concrete and black mastic [Archive] - Ceramic Tile Advice Forums

william hendry

03-31-2002, 12:46 PM

I have removed old linoleum tile, which was bonded with black mastic, from a 30 y.o. concrete slab. I'm debating between putting ceramic tile down or staining the concrete. The floor is way out of level (3/4 in places)and would require a concrete overlay for tile. If I want to stain it leveling wouldn't be necessary, but, in addition to leveling, an overlay would also give me a nice new surface to stain; all without the mess of sanding and solvents. And an inch of concrete would be no problem here.

The "rules" say that to put down the overlay you have to remove all the old mastic to get a good bond. However, several years ago I was in "experimental" mode and put a sand topping mix over a part of this floor and then tiled it. So far, though I keep waiting for a problem to appear, I have seen no evidence of any delamination and the floor seems solid.

I sometimes wonder (a.k.a. worry) if it's because the concrete hasn't really cured 100% yet, or whether the overlay is just "floating" on top. But then maybe the conventional wisdom is wrong. I mean, gee, that mastic is stuck pretty good to the old concrete, what says that it wouldn't stick to the new concrete? Plus, there are concrete resurfacing products out there that appear to be nothing more than latex modified concrete, which are advertised to stick to a variety of surfaces, including asphalt!

What say ye experts?

Bud Cline

03-31-2002, 01:43 PM

S-o-o-o-o.....a-a-a-a.....What's the question?

william hendry

03-31-2002, 01:58 PM

Gee Bud, ya gotta read between the lines. OK, I'll simplify:

1)Can you put concrete overlays down on top of black mastic, ie, will it bond or float?

2)Can you stain an overlay just the same as you would a 4in slab?

Bud Cline

03-31-2002, 02:21 PM

1.)YES and I wouldn't think you want it to bond, I think to float would be more beneficial. I assume your talking "fat mud" here that you would isolate from the slab.

An SLC on the other hand, would bond, but flatfloor is the SLC expert here and can address your questions on that subject.

2.) My "fat mud" installations are for the purpose of setting tile and because of the method used to achieve flatness, the surface really isn't very pretty or suitable for staining.

An SLC on the other hand, would be much pretier and I'm sure stainable. The problem there would be that an SLC isn't intended to be a wear surface.

3.) Well there was no three but I'll add one......
It is possible to "pour" a concrete cap that would be made of either pea gravel or if that isn't possible simply sand and cement. The mix I'm talking about comes straight from the truck and in some places is referred to as grout mix (also). This in my experience requires you to pour a minimum of two inches in thickness and it is finished same as readi-mix slabs.

Rob Z

03-31-2002, 03:15 PM

William

How about a floating mud bed over this mess? John does 'em in his sleep, and can give you a run down on how to do it.

william hendry

03-31-2002, 03:43 PM

Bud -- Hmmm...Fat mud, eh? Interesting. Why that and not a "sand mix"?

Rob -- Are we talking deck mud here (sand + portland) or something with bigger aggregate? And would you put something on the existing slab to insure it floats vs bonds?

Rob Z

03-31-2002, 04:34 PM

Hi William

Yes, deck mud it is. When I do them here in VA, it is usually in basements and I bond the mud bed with thinset to the slab (no lath used). John lays down plastic and lath over the slab, and floats the mud over the lath. The mud bed isn't bonded to anything except the lath, which is floating.

william hendry

03-31-2002, 05:25 PM

Rob -- Couple o' more questions:

*Do you just skimcoat thinset right before you lay the mud?
*Is this polymer mod thinset or does it matter?
*What's the min thickness for a bonded mudbed like you're doing? How 'bout for a floater?
*How do you feel about laying the bonded bed right on the black mastic, think it would bond?

That's more than a couple isn't it.

Rob Z

03-31-2002, 05:39 PM

"Do you just skimcoat thinset right before you lay the mud"

Yes..with a small V notch trowel.

"*Is this polymer mod thinset or does it matter"

Polymer modified is what will stick to the cutback, if anything is going to stick.

"*What's the min thickness for a bonded mudbed like you're doing? How 'bout for a floater?"

I usually go with at least 3/4", although John has told me that I could make it thinner if need be.

"How do you feel about laying the bonded bed right on the black mastic, think it would bond?"

We have talked about bonding to cutback a lot around here. I haven't done much of it. Let's let John give his opinion on this one.

william hendry

03-31-2002, 09:11 PM

OK, I went back thru all the old posts on thinsetting over cutback and I'm satisfied it'll hold. I generally use Laticrete but couldn't find any language in their spec sheets resembling "OK to put it over mastic". Anybody know which Lat thinset OK's this? I've been using Lat 253 w dry polymers in the bag. Any reason NOT to?

Bud Cline

03-31-2002, 09:52 PM

Laticrete 253AU Gold Multipurpose specifically states "for use on non-soluable cutback adhesive".

Your above statement now says "mastic" when previously you stated "cutback"

Now are we talking "cutback" or "mastic"?

I'm g-e-t-t-t-t-i-n-g c-o-n-n-n-f-u-u-u-s-s-e-d again!!!

william hendry

04-01-2002, 04:38 AM

Bud -- We're talking cutback. No confusion intended, where I'm from they call that stuff mastic too.

And BTW, I'm still interested in why you suggested a mix with lime in it rather than deck mud?

Bud Cline

04-01-2002, 06:23 AM

"Lime"? Where did I say that? Am I getting really confused again?

william hendry

04-01-2002, 06:37 AM

You didn't SAY lime, you said Fat Mud; now correct me if I'm wrong but my understanding is that FM has lime in it and that's why they call it "fat", because it's creamy like a tasty food with a lot of fat in it. Here's a quote from John out of another post:

"Finally, the mortar should be what we call "fat mud," not deck mud. Fat mud or brick mortar contains lime to help hold it together. It can be made from sand and masonry cement, or you can buy it in sacks to which only water is added."

So if we agree, I'm wondering what the advantage would be to having the lime in the mud. I know it's used on vertical surfaces because it's sticky but why we don't use it in other "mortar bed" situations as well?

Sorry for the confusion but I'm trying to master all these terms so I'm not confused as I climb the mud learning curve.

04-01-2002, 07:52 AM

HUH? What are you trying to do? Are you setting tile or trying to have a stained concrete surface? Or just preping for another type of floor?

There are special SLC products that are made to be usable surfaces (finished floor)and have very high PSI, and are also made to be mixed with stains. If your interested in those I will post some of them.

However for SLC you need to remove the cut-back..no if and or buts ,it has gotta go. I am not going to recommend attepting to do something that has a less then 50% chance of success.(conservative number)
Some times they might hold for awhile but over time the will start lifting and cracking as the product dries out more. A good bond is essential.

For floating patches and thinsets you have a better chance of staying bonded then with SLC. However every company I know that advertises that you can go over it (this is very over-sold) also says in fine print that it must be wet scraped down to a very fine film.

william hendry

04-01-2002, 09:55 AM

Yes, I guess even I am starting to get confused now. HA! Let's back up a second: From my original post you know that I am debating tile or stain; I haven't decided. Between the issues I'm faced with and the discussion on this thread so far I've pretty much decided that whatever the final surface I'm going to float a mud overlay to fix the existing slab. The question now is: What type of mud?

At this point it seems I have two choices: deck mud or fat mud. I understand using deck mud on a floor as a tile substrate. What I don't know if if it is stainable.

Bud has suggested fat mud as one option. I understand fat mud as a brick mortar or as a mud bed on vertical surfaces. I also know that chemically, fat mud and deck mud are different. What I don't know is if it holds up as an overlay you can walk on and if it will take a stain like "concrete".

Again, at this stage of the game I'm not trying to "do" anything other than assess my options here. That's probably why my original "question" wasn't clear to begin with. I was just trying to provoke a discussion on the topic and in that I have succeeded. (if I knew how to put a grin here I would)

04-01-2002, 01:50 PM

Well if it will make it easier, you can forget about useing deck or fat mud for a finished floor they are just to rough to have any appeal..those are more or less just if you go with tile.

