lumps in versabond [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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06-09-2004, 11:01 AM
I've been mixing small batches of white versabond to level irregularities in my floor (as was recommended in other threads), but I noticed that there are some lumps in the versabond and it is very difficult to eliminate them all by mixing. I did some hunting around on this site and found a thread about this being due to old/bad thinset.

The next day I can scrape bits of the thinset off with a fingernail. Does this indicate a problem? I made the mixture pretty wet as was advised. But it does seem like I can similarly affect some thinset I used as practice DITRA setting which wasn't so wet and which was done sooner after opening the bag. And it seemed like the custom masterblend also is affected by the fingernail. These last two have had more cure time as well.

So I have three days of work in trying to level this floor and I was hoping to actually set some times this weeked. Do I need to remove all the thinset and start over with a new bag or something? If so, how can I tell if the stuff is good? Also what is the recommended way to remove the existing thinset?

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06-09-2004, 11:58 AM
Hi Adrian,

Do you still have the bag? There should be a date code on it find it and call the mfr then ask what the shelf life is. I hope it wasn't sitting around open for a while, was it?

Gil Smith
06-09-2004, 12:10 PM
You can check the age of the Versabond by looking at the code on the sticker that's affixed to the bag....I don't have one here with me right now but my recollection is that the frist five digits indicate the manufacture date, with the first three being the sequential day of the year and the next two being the year, i.e., 01504 would indicate Jan. 15, 2004. (I could have the order reversed but it's pretty apparent if you look at the sticker). I always check this before I take the bags out of the store.

A Custom rep told me the thinset's supposed to have a shelf life (unopened) of one year from date of manufacture.

As for lumps, I've encountered the same thing and I believe they can be minimized by pouring the thinset powder *into* the water (as recommended by Custom) gradually, and mixing thoroughly as you go, similar to making a "roux" (for you Cajun cooks....:D ). When I get in a hurry and dump the water into the dry powder, I get more lumps. :bang: I've actually put some of this lumpy thinset into a test form and I haven't seen any discernable decrease in strength/hardness, but it makes sense there'd be some adverse effect, however small.

You'll also get what looks like small lumps if you mix the thinset with a rotation higher than the recommended 300 rpm, but in fact it's air that has been "whipped" into the mixture, which can have a decided effect on strength and bonding.

FWIW, unless the thinset is flaking off involuntarily, IMO, there's no problem in laying tile on it, but the pro's may differ. Doesn't seem it could be any worse than the lean mud bed my tile is laid over. ;)

06-09-2004, 01:04 PM
Hi Adrian.

I'm assuming the lumps you speak of are not dry lumps in the bag, but lumps that only occur during mixing. Mixing using an electric drill/paddle has always removed them for me.

Personally I wouldn't worry too much about your fingernail test the day after. Twelve hours or so is not nearly enough time for the thinset mortar to cure rock hard.

06-09-2004, 01:08 PM
The bag was sitting around at least somewhat open for a while.

It looks like there are lumps in the bag that I see as I measure it out. I have been mixing at 140 rpm. My procedure was to add the powder to the water but I am not sure I can claim I did this addition "gradually". I also tried holding back some of the water and adding it later as an anti-lump strategy, but it didn't seem to be particularly successful.

06-09-2004, 01:14 PM
To elaborate, it appears as if there are lumps in the dry thinset. As I pour it out on my scale I see holes in the mound that I presume must be caused by lumps that sink into the mound. However, I didn't actually feel around in it to assess how lumpy the dry thinset was. I assumed that there were like lumps in a bag of flour, but they are not all disappearing during mixing. I am mixing using a "premium" mixer that is made of a thick wire (like 3/8" thick), so it's not paddle shaped. Could this make a difference?

06-09-2004, 01:26 PM
Sneek into the kitchen next time your wife leaves the house and get one'na her wire sieves. Keep those lumps out of the mixing bucket and give it another try. ;)

06-09-2004, 01:55 PM
Actually I'm the one in charge of sieves in the kitchen. Passing 50 lbs of thinset through a sieve would be something of a nuisance. (I'd probably lose a quarter of it onto the floor.) It'd be easy enough to do that for small batches.

Should I be concerned about having had the bag sit around open? To be precise, I opened the bag around 5/16 by tearing a 4 inch hole at the top. And it's been sitting around indoors in air conditioned comfort since then, without any effort made to seal the opening. Should I toss this bag and open up a new one and pay more attention to sealing the bag up?

It sounds like nobody thinks I should be concerned about the thinset I've already applied. Is this correct?

06-09-2004, 02:34 PM
I don't use old thinset nor old grout more than a week old. Just throw it away. The stuff is so cheap, and the financial consequences of using bad thinset so great it just doesn't make any sense to me to run that risk.

Dude, its like $16. Get the stuff at a tile shop or at a fast moving retailer like Home Despot or Blowes.

John from Philly
06-09-2004, 02:38 PM
I am a DIY'er who just completed the tiling process and is ready to grout.

Regarding the DRY Versabond with lumps:
I used Versabond also. I had used the versabond about a month and 1/2 before tiling to do the seams of my Hardibacker. When I returned to do the tiling last week I called the company to ask about the shelf life. The Custom Building Products customer service rep. told me that the bag is OK to use unless there are lumps in it. He said it is caused by water (even high humidity which we currently have been having) causing the thinset to start setting up.

The rep. told me that if it had lumps do not use it. I checked my bag and it was somewhat lumpy ( especially after comparing it to a fresh bag I later bought). My bag had been opened to use it then left opened for 1 and 1/2 months so I bought a new bag and tiled with that. This was with the Versabond "fortified" thinset from HD.

There is a phone # on the bag, call them and go over your issue as I am sure you do not want to rip out the work you did. It may be OK.

06-09-2004, 03:59 PM
When I'm using 2 lbs every couple days over a period of 3 or 4 weeks, a policy of "throw it out after a week" could begin to get a little bit irritating. If it's necessary, I'll do it, since, as you point out, it's not a huge expense. (The biggest nuisance would be hauling the 46 lb bags out to the curb on trash day.) In any case, as I am getting closer to actually setting the tiles I'll be using it faster. I certainly have no issues with tossing the bag in question. The really fundamental issue is whether I should be concerned about the thinset already installed.

I did a careful inspection of the bag of thinset. It is in fact lumpy the way a bag of flour is lumpy. If I press on the lumps they disintegrate into powder.

06-09-2004, 04:52 PM
Adrian, I just finished 17 bags of white versabond last week and found this method of mixing to work best for me.

I put in ALL the water first and then about 1/3 of the required thinset....making a slurry. This makes a soupy easy to liquify mix and then I added another third of the thinset which mixed with the slurry easily and finally the last third brought it up stiff but left me with a very homogenous mixture.

If you didn't get the mix just right, it's easy to add a little water or a little thinset to get the consistency where you want. The powdery lumps you speak of I only had in a couple of bags and they blended right out using this method.

P.S. John's right....Versabond is really good stuff!!

06-09-2004, 05:46 PM
You do have to check the bags in the store before you buy them can tell if they are lumpy just by picking them up most times.....they will actually rattle a bit. The problem I have found is the return policy that HD has. It's great that you can return products, but when it comes to thin set and grout, and they've been in the back of some guys pickup for a week or so, before he returns have to wonder why they bother putting them back on the shelf .:rolleyes:

06-10-2004, 07:10 AM
I opened up a new bag dated Jan 21, 2004 and it had a few lumps in it but they were smaller and fewer than in the bag I've had open.
I tried mixing it as suggested above, by adding the powder in batches, but I'm not sure it made much of a difference as compared to adding the powder all at once to the water. I think I still had a few lumps in there, but not as bad. I did notice that the recommended mixing speed is 150-200 rpm and my choices are 140 rpm and 260 rpm. I'm not sure if being on the slow side makes it harder to eliminate the lumps.

I did call Custom and ask them about lumps. They said that it was OK to use it if the lumps break up, but it does indicate that exposure to moisture has occurred. If the lumps do NOT break up then you're in trouble. They did not have any useful advice on getting a lump free mixture.

I bought a box of screws at Home Depot and realized only after getting it home that 1/3 of the screws, as well as the driver bit, were not in the box. And there was a screw of a different variety in there. Obviously someone returned a partially used box. And let's not talk about what I encountered while looking for a snake for my clogged drain.

06-10-2004, 07:31 AM
I don't think that 'throw it away after 1 week' is realistic for most of diy, a small 5x5 power room took me 3 weekends to finish it and only with half of a bag of versabond. When I mixed thin-set with a blade mixer and a drill, it's 10 times easier than mixing manually, consitantly creamy w/o lumps.
my question is, Do we really need to care about the lumb before mixing it, if there is no lumb after mixing it, why not to use it?

John Bridge
06-10-2004, 05:23 PM
It's normal to have the lumps when the thin set is hand mixed. Don't even worry about it. As to scraping it off with your fingernail, that's normal, too. It takes several days for thin set to get really hard. It has to cure just like concrete.

Sounds like everything is fine.

John from Philly
06-10-2004, 06:12 PM
I am not saying adrian's versabond is bad ( because I have no way of knowing) but Custom Bldg Products told me not to use mine if it had lumps ( When DRY ). I had left the bag open to the air for over a month though and it has been very humid here in PA. I had lumps, bought a new bag @ HD and it was significantly smoother in texture to the bag that was opened.

To answer 30all's question, the versabond will actually begin to set up because of the moisture, in the air or if exposed in another way, and will not work as well.

This is all in reference to lumps in Versabond while DRY, Not when it is mixed.

Good luck

John Bridge
06-10-2004, 06:16 PM
Hi John, :)

I'm not arguing with you. I'm talking about mixing up a soupy bactch of thin set by hand and using it as a leveler. It will form lumps every time. I've done it for years.

I wouldn't use thin set if it wasn't right coming out of the bag, and I don't keep open bags around for very long. :)

John from Philly
06-10-2004, 06:23 PM
I just thought she was saying the bag was lumpy when dry and she went ahead and used the thinset and was concerned with it's quality afterwords .

I did not see where adrian said she had lumps in the wet mix, but mabey I am reading it wrong.

I defer on all points technical and love the site, I just read her problem differently than some others and thought her "dry lump" problem should be discussed because I thought that was her true issue. I had recently had the exact problem and had tech. help from CBP so I passed it on.

Thanks John and I do love the site, it has been a huge help in my ongoing master bath renovation and I even have your book. No arguing from my side ,very sorry it came off that way.

John :)

06-10-2004, 10:56 PM
Do you slake your mix? After you have it mixed, you should let it sit for 10 minutes and then remix. (This is called slaking.) The sitting time lets any dry lumps absorbe a little water so they mix up when you remix.

For mason's mud (fat mud) slaking also lets the lime start "working" so that the mix becomes sticky. I don't know if thin set has lime in it or not. I mixed my thin set about the way duraleigh said (adding the powder in thirds), then let it set and then remixed it. It was very smooth and easy to work. If you mix is a little dry you can add water when you remix, but I would not add more dry mix.

The bags are moisture resistant, once you cut it open the clock starts, there is probably nothing you can do to keep it from going bad in a week or two.

I go through a lot of masonary cement doing stone work but sometimes I let it set while I do other work. If I see lumps when I dump it in the bucket the bag goes in the trash. I am a DIY and I probably waste a lot of cement this way, but that's the price you pay for doing the work slowly in your own time. And the stuff is cheap, so its not that big a price.

06-11-2004, 07:11 AM
I started out with dry lumps in the bag. They were soft, lumps that would disintegrate, but they didn't all vanish in the mixing, so I ended up with some lumps in the wet mix too. Even the brand new bag had some lumps, though a lot fewer and small than the bag that sat open. Custom told me that if the lumps were soft and turned to powder easily then it was still good. If the thinset was full of "rocks" then it was bad, according to Custom's tech support. In any case, I'll play it safe and not use the bag that sat around open. But even the new bags seem to have some lumps.

Now I have been letting it slake but I haven't been seriously mixing it after that period. (More like swirling a trowel through it a couple times.) Should I be really seriously mixing it again after the slaking period?

John Bridge said "Sounds like everything is fine." Thanks for the evaluation. I'm planning unless I discover something alarming tonight to declare it "flat enough" and lay the DITRA tomorrow. Then kerdi-band, and then I'll actually be able to set some tiles! (I'm at week 7 in the project and I had advertised to my wife that it wouldn't take this long....:D) It's actually convenient that the thinset is kind of soft the next day at least for this leveling business, because it means it's less work for me to remove the excess thinset I've been ending up with in various places. I also have noticed that it definitely gets harder in another day or two and the bag does indicate a 28 day cure time.

'm mixing it using a drill at 140 rpm. Is this considered "hand mixed"? This definitely does a better job of lump elimination than mixing it by hand with a trowel which I have also done for some of my small batches.

06-11-2004, 08:24 AM
Use a colander instead of a sifter if you have lumps and need to mix up more than a couple of handsful.

06-11-2004, 10:17 AM
I always remix any mortar type product after slaking. I use the same mixer I used to mix it originally (a slow speed 1/2 drill) and mix it for about half a minute to one minute. I consider that a "serious" remix.

I have never tried any other way of mixing and I am happy with my results. But, I am curious what the pros do.


John Bridge
06-11-2004, 07:52 PM

This pro, or at least this pro's helper, won't dirty up his paddle for less than a full 5-gal. bucket of thin set. :) Most guys use a margin trowel to mix very small quantities of mud. You can also use a 1x2 about 3 feet long. We have one of those we carry around on the back of the truck. :)

06-12-2004, 12:04 PM
I was using a small trowel to mix batches of 1 lb, 2 lbs and 4 lbs, but when I got to an 8 lb batch I went to the paddle, and it seemed enough of a savings in time and effort that I used it for my next 4 lb batch as well. The big savings is in lump elimination, which seems to mean an endless period of squishing lumps with the trowel.

In any case, the DITRA is down. Kerdi-band next, then tiles!

06-12-2004, 09:21 PM
So, what exactly happens when thinset goes "bad?" If the lumps disintegrate when mixed, even if the open bag has been sitting around for a year, you still can't use it? Just curious what exactly the problem might be :cool:

Gil Smith
06-12-2004, 11:07 PM
Carla, here's a thread on the subject:


John Bridge
06-13-2004, 02:40 PM
I don't know the science behind it, but there are two ways cement products go bad: one of them is where the product becomes hard or rocks form in it; and the other is where it remains powdery, but it won't set up properly after it's placed. I'm thinking specifically about grout that is placed and then a month later you can scratch it out with your fingernail.

In any case, cement products are relatively cheap, and labor is dear. It just doesn't pay to take the chance on stuff that's been laying around. I keep partial bags of grout a few days just in case I need to do a touch-up. After that they go on the back of the truck and ultimately to the sanitary fill. :)