Ceramic Floor Tiles - anything we should be concerned about?

Tile is one of the healthiest flooring since you don't need to coat it with with any urethane or the like. It is also very easy to keep clean compared with something like carpet.

The two reasons I would be able to choose it are noise and how hard it can be to stand on it. Noise will bounce off the flooring and it can be disruptive depending on how many people (kids) you have in your home. It can also be difficult to stand for long periods of time (i.e. standing while cooking). Because of this, I will likely end up with cork flooring. If these things won't be a problem for you, I think it is certainly a good choice.

WBisset:

Are you replacing your cork flooring with tile?

If your radiant heating is still in operation, I suggestion you get a pressure test on your heating system before installation of a new floor to make sure that there are no leaks. You would not want to have to dig up a new floor if problems arise in the near future.

Also, you may want to keep extra tiles on hand in case you do need to dig up the floor. Then you will have the correct materials on hand for repairs.

We are also working on replacing our flooring with tile. We are going to use Harrison Tile in Walnut Creek. They seem pretty knowledgeable about Eichlers and seem reasonably priced.

Good Luck!

We currently have cork put in by previous owner 10 years ago. It was dark cork which has faded unevenly by the sun and the cork we have is just butt ugly.

However, we are aware of the two drawbacks you mentioned about ceramic tile - noise and being hard on your feet - and it does concern us a bit going from cork to ceramic tile. I am aware that there are nicer, "higher-end" looking cork out there. If we were to get cork we would absolutely get UV protection on our windows and choose a light color. We are actually willing give cork "another chance" and look at it if anyone has a particular store or supplier or brand to recommend......

We have talked about replacing our flooring for 3 years and really want to go ahead and do it - but we are afraid of making a mistake.

Has anyone considered Linoleum? There is cork in Linoleum (I think) and I haven't seen much discussion about it with respect to radiant heat. Pros/cons anyone? Price compared with cork?

I could be wrong, but I thought that linoleum was a possibly a patented brand name or maybe it referrs to the actual material - but that today what you are referring to is commonly called "vinyl" - am I correct? And "vinyl" comes either by the sheet or in tiles.

I believe that sheet vinyl can be a problem do to the build up of moisture underneath and no way for it to get out. Vinyl tile is fine- but (imho) it tends to look pretty cheesy..... I am not considering it......

Linoleum has been manufactured since at least 1877 and is pretty much made up of "natural" stuff including boiled linseed oil. I think a wide variety of man made flooring materials, including vinyl and asbestos composition tiles, have been generically and erroneously called linoleum.

It is my understanding that old fashioned linoleum is still available. And I believe it is even making a bit of a come back, displacing vinyl and other newer materials in some applications.

Tod- Thanks for the clarification on Linoleum vs. Vinyl. I am also thinking about flooring options and have some linoleum samples from our local flooring shop in Palo Alto. Linoleum does indeed look similar to Vinyl since it comes in big sheets. With Linoleum, we are supposed to wax 2x/yr which doesn't sound too terrible.

I have the following question since I have had a bad experience with vinyl on my current floor. The previous owner put in vinyl in the kitchen and now 5 years later, we see large gray spidering. It appears to be following the cracks in the slab. We have had our slab moisture tested and nothing is out of the ordinary. I assume that that the moisture, although slight, is causing this to occur. I don't want to put linoleum down and find the same problem. My questions are:

1) What exactly is causing the graying underneath the cheap vinyl?
2) If the answer is moisture build-up, is linoleum more "permeable"

My quote for Linoleum is half the price of cork and it would definitely fit in my budget. Linoleum is quoted at about $6/sq. foot ($50-55/sq. yard) where as cork is $13/sq. ft.

Linoleum is different from vinyl flooring. Linoleum is a natural product and includes components similar to your cork floor.

Armstrong carries true linoleum:

http://www.armstrong.com/commflooringna/browse_productcat_dtl.jsp?catego...

We found that linoleum is no cheaper than other flooring materials that, IMHO, have a more upscale look. For a cost similar to linoleum, you could move into a travertine (which some linoleum is trying to mimic).

I understand that the linoleum will also change color with sunlight.

Choosing flooring for an Eichler is not an easy business.

Lynn says "Linoleum is quoted at about $6/sq. foot ($50-55/sq. yard) where as cork is $13/sq. ft."

Do your numbers include installation? Also, if you were planning to put this down yourself, as you know there is big difference in difficulty in laying down sheet linoleum vs. cork tile. I understand that from Barry's article, that cork tile is probably best put down by a professional due to a number of issues....

In terms of ceramic v. cork - at this point I have no idea what the difference in price is for installation, and I have no idea what the cost of the cork tile is by itself - unless Lynn is saying that the cork alone is $13/sq ft. If the material alone is $13/sq ft - that ends that as far as I am concerned!! Eichler flooring choices are definitely complicated and involve compromises. We will not be putting down any flooring ourselves - as a high quality installation is important to me and frankly our talents do not lie in this area! So for any flooring choice I need to add cost of materials to cost of installation.

Jeff, how much is your quote for installation of ceramic a sq. foot????

These prices are for materials and include labor.

Lynn,

I am assuming that the linoleum you are quoting is sheet linoleum???

Is there such a thing as linoleum tile and if so, are you considering it?

What is the range on cork tile price without installation included?

We had lived in Southern California in a house that had about 70 % tile floors. We removed all carpet, vinlyl tile, and wood flooring in our 2.300 square foot 1968 Eichler in Walnut Creek one year ago. We were very pleased with the results. We chose porcelain tile because of the hardness and variation in palate of individual tiles. It is beautiful, easy to maintain, clean, and durable.

The drawbacks are: with shifting of the ground from earthquakes a few tile have had to be removed and regrouted and we had a crack in the radiant heat pipe because of this shifting that required removal and replacement of some tiles. The cost for replacement was very minor and the results were that the floor looked as good as new! Make sure you buy at least five boxes of replacement tile for minor emergencies. We also used Harrison Tile of Walnut Creek.

We love the feel of the radiant heat through our tile floor. Area rugs (persian in our case) on top of this type of flooring produce wonderful color and design highlights.

Michael

Yes- it's sheet linoleum. I didn't realize there was also tile. I'll swing back in to the floor shop next week when I can speak with the owner this time and get some information on linoleum tile. I did a little more searching and found this link about linoleum that has a little more information.

http://www.kitchens.com/Remodeling-And-Design/Products-and-materials/flooring/your-options7.htm

I see that the $6/square foot that I was quoted is on the low end of the $4-22/square foot price they quote on the above link. I would guess the tile was more expensive than the sheet.

No-one has yet addressed the question which I think may be a key one for you - which is - will linoleum tile give you a better result than linoleum sheet around the issue of moisture build up and discoloration on a slab floor with radiant heat. I suspect that it might, but don't really know for sure. The point is moot for me because I am not interested in linoleum, though I must admit that I am curious as to the answer!

Did anyone give you a price range for cork tiles without installation?
Please let me know what price you were given.

I would be surprised if linoleum tiles aren't priced fairly closely to cork tiles- Jeff's email hinted that that could be the case. And of course installation for linoleum tile is bound to be more than for linoleum sheet.......

Thank you for your thoughts, Michael.

You said that you chose porcelain tile "because of the hardness and variation in palate of individual tiles."

Do you think that the hardness difference between ceramic and porcelain tiles is significant for use in a home?

What do you mean by "variation in palate of individual tiles"?

How much was your porcelain tile per sq, and how much for the installation, if I may ask?

I am not "stuck" on ceramic over porcelain at this point.....

Hi Michael: I am completing a total remodel and ready for floors. I am considering porcelain tiles for the whole house and eventually carry the same in the atrium. I am curious if in your installation a anti-fracture membrane was used. I am considering a German product called Ditra that is put over a layer of thin set, ( morter ) then a layer of thin set over the Ditra and then the tile. The Ditra is in between the morter, the idea being that is will not crack as the tile is really on the underlayment. I have talked to several people in the industry last year who have radiant heat and believe that is a good way to go. It does add about $1.50 a square foot to the cost of installation the last I checked. Floors are no easy decision and I so appreciate this discussion. I was leaning towards Kahrs wood floors and now I think the porcelain is in the lead?
Thanks for all the good chatter on the subject.
Lucy

We had a hard time figuring out a flooring material. We researched linoleum tile, vinyl tile, finished concrete, and natural stone tiles (limestone and travertine). We found the pricing for all these items to be similar, for materials and labor.

The prep work for the vinyl and linoleum is what drove up the cost. The installer said that a skim coat would have to be applied to the floor so that the black color of the asphaltic (sp.?) mastic from the original tiles would not bleed through.

We decided to go with the limestone because it looks great, is a natural material, and will transfer the radiant heat well. It won't fade like cork or linoleum. It is a hard surface, but we will have area rugs too.

We will update you once it is installed.

Hi wbisset:

Tile hardness is rated by the Porcelain Enamel Institute. The ratings are called P.E.I. and range from 1 to 5, with 5 being the hardest. You can do a net search and find out descriptions of each of the ratings, and virtually all ceramic and porcelain tiles are rated. For example, we tiled our entire home in 12x12 ceramic tile with a hardness rating of 4 (flooring/light to moderate industrial application).

There are virtually thousands of different tiles out there and it seems, based on my research, that most tile companies only make a given tile for a fixed period of time--always rotating stock to generate new sales.

There is a great deal of confusion about the difference btw ceramic and porcelain tile. Both are made of clay and fired at high temperatures, but porcelain clay is often, though not always, harder and denser than ceramic. They (the "experts") claim that the color goes all the way through for porcelain tiles, while it does not for ceramic. I am not convinced about this, as the color in our ceramic tiles also goes all the way through, but it is certainly easy to verify. The reason to find a tile with continuous color is, of course, in case of chipping or scratching. While rare, it can happen.

Here are the advantages and disadvantages of tile flooring (either ceramic or porcelain):

Advantages:
-Easy to clean and when it is clean, it is REALLY clean! Great for allergy sufferers
-Lasts forever. Should never have to be replaced
-Allows the use of throw rugs for decoration, much like hardwood floors do
-Impervious to water, so a great choice in bathrooms, kitchens, and laundrys
-Nearly impossible to scratch, so is also a good choice for entryways, where small bits of sand or gravel would ruin hardwood floors
-Beautiful to look at and to feel. Gives the home a crisp earthy smell and the look is very compatible with Eichler design
-Rapid heat transferrence, meaning that when you turn on the radient heat, it is warm almost instantly
-Unlike cork or carpet, it will not fade in sunlight (big consideration for Eichler owners)

disadvantages
-Hard on the feet, and for some, the knees and back. If you do a lot of standing in one place (i.e., front of the cooktop or kitchen sink) it is best to get at padded mat of some kind. I have a resturant style rubber one designed to provide maximum cushioning. Hubby and I are fairly athletic but did notice the rather sharp shooting pains in the bottoms of our feet and had to stop going barefoot in the house.
-Everything dropped on it shatters in a million pieces. No kidding. I have learned to be careful about dropping things, as those tiny shards of glass can be hard to find. If you have young kids, this could be a problem. It is also hard on little heads, if you have infants and they are subject to falling
-It does increase the echo in the home, as previously mentioned. If you have various family members, all doing different noise-producing things throughout the house simultaneously, you will notice the difference. Hubby and I got used to it in about a week and don't notice it at all anymore.
-Grout can stain if not properly sealed. For this reason, virtually all veteran tilers recommend a medium or dark grout, if at all possible. Grout should be resealed at 3-5 year intervals.
-Tile and grout can crack, especially if there is an earthquake or your slab settles. The good news is that concrete slab subfloors are the BEST material possible for laying tile over. Always keep extra tiles and be sure you know the brand and color of grout in case you need more down the road, especially in an Eichler, since a radiant leak could mean digging up some tile...

We considered cork (love the look), but found it way too expensive. For tile work, we paid $13.33/ft^2, including the cost of the tile, tear out of old flooring, and setting new tile. That was incredibly cheap and pretty hard to find these days. On the high end, bids went up to $25/ft^2, not including tear out, which no one wanted to do.

A previous poster mentioned a preference for porcelain, due to the nice patterns it made. Glaze styles and platterns are not unique to porcelain--virtually all tiles (ceramic and porcelain) come in every color, finish, and pattern imaginable - this has nothing to do with the type of clay used, only the glaze.

We bought the tile from a wholesaler (highly recommend this as it can save you a ton over retail showrooms) at a cost of $1.13/tile.

Cathye Smithwick

This is a very informative topic!

Hey...one last idea...

Has anyone considered stamped concrete at all? The techniques they use now make the concrete look exactly like stone, tile, wood, whatever! We had smooth concrete poured, stained, sealed for under $6.50/sq.ft., and I don't know how much stamping would add. Just a thought...

Cindy:
I am very interested in what you had done to your floor. At the height of the dot com stuff here I got a price of $18.00 SF to make the concrete look like slate. Did they do any prep work before pouring the concrete? I spoke with three people here who all wanted to bead blast and take the concrete down before doing anything. I would be really interested in the process and if you are pleased with the results. Did you do your whole house? What did they seal it with? How is it wearing? Do you have to keep resealing it?
Thanks, Lucy

Stamping concrete is quite beautiful and does do a good job of imitating the look of tile, though it is quite a bit more porous and rugged looking. I have not seen it used inside, but have seen it nicely done for walkways, driveways, and patios. In this application, it may be safer than tile, since it is rougher and will provide better traction when wet. I know a reputable company here in San Jose that does this. If you are interested, send me an e-mail message.

FYI, there is a concrete surfacing company called Diamond D that is a new supporter of the Network. They are located in Capitola and do gorgeous, refinished and polished concrete flooring. They have done some Eichler kitchens with beautiful results. The owner's name is Dave and he is very responsive. I believe if you go to the third article in my series on kitchen remodeling (posted on this site), you can see a photo of his work.

Cathye

I'd thought I should jump back to my earlier message about linoleum and update you on what I found. If you recall, I mentioned that I had gray streaking on my vinyl and I was concered about the cause and what affect that might have a new flooring that I choose. I was interested in linoleum and spoke with Forbo Linoleum about this.

What they said (and what I suspected ) is that moisture from the slab interacts with the adhesive and essentially plasticizes the adhesive . The resulting dark color bleeds through the vinyl. With anything that requires an adhesive like linoleum, they would like to see moisture emissions as low as possible to ensure longevity.

You can measure this using a Calcium Chloride Test which we had done a year ago. We are running between 5 and 10 pounds of moisture (water) per 1000 square feet per 24 hour period. Linoleum manufacturers want to see between 3 and 5 lbs. They offer a moisture inhibitor product which is essentially like a latex paint to slow down the moisture off the slab for those slabs that emit between 5 and 8 lbs. The flooring store down the street offers this test prior to installing flooring and it sound like a good idea to do this if you have a concrete subfloor like our Eichlers.

At this point since my moisture numbers are high and we can visibily see the problem on our 5 year old vinyl kitchen floor, I would be taking a chance to choose a flooring that uses an adhesive which would include linoleum, vinyl, and cork. Despite the drawbacks, I will be looking at Tile. I appreciate Cathye's summary of tile as well as the others.

For everyone out there please try out stains,sealers,etc. on a sample piece of the same material first to get a true feel for the end product.

wbisset:

The porcelain tiles we choose had a variation in hue and color giving a rich and varied appearance. The porcelain tile, removal and disposal of the previous asphalt tile, and installation ran about $10.00 per square foot.

Michael

Lucy:

The tile work, in our case, involved installation of a membrane on the areas where the slab had cracked over the years. Ditra membrane installation sounds like an excellent way to go.

Michael

Lynn,
thanks for the info on the vinyl tile and moisture. However, don't be too concerned with installing ceramic or porcelain tile. Despite all the potential drawbacks I have not had any issues with sore feet or annoying echoes. I have a 5 yr old and many grandparent visits and I have not had any complaints from them either :>

t

Just to fill in one gap... Usually ceramic tiles are glazed on top over a white or earthtone tile. BUT they also will screen print a pattern on top of a ceramic tile that has a complimentary color. Like make a gray ceramic tile wial a print on top to make it look like Slate.

A couple of points about concrete and tile

1. I am given to understand that with concrete floors any cracks that you have in the slab currently (even if you have them filled) will eventually show up in the finished concrete floor. So you have to be able to live with the idea of some cracking and not be bothered by it.....While grout and tile can crack, my understanding is that it is not as common as cracking in concrete. Also, you can fairly cheaply, replace one or two cracked tiles and the problem will be fixed - don't think it actually can be fixed with concrete....

2. We would consider concrete as a solution, but only if it were relatively cheap compared to other solutions. From what I have heard, once you add in prep, it isn't any cheaper. However Cindy said "We had smooth concrete poured, stained, sealed for under $6.50/sq.ft., and I don't know how much stamping would add. Just a thought..." I know she lives in Southern Cal, but could prices be so different between North and South??? She doesn't say if that includes prep. I didn't get an exact quote, but when I started talking to the concrete folks (don't remember off the top of my head who right now) back almost three years ago, I started to zone out when I was adding up over $10/sq in my head. Because once they go up to that number, I just don't see the advantage to concrete over ceramic/porcelain tile for the same price......We were talking about "polished" concrete - not sure about all the differences....

3. Michael says "The tile work, in our case, involved installation of a membrane on the areas where the slab had cracked over the years. Ditra membrane installation sounds like an excellent way to go. " I don't understand the idea of the membrane installation. How do you know if you need it? Do you have to pull up your existing floor and see how back the cracking is??? And would it still be advisable whether or not the tile is ceramic, porcelain, or even natural stone like limestone or marble????? Is the membrane installed on the whole floor or just the problem areas????

4. Michael, you said "The porcelain tile, removal and disposal of the previous asphalt tile, and installation ran about $10.00 per square foot. " That sounds like you got a great deal!!! If you are in NOrthern California, would you be able to email me with who you used?????

Wbisset:

3. Michael says "The tile work, in our case, involved installation of a membrane on the areas where the slab had cracked over the years. Ditra membrane installation sounds like an excellent way to go. " I don't understand the idea of the membrane installation. How do you know if you need it? Do you have to pull up your existing floor and see how back the cracking is??? And would it still be advisable whether or not the tile is ceramic, porcelain, or even natural stone like limestone or marble????? Is the membrane installed on the whole floor or just the problem areas????

We could tell that some of the rooms wold need membrane installation because we could see cracks in the asphalt tile flooring that was removed. Other cracks with minimal gaps were found after tile removal. Cracks allow seepage of ground moisture I believe - so it is best to seal them. As for your question: do you have have membrane with all tile floors? probably! I would ask your tile contractor to make sure. Membranes as I understand them can be painted on the concrete layer of the floor to create an impervious layer.

4. Michael, you said "The porcelain tile, removal and disposal of the previous asphalt tile, and installation ran about $10.00 per square foot. " That sounds like you got a great deal!!! If you are in NOrthern California, would you be able to email me with who you used????

In a previous post I had mentioned that we used Harrison tile of Walnut Creek.

Michael

I just had our local flooring guy come by and give us a quote on stripping our floor and laying ceramic tile. There has been much discussion about the original asbestos containing tiles and the "cutback" which is the black adhesive that is layered between the original tiles and concrete slab.

My questions are the following:
1. How important is it to remove all of the cutback? Is scraping enough?

2. Others on this forum have used Jasco Mastic remover and others have had luck with Been-e-doo (a soy based mastic remover). Do you also have to scrape? Can someone explain a little more in detail how to use this (ie. pour it out, let the mastic soften, then it scrapes up easier?)

3. What happens if some cutback is left? Do the tiles not adhere as well?

Thanks to Cathye and others who have posted. Your information is helpful. Lynn

Lynn:

The cutback adhesive contains more asbestos (±5%) than the original vinyl asbestos tiles (±3%), so don't scrape it! I recommend the Bean-e-doo by Franmar. It's natural, odorless and works really well. You pour it on, rub it in with a brush, leave it an hour so to work in and soften the mastic and then squeegee it - and the mastic - right off. No sweating required. Try to get the mastic into a paint can and dispose of it as hazardous waste - your county should accept it as it would paint. It's a messy process, but the results are clean. It's actually fun.

It's possible to install ceramic tile over the cutback - previous owners of my house did. I will say, though, that tile adhesive wasn't designed to go over it and it came up fairly easily where it was done in my house. If you want peace of mind, I'd go to the trouble of getting rid of the mastic. You'll know you're tile is adhered well to concrete.

Hi George- I'm all set to try Bean-e-doo. I spoke with Christine at Franmar Chemical. She is sending me a free 4 ounce sample to try out. Their number if 309-452-7526 if anyone else is interested. They don't sell it at any stores in Northern California anyway- you need to order it from them. Thanks for your help. Lynn

The purpose in trying to remove all the cutback is to provide the tile with the smoothest and hardest subfloor possible. This reduces the chance of cracking.

It took us some time to find a contractor that would agree to removing not only the old vinyl, but the cutback as well, in prepping our kitchen floor for tiling. We watched (and helped) with this process and I can only say after doing this, that he was underpaid! Really tough work and I can see why no one wanted to do it. Anyway, there were some small remnants that they could not get up. They were so solid, with no flex at all, that we decided to leave them in place. It sounds like the chemical solution may be a good way to go to get up the remaining stubborn pieces.

Our 1500 ft^2 of tile has been in place for 2 years now with no signs of cracking in either the tile or the grout.

Cathye

Hi George et al- I have another question about Bean-e-doo but you don't have your email posted so I will post the question here. I apologize for keeping this topic going forever but perhaps this will help someone else. It is certainly helpful for me. Thanks also to Cathye for clarifying the reason for removing all the cutback.

I have used the sample Been-e-doo from Franmar and had good results- great! My next question is as follows:

1) After Squeegying up the cutback/Bean-e-do mixture, do you have any recommendations on how to easily dispose of it. Did you soak it up in a rag and squeeze it out into a paint can? Any suggestions on how to keep this as neat as possible are helpful.

2) The Bean-e-doo is a oil based product so Franmar suggests using their "EMERGE" floor and surface degreaser or similar product. What did you use to clean the floor before applying the tile?

3) Additionally I have cracks running through my 1950's slab in addition to smaller chips here and there along the edges of the slab. I assume I just ignore the big slab cracks and fill with the tile mortar and nothing special. As far as the chipping, I was planning on sweeping up the bits and then filling this in with the mortar also. Do you agree?

Thanks, Lynn

George et al,

This is very informative... and scary I must say. I removed the carpet and pad in my master bedroom 2 months ago as I was planning to replace it with Pergo type flooring. There was no tiles under the carpet, however you could see the remnant of them (where they met), all I could find was that cutback adhesive (which I did not know had a name until I read this forum). I am not hypochondriac but after reading these email trails, I am worried. Am I better off having somebody remove the cutback and install the flooring right away. It's been 2 months and haven't stopped sleeping in the bedroom with the cutback exposed... any suggestions would help.

thanks,
David

The cutback adhesive contains more asbestos (±5%) than the original vinyl asbestos tiles (±3%), so don't scrape it! I recommend the Bean-e-doo by Franmar. It's natural, odorless and works really well. You pour it on, rub it in with a brush, leave it an hour so to work in and soften the mastic and then squeegee it - and the mastic - right off. No sweating required. Try to get the mastic into a paint can and dispose of it as hazardous waste - your county should accept it as it would paint. It's a messy process, but the results are clean. It's actually fun.

It's possible to install ceramic tile over the cutback - previous owners of my house did. I will say, though, that tile adhesive wasn't designed to go over it and it came up fairly easily where it was done in my house. If you want peace of mind, I'd go to the trouble of getting rid of the mastic. You'll know you're tile is adhered well to concrete.

All,

I just did some research on Asbestos used in floor mastic. According to the expert, the type found in the cutback is non-friable, which means it doesn't release the deadly fibers easily, they quote "...Conversely, non-friable asbestos containing materials, by their nature, do not want to give up their fibers into the air. This class of materials must be mechanically impacted (power tools such as sanders, drills, chippers, saws, etc.) to release fibers. Asbestos containing flooring and mastics are classified as non-friable materials."

Strangely, they even claim that using a scraper is considered safe (vs. a sander).

Check the following website for more information:
http://w3fp.arizona.edu/riskmgmt/asbestos_flooring_materials.htm

regards,

David

Try looking at Armstrong's VCT tile instead of their linoleum. It's less than $4 a sq foot installed and looks totally original.

We too will be removing our 9x9 tiles and the wall to wall carpeting that his been covering them for years. We, however, will be adding a new radiant system on top of the original and will be sealing it in a 2 inch gypcrete pour. My questions are:

Do I need to get all the mastic up before pouring gypcrete?

Where in SF Bay Area (closest to Palo Alto) can I dispose of the 9x9 tiles?

We had ALL of the original VATiles and mastic removed by a company that is licensed to do asbestos removal.

This company was recommended by TomB and they did a great job. They also did the tile removal for one of the homes on the WG Eichler tour this year.

I think they removed the tiles the old fashioned way - by hand. But the mastic is removed using a machine that essentially steam-cleans the slab. No chemicals involved.

You're left with clean, mastic-free, concrete slab.