I want you to do a search for "ARDEX" on your browser and check out there line of toppings. Feel free to also contact them and they will explain what you need to do to the floor first as far as prep...They will probably say to wet scrape the old glue and then scarify the entire surface before using it..make sure to ask.
If you use there topping compounds you need to follow their rules to the letter.

their main site that I can't get to load is http://www.ardex.com

just one of their products that I did manage to reach,now they have probably 5 other topping products also..but here is just one to give you an idea if you can get thru there site either.

http://www.concretedressing.com/

I would have posted it for you but their mew POS site jams up my browser/system tighter then a frog a##.

Let us know what you decide or find out.

[Edited by JC on 04-01-2002 at 03:56 PM]

Cami A

04-01-2002, 01:59 PM

I think that this is the link... (http://www.ardex.com/main-products.htm#toppings)

Cool concrete floors...

04-01-2002, 02:51 PM

Yea dats it. Look at the toppings section.

flatfloor

04-01-2002, 06:15 PM

I missed this one.

Most SLCs cannot be stained, further when cured they are very smooth hence slippery (like that hence, Cami?) I would not recommend colored SLCs of any kind.

There are toppings that can be applied to CLEAN concrete and stained.

http://www.decorative-concrete.net

04-01-2002, 07:12 PM

Heres some of the stuff they do.

http://www.designerfloors.com/options.htm

I have seen one of these jobs up close and personal and the colors are very brillient although the look is not my cup of tea..Seems to be more of an industrial look if you ask me rather then a residencial effect. You just can't really get that perfect smoothness and flawlessness.

Bud Cline

04-01-2002, 07:13 PM

william,

You know what? Every day I check in here (usually twice a day sometimes more) and everyday I'm in a hurry. I have home work almost every night estimating what I hope will be future jobs. Then there's my family and the dinner dishes that require my attention.

God help me 'cause summers comin' and I have acres to mow. My wife wants a "bigger" garden this year and my daughters drive automobiles that were created for the children of automotive mechanics not a tile guy.

I live ten miles from the nearest town and have a few neighbors (way down the road) that think all they have to do is to mosey in here on their ATV's on a regular basis and get their free Heinekens and ratchet-jaw about local politicians, the weather, and the price of corn.........

So when I arrive here in the evening and see that there are 18 or 23 or 30 posts I sometimes cringe. I use a dial-up slower than Moses and some visits just end by my falling asleep and crashing into my keyboard while waiting for something to happen in cyber cyber land.

So as I read and type my mind is travelling at "mach seven" while my two fingers are snailing across the keyboard.

So here's what all this is building up to. I now see what you are talking about with my "fat mud" comment. I gotta tell ya, I don't know what the hell I was thinking when I did that, but YOU ARE CORRECT and I STAND CORRECTED.

I have done this here before and I will most certainly do it again. I read my posts that I typed days earlier and I ask myself "what the hells the matter with you Bud"? "ARE YOU NUTS"? And that's with the posts that I wrote myself.

When I find comments supposedly made by me and signed by me but in fact contributed by someone else thru their mysterious magic fingers, I really go insane.

Have you seen the movie "Beautiful Mind"? Go see it....great film. That's what I feel like.

flatfloor

04-01-2002, 09:18 PM

Now, now Bud you'll be fine, just take 2 aspirins and call me in the morning.

william hendry

04-01-2002, 09:40 PM

Hey Bud, thanks for the retraction. I know how you feel. That's probably why I don't give out more advice myself, I'm afraid what will come out of me when I get home after a long day; like right now when it's 11:30PM. Nothing like the freedom that comes from working for yourself; freedom to work 26 hours a day.

william hendry

04-01-2002, 09:55 PM

JC -- checked out ardex, thanks for the tip. They, like some of the other companies I've seen selling micro toppings, say not to go to great lengths to remove cutback other than to make sure it's just a thin film. Check out this article on their site:

http://www.ardex.com/main-guidelines.htm#cutback

04-02-2002, 06:59 AM

Yes that is the skinny on it Henry.

However these companies would rather it not be on the floor at all but they cannot recommend grinding it up due to legal reasons. So basically it is still a fine line even with the "thin film".
Not all cutback has asbestos in it either..but they won't make that call...
Also keep in mind that bieng able to sell a product that can go over cutback is a patch company and SLC companies goal..some of these products are oversold for that reason... I have seen many such claims fail over the years..of course they were blamed for not wet scraping enough..I really don't know..but would still classify it as a risk either way..wet scraping can be a very tough proposition especially if the cutback is sticky.
On the flip side many hold up fine..there are many types of cutback and some have more solvents in them then others etc...

I believe if you did the job and it failed and you put in a claim they will do a core test and if it was determined that the floor did not stick due at the "weakest point" bieng the cutback. your claim would still be invalid bieng that it was not the products fault.

Well now you know the industries position on this and the possible problem you might encounter.

I guess the choice is yours.

You would probably be safer going with tile and useing a good thinset with latex additve I would say as far a failure goes.(after wet scraping of course.)

Also keep in mind these SLC are not cheap either.

How level is the floor and what kinda condition is it in..(cracks)?.

william hendry

04-02-2002, 07:17 AM

Yeah, we're kinda getting back to my original options and good ole' tile is looking simpler by the moment. But IF I wanted stained concrete, AND I wasn't going to remove the cutback, AND I didn't want to try a new fangled, self leveling, resin impregnated overlay, just what type of mud overlay could I put down that WOULD be stainable?

BTW, structurally the floor is in good shape, no cracking, spalling etc. It was just poured by eye I think; somebody with maybe one eye ...... that was mostly looking at a beer can.

stullis

04-02-2002, 09:14 AM

Bud, they have meds for that stuff! :D

William, you would need to pour a concrete cap. Preparation for that??

william hendry

04-02-2002, 12:38 PM

Possibly so Stullis. I say "possibly" because I'm just learning about "concrete" and don't always know the right words to use or what's appropriate for the situation. Would a "cap" mean using a small aggragate mix that might come out of the back of a truck? Or maybe something dryer? If you can educate me on this I would be grateful indeed.

Bud Cline

04-02-2002, 12:39 PM

Bud Cline, 3/31/02: "3.) Well there was no three but I'll add one......
It is possible to "pour" a concrete cap that would be made of either pea gravel or if that isn't possible simply sand and cement. The mix I'm talking about comes straight from the truck and in some places is referred to as grout mix (also). This in my experience requires you to pour a minimum of two inches in thickness and it is finished same as readi-mix slabs."

Now that you have expunged all the possible answers you are going to from this particular board, what are your thoughts?

william hendry

04-02-2002, 12:59 PM

Well, interesting you bring that up because a couple of other sites I ran across in my search talked about "grout mix" as being portland+sand+water in a 1-1-1/2 ratio and worked into the existing slab surface (like you would use thinset) before doing a "pour". In fact, if I'm not mistaken an article I read from the Portland Cement Assoc. shows a picture of a guy brushing "grout mix" into the top of a slab before pouring a cap. BTW, I'll be glad to email it to anyone who would like to read it.

So, now I'm confused again. Is it just that the same name is used for different products in different parts of the country?

Bud Cline

04-02-2002, 01:31 PM

Twenty-five years ago I was pouring caps on existing floors in manufacturing plants and the like. Even did a few outside patios. The product intended to pour two inches thick was always called "grout". I'm not aware of any additives being added back then however there were retarders available upon request.

On occaision a customer would request the addition of some pea gravel. In my estimation this makes it concrete. In fact that's what concrete is in this part of the country today, all pea gravel, no limestone. But back then when and where 2" limestone was the common component, pea gravel still labeled the stuff grout for some reason.

That is unless I was pouring an intended exposed aggregate side walk or patio, then the product was called "pea mix".

So does this type "grout" have other additives that make it grout? Beats me man!

Bud Cline

04-02-2002, 01:50 PM

I think there are several different types of grout intended for different uses.

In another life I "set" heavy machine tools. These machines were always bolted (anchored) to their respective foundations by nuts and bolts. The mounting bolts where sometimes 1" or 1-1/2" in diameter, threaded (high tensile) rod, embedded in isolated concrete foundations.

These type machines actually set on a nut and washer affair that is threaded onto this bolt, then they are held down by another nut and washer. This allows for levelling of the machine within a gnats hair. Once the machine is in its final position the area between the machine leg (which rarely touches the floor) and the floor is then grouted with "machine grout".

Go figure!