Unmodified Thinsets – A User’s Guide

by Roger

In my previous post about thinsets I explained what modified thinsets are and how they came about. That post actually started out as this post, I tend to get sidetracked by beer my dog.

Unmodified thinsets, in one form or another, have been around forever. With the expanded use of modified thinsets, the unmodified version had nearly gone by the wayside with everyone except us hard-headed setters who bought unmodified thinsets and added liquid admixes to them – to create modified thinsets. I no longer do this for my modified thinsets, but it was a hard habit to kick. :D

The reemergence (I know – doesn’t even look like a word) of unmodified thinsets came about in November of 2001. At an NTCA / Schluter workshop the statement was made that the preferred method of installation over ditra is the use of an unmodified thinset.

Mass confusion ensued.

This has continued to this day with even seasoned professionals questioning if unmodified should be used, and if so – why and which unmodified to use. This problem is compounded for do-it-yourselfers who don’t have nearly the understanding nor material and product access that we do. It’s difficult to find and purchase. If it helps, it’s sometimes difficult for us as well.

So let’s see if I can shed a little light on the subject and at least let you know which ones to look for and where. This list WILL be a bit biased. If you’ve read anything here you know I’m a Laticrete diehard. It is, and will continue to be, my preferred manufacturer for nearly every tile and stone setting material needed. That said typed, I do realize that other companies exist. :D

Just like modified thinsets, there are different levels or grades of unmodified thinsets. This is normally measured by the ratio or percentage of cement to sand in the mix. The higher the cement content, the better the thinset. More cement, more sticky, more stable.

It is also, in part, due to the type and percentage of whatever retention product is in the mix. For most thinsets (as far as I can tell – ancient guarded secret and all…) a powder called ‘hydrated lime’ is used. It is the same lime used by brick masons in order to retain water in the cement mix for a longer period of time, thus making the cured product stronger.

So that’s how unmodified thinsets are ‘grouped’ or graded – the ratio of those three items in the mix. Now that you know that, let’s group them in order according to how they are graded and perform. I’ll do this by manufacturer since most people only have one or two specific brands available.

Laticrete 317

Laticrