is imperative that you get a LOT of thinset in the bed to set the tile into. This is so that the thinset will fully contact the tile where the mesh is not.
The second factor is that most glue that holds the tile to the mesh is water-soluble. When it gets wet it dissolves. So when you tested the shower and got the mesh backing wet the glue dissolved, since the tiles were not 100% bonded in some areas the glue was the only thing holding it together.
Grout will not waterproof this or solve the problem – the loose tiles need to be taken off and reset with mortar. The tile will remain the same whether it is grouted or not. They need to be adhered properly to the substrate.
Hey Roger,
I work for Lowe’s and I am totally new to flooring, you are so right about the workers not being trained have been there for 5 months and I have to do research on my own time to learn about all the products we sell, it would be smart to train the employees with classes but that’s never going to happen, so all the info you have been posting is really helping stay above the pack at work, I will be applying for flooring specialist in a couple of months because unlike most of the employees in home depot and lowe’s, I am actually looking to make a career in home improvement, keep posting because I need all the great info I can get. Key
Hey Key,
That is great to hear! I’m glad there are a couple of you guys that actually care whether or not things are done correctly and aren’t just in it to sell as many products as possible. Keep up the great work!
Hi Roger,
I have a question on a kitchen backsplash. My current house I used Mastic on sheetrock with 6″ square tiles, 7 years ago and have had no problems. I am now remodeling the kitchen in a house I purchased and will be using larger format tile probably 12″ square. Wanted to update the electrical to 2 wire with a ground. Helps to keep from getting your batteries recharged by accident. So the existing sheetrock was removed wiring done then replace with green (mold resistant sheetrock). I have read in some of your post that you should not tile on the green sheetrock in a bathroom will it be a problem to use modified thinset on it in a kitchen?
Hey Dennis,
Nope, won’t be a problem at all. The problem with green board is when it get continuously wet – it falls apart and feeds mold – not so good for a shower. It’ll be fine on your backsplash with modified thinset. Cement backerboard would be better, but you knew I was gonna say that.
Roger,
You are right I knew you were going to say that backer board was best. I wish they made it in 4’x8′ or 4’x4′ sheets though. I know the reason for 3’x5′ sheets is because it is the right size for the back wall of a 5′ tub enclosure. The 3’x5′ size makes it a P.I.T.A. for other wall applications because ti does not fit 16″ center studs. Lots of cutting and wasted material but that way they get to sell you more sheets.
Dennis
Hi Roger,
We’re in the midst of some major renovations around here & considering tiling the kitchen counter tops. The other option is a lovely Bianca Carrera Marble we’ve found & really really like – but since we could tile the space for, oh, 1/10 of the cost, we’re doing a little more research on the subject.
I’d use Ditra over a nice solid wood substrate (I’ve done ~500 sq ft of floor with Ditra so far), but my concern comes when I get to the grout. I would use a pretty large tile with as small of grout lines as possible. Is there any way to keep the grout from looking like stained crap in short order? I cook – a lot – with a lot of tomatoes. This grout question is the only thing really holding back the decision to tile the kitchen counter.
Any recommendations? Do you think I’m nuts to be considering tiling (grouting) such a high use area?
Hi Sharon,
Yup, granite tiles are considerably cheaper.
There are two ways to guarantee that your grout will never stain. Since one of them involves never using your kitchen, I’ll talk about the other one.
The other way, in case you actually want to use your kitchen, is to use SpectraLock epoxy grout. It is stain-proof. In case you’re curious or skeptical about the ability of it to withstand stains you can read about my little experiment in which I reveal the most toxic substance on the face of the planet – and dunk epoxy grout in it – for weeks. It’s here: Stain Resistance of SpectraLock.
It works – really. I have it in my own kitchen. Hope that helps. Until then – Fahrvergnügen!
Cool. I’ll have to see if I can get that here! (I’m in Canada) A little more research is in order….
I’m actually looking at ceramic tile rather than granite.
Thanks.
Hi Roger,
I wish we’d found this website before getting started on our tiling project (I bet you hear that lots!). Here is our not so brilliant report: We are tiling a shower in the basement with small travertine tiles that are mounted on mesh (13″x13″ sheets, about 20 tiles per sheet ranging from 2″x2″ to 2″x8″ in a random pattern). On the advice of Home Depot, we started using Acryl Pro Ceramic tile adhesive to put up the tiles (and the iinstructions on this product says showers are okay!). Then we found your site (I was looking up how to grout in corners) and I saw the post on NOT using mastic in showers. So, I took a sheet of tiles off the wall to see what is happening, and five days later it’s still as gooey and wet as the day we put it up. I was able to scrap the mastic off the wall easily, but of course it is not so easy to get it off all those small tiles. In fact, the mesh backing has fallen completey off (I think the glue holding the tile to the mesh released due to the moisture of the mastic). We are now realizing we will have to take all the tiles off the wall (about 15 sheets already put up, plus some accent tiles. Yah!). I guess my question is: can we reuse those small tiles? I realize it will be a lot of work relaying the pattern on the wall instead of putting up sheets. I’m willing to do it if the tiles will stick – but I’m wondering if they will without the mesh backer? There is no texture or anything on the back of the tiles to help them grab the mortar, now that they are cleaned of glue and mastic. The back is just like the front. So will they stay up with mortar? Please advise. Thank you!!
Hi Corinne,
Yup, Home depot strikes again. Sorry about that. (and yes, I do hear that a lot!) The good news is that yes, you can reuse those tiles. Travertine is a very porous stone and has plenty of microscopic ‘pits’ for the portland crystals in the thinset to grab onto. It’ll stick just fine – with thinset.
If your travertine is light or lighter you should also use white thinset – the gray tends to darken the look of the stone.
This time I have some authentic brilliant news to report – I decided to call HD, explained what happened and they have actually agreed to replace the tiles that we have to pull down!
I’m so happy I don’t have to clean all those tiles and put them up individually.
Thanks for the info and the tips on the white thinset. The tiles are cream/beige/brown so that would probably work better. Your website if bookmarked for reference before we tackle any further tiling projects
Hey Corinne,
Well, that is good news! Most of them don’t do that. You would think they would figure out that it’s cheaper to train someone than to replace things, no? Oh well, glad they’re doing that for you.
Have fun!
Roger
Got a quick questions for you. Can ultraflex 2 tile mortar with polymer be used in the shower?
Hi Michelle,
Absolutely you can – it’s good stuff.
Hello, love the site…it rocks!!!
I will be installing a new acrylic tub then tiling the walls around it with 12″ porcelain tiles. Starting at the studs I will be installing 4 mil sheeting, then using 1/2″ Hardiebacker (keeping 1/8″ gaps between each sheet which will be taped and thinsetted and resting 1/8″ above the tub flange) Does the Hardiebakcer still need to be waterproofed before tiling or can I start tiling, I will be using thinset for tiles?
Also, where the Hardie backer will vertically meet the 1/2″ drywall on the rest of teh bathroom wall I will be placing 12×3 bullnose tiles (just outside of the tub) I am planning on taping and thinsetting the gap there as well, is this correct?
Thanks-Jeff
Hey Jeff,
If you use the 4 mil sheeting behind your hardi you do not need waterproofing on the face of it – just thinset and tile. If you are using a topical waterproofing (Kerdi, Redgard, etc.) you use only that without the sheeting behind the hardi – One or the other, never both.
That is correct – tape and thinset that joint between the hardi and drywall. You can simply paint any area that is not covered with tile. You can also use regular wall mud there rather than thinset but if you do you need to use the powdered stuff – not the stuff in the bucket, it won’t hold up to moisture. The powdered stuff will.
Thanks for the kind words! You Rock!
Roger,
Will thinset adhere to ICF (Insulated Concrete Form) block? After using your great advice for our shower installation, I thought you might have some insight about ICF. We are doing a backsplash in our kitchen and would like to tile directly to the ICF (IZO BLOC), but have not found info from manufacturer regarding this. We have used Perma Crete for our exterior and interior walls, which is a cementious product, that adheres perfectly well after a modest rasping of the bloc. Thanks!
Russ
Hi Russ,
That’s a damn good question!
I’ve never tried. The thing that would determine that would be the density of the foam. Most of these blocks (from my understanding) are made from Expanded Polystyrene (EPS) which tells me that it may or may not. That’s a lot of help, huh? About the only way to find out is to try it. Mix up a bit of thinset – I would use a good modified – and stick a piece of tile to is. Right next to that spread some of the thinset on the block with the flat side of your trowel. This will let you see how it cures – consistently, slowly, etc. to give you a better idea of what is happening behind that tile. In a couple of days try to rip that tile off of it.
Oh, do this in an unused, unseen area or with an extra piece of said block. If the tile sticks well it should tear the foam apart when removed. If you destroy the foam, well, it sticks.
I would like to know if it would be possible to tile a bathtub, if so should I use epoxy thinset? Is this do-able
Hi Janis,
The short answer is no, you cannot. The problem is not getting the tile to stick to the acrylic or fiberglass – epoxy will do that – the problem is that the epoxy will not allow for the movement that will take place. Different materials expand and contract at different rates. That means that with seasonal changes the acrylic or fiberglass (or cast iron, if that is what your tub is made of) will expand at a different rate than the tile you adhere to it (and the setting material you use). A tub will also move excessively every time you fill it with water.
All this movement creates stress on the bond of the tile to the tub. By constantly straining this bond in different directions and at different rates your tile will eventually simply begin falling off. Even epoxy cannot take the stresses inherent with a bathtub.
Thanks for the info, very useful. I’ve been thinking about this for a while and couldn’t get any answers
Hello Roger,
I am learning quite a bit from your site and really appreciate that you take the time to educate all of us who like to do it ourselves. I wrote previously about our upcoming master bath project using onyx. Will the thinset work with the onyx or do we have to use epoxy adhesive? I take it from all the reading I’ve done, we should use the spectralock epoxy grout. Is that the right choice? I’m sure I’ll have more questions over the next couple weeks and I thank you for your time and expertise!
Hi Elizabeth, welcome back! Glad I haven’t scared you off!
Unless your onyx is from a very unique manufacturer, and you would know if it was, you should be fine using a higher-end (read expensive) modified WHITE thinset. Be absolutely certain you use the white. The color of the thinset will show through due to the translucence of the onyx. If you use gray it will show through and significantly dull the color of your onyx.
Just to be certain, though, you should be able to contact the manufacturer to see if epoxy is required. If it is they will let you know. Every manufacturer will tell you anything you need to know about their product – they want it to be installed correctly and want it to last. They will tell you how to make that happen.
Spectralock is absolutely the way to go. As I’ve previously stated it is the ONLY epoxy grout I will use – period.
Thank you for the kind words and the time I spend is absolutely my pleasure if it helps people avoid incorrect installation and, in turn, developing a negative opinion of tile in general and contractors such as myself in particular. I’m only out to save the world. I’m just super cool like that.
I’ll always be here for any further questions you may have.
I’ve got some pictures to send you. What’s the best way to do that?
Hey Elizabeth,
Pictures – Yay!
The absolute best way to do that would be to build me a robot and send him to me (with your pictures, of course) on the back of a saddled yak escorted by a herd of turtles and a platypus. After he delivers your photos I could reprogram him to shoot lasers and make me toast. Together we could take over the world and finally dominate the chocolate-covered baked goods market.
Crap, did I just type that out loud?
Or, you can just send them to Roger@FloorElf.com.
Now, needless to say I do prefer the first one, ’cause I’ve always wanted my own slave robot. But, you know, whichever is easier for you would be fantastic.
We just tiled our kitchen counter tops. We used a non-sanded grout (1/16 grout lines). We used a silicon sealer on the grout lines according to the manufacturer’s instructions. Recently, I’ve noticed that the grout is shrinking and pulling away from the tile… what gives?
Hey Nick,
The problem has nothing to do with your sealer – it’s a grout issue. To be able to help I would need to know the type of grout (brand) you used as well as the color. If it is a darker color it tends to set up more quickly which means it probably never got a good grab on the tile in the first place.
If it started to set up prematurely it never would have grabbed the tile and probably had micro-cracks along the edge of the tile which you would not have been able to see. The grout continues to shrink as it sets and is not fully cured for about 28 days.
Unfortunately there really isn’t much you can do except this (and yes, I know you don’t wanna hear it – sorry) The best thing to do at this point would probably be to dig it out and regrout it. Make sure you follow the directions on the grout to the letter as far as the amount of water and working time.
You may also want to consider using a sanded grout. I use sanded in just about everything I set including 1/16″ grout lines. The sand prevents the grout from shrinking and holds the size while it fully cures. It’s a bit more difficult to ensure you get the grout lines full but a small price to pay for the piece of mind in my opinion.
Hope that helps. If you have any more questions please feel free to ask.
Hi Roger,
Thank you for all of your advice. Similar to Barabara’s comment (July 12, 2009) I too have a shower floor that needs to be regrouted (mainly around its perimeter, but I’m willing to regrout the entire floor if necessary). The whole floor is not horrible, but mainly the outer edges of the floor are full of mold and it appears that the former owner recaulked over the grout and old caulk without removing any of the old. Also, from what I can see, substandard caulk was used (I’m guessing as a quick fix to sell). My thoughts are, removing the old grout on the floor with grout saw as well as all of the old caulk/grout in the corners and planes (where floor/walls meet). Per your previous comments, I will plan on buying standard unsanded grout (since the lines are 1/8 inch) to regrout the floor. However, should I use grout for the plane areas or should I use caulk? If I should use caulk, could you please recommend the proper caulk to use at the planes as all the recommendations I’m getting from HD or Lowes are to use Keracaulk which is Siliconized Acrylic Caulk (Mastic) which from what I’ve read on the back of the product “is not for use in areas prone to constant water exposure” — ??. When I showed this to the Lowes employee he simply stated “look at the picture, its a shower floor”. HELP!!!!! What’s a girl to do? I’d appreciate your thoughts/insight!
Hi Suzanna,
‘Look at the picture!’
That cracks me up and, unfortunately, is typical of the response of their ‘experts’. Sorry, that just gave me a laugh.
TCNA standards state to use caulk at all changes of plane. That’s just fancy pants talk for ‘corners’. Although I don’t always do that (I’m a rebel like that) you should. I will oftentimes use grout simply because I built the shower from scratch and I know how much movement is likely.
In any wet area ideally you want to use 100% silicone. Be aware, however, any type of caulk you end up using will need to be replaced periodically, It’s meant to be waterproof, not permanent. About every year to 18 months is when I scrape mine out and recaulk.
Now I’m gonna confuse you.
If your grout lines are indeed 1/8″ I would actually use sanded grout for the floor. It would be a better and more durable solution. Not imperative, just a better choice. And without regrouting the entire floor it would be difficult to match the existing. Little more work but it would end up looking better.
You may want to have someone take a look at your shower to determine the cause of the discoloration. If it is, in fact, only discolored around the perimeter that is actually indicative of an improperly draining shower – maybe. Don’t panic
just something to keep in mind. If part of the grout (around the perimeter) still looks wet while the rest is dry that could be a problem with mold, improper drainage, etc.
can a natural slate withstand freeze/thaw on a front porch? red guard? special mortar or grout? whadayado?
Hey Bill,
Slate can withstand the freeze-thaw cycle fairly well as long as you have proper slope for drainage (1/4″ per foot) and there are no spots for standing water. If properly sloped any moisture soaking into the stone would be nominal and no problem.
You can use redgard or, better yet, ditra. Also use a highly modified thinset to adhere the ditra to the concrete and a good unmodified to attach the tile to it. Ditra creates a mechanical bond rather than a chemical bond so you don’t need to worry about the bond releasing due to weather.
thatswatido!
Hope that helps.
Hi Roger,
Here’s a non-ceramic flooring puzzle/issue for you that I’m hoping you might have an answer to. My husband and I are looking at a foreclosure house to buy that clearly at one time had a water issue in the basement b/c the sellers (the bank) just put in a french drain and new sump pump a few months ago. The basement floor is covered with linoleum(or whatever they are made of now) tiles. During our inspection, we started noticing that there was a dark brownish liquid spotting the floor and then realized it was coming up through the cracks between the tiles in places–particularly if we stepped on the edges. Our inspector was at a loss initially and thought it might be that the new drain wasn’t working correctly or that there was a broken sewer line. There was no sewer smell and the liquid had a slightly oily smell and was thicker than plain water. The house was built in 1946. New tiles were laid on top of old tiles. The newest flooring was laid much more recently, but we don’t know when. Later our inspector said that some older adhesives had a tar like quality and if they got wet they could emulsify. Our inspector thought but was not confident that might be the case and since the basement had been wet at some point (hence the drain installation) that these older adhesive take months to dry back out, especially when a newer layer of tile is placed over it. Is it possible that this liquid we are seeing is a liquified adhesive? Does this really happen?
Hi Tracey,
Yes, this does really happen.
Kudos to your inspector for figuring it out. It sounds to me as if that is exactly what is happening. The older adhesives that were around in 1946 were organic based adhesives which required air to dry. The product of choice at that time for basement floors in many areas of the country was a VCT (vinyl composition tile) type of tile. The mastic or glue used to install this was brown in color and did re-emulsify with prolonged contact to water (like a flooded basement).
When this happened it was usually fine to let it set and dry out, which it would do over the course of a week or two, with no lasting problems. The problem you have is that layers of newer flooring were installed on top of this which SIGNIFICANTLY cuts down the ability of air reaching the re-emulsified adhesive below your original tile. The fact that it is an evaporation based curing process for these adhesives effectively eliminates the ability of the floor to fully dry out. When you step on the floor you are forcing the re-emulsified adhesive up through the cracks because there was initially only enough room below the tiles for the adhesive, now it’s mixed with water and the volume can be twice as much as the original amount. There’s just too much stuff under your tile.
The good news, should you choose to look at it that way, is that it is easily removed.
Once this adhesive re-emulsifies it allows the tile to be essentially peeled off the floor in most cases. So yes, it does happen, and no, it doesn’t cause structural damage of any sort to the concrete below it. It should be replaced, though.
Hope that helps.
Thanks, Roger.
I’ll be using the thinset between the joints of Hardibacker, with Redgard over the Hardibacker, and setting the tile with thinset. Hope I’m not stating the obvious, but it sounds like a modified thinset will be ok since it will have time to dry before the Redgard goes on and will be able to dry beneath the tile.
Thanks for your help on this as well as the insulation questions. Your site has been a big help to to someone who didn’t even know what thinset was at the start of the project.
Hey Mike,
The regular modified thinset will work just fine for you.
Glad I could help! If you have any more questions at all please don’t hesitate to ask.
For unmodified dry thinset, the manufacturer recommends using “admix”, which I think is liquid latex, along with the water. Does using the admix negate the good properties of dry thinset mentioned above?
Hi Mike,
Yes, admix is liquid latex. It will not negate the properties of thinset. If it says it only meets ANSI specs if you add the admix I would take it back, that is an inferior thinset. Some companies make thinset that only meet specs if you insert admix, that isn’t what you want.
Also if you are using a membrane such as Kerdi that specifies an unmodified thinset you should not add the latex to it, that effectively negates the reason for using unmodified which is that the latex needs air to cure. When you place a waterproof membrane such as Kerdi over it, it will take forever to fully cure.
If you are using the unmodified for a membrane you should use one of the pricier ones such as versabond and not add the admix.
If you are simply setting tile with it and it does not require an unmodified go ahead and use a modified thinset which has a dry version of the admix already mixed into it.
Just FYI the latex or admix makes the thinset a bit more flexible so the bond does not come loose with regular seasonal changes or heavy traffic. If you are just setting tile I would use a modified thinset.
Roger,
I need to re-grout the bottom of my shower stall, perimeter only, on all 4 sides. The bottom row of wall tiles are coved on all four sides, where they come down to meet the floor tiles. I slowly, carefully & successfully removed the broken grout and vacuumed the 1/8″) grout line. I know how to grout –the issue is that I need so little and I am NOT finding the suitable product that comes in less than a 10 lb. box or bag!…except that I saw this product by Custom Building Products in Seal Beach, CA, in a local hardware store. It contains in this order: Silica quartz, C.A. S. 014-808-60-7, Portland Cement, C.A.S. 997-15-1, and Polyvinyl Acetate Copolymer. Only instruction is “mix with water” and it is called “2SET Tile Repair Mortar.” The only problem is the pound size container lacks any usage statement for or against use on a shower floor, while 99% of the other products, whether at Home Depot, OSH or wherever say “not for use below the waterline.” Just try to get someone on the phone at Custom Building Supply who isn’t chewing gum and sounding like a 14-year old! Email did not work either–they are in need of some web admin assistance! Does this product sound suitable for the bottom of the shower as long as I wait for three days after grouting and then seal the grout lines? I have the tools necessary to install it, if so. Thank you.
Hi Barbara,
The product you are looking at is a tile repair mortar meant to adhere tile to a substrate, not to be used as grout. Other than the color probably being nowhere near what you need, it will not be really suitable as a grout replacement. It will work, I just don’t recommend it. You should be able to find a regular sanded grout in a five lb. box at either Home Depot or Lowe’s that is specifically what you’re looking for at a reasonable cost.
I totally agree with what Roger is saying.
those 2 pails of premixed will cost more then 2 bags of Versabond or another good $15 bag of modified thinset. sometimes it’s just not worth paying more to get something done faster.
mix less dry thinset and mix what you can use.
Hey David,
As long as you are using it in a non-wet area such as a backsplash, wainscot, or fireplace you will be fine. If you’re tiling a shower wall do not use that product. Use regular thinset.
If you are talking about using it on a floor – no, it is not suitable.
Read the bucket, it probably states not to use it for tiles over a certain size – probably 8 x 8. As I stated it would be just like putting the lid on the bucket.
Pre-mixed is easier than mixing. Would you rather save a couple of minutes of installation time or a couple of years of project durability?
Is there no use for premixed thinset? I’m tiling a small area, and a bucket or two of nice premixed latex-modified thinset seems a lot easier than mixing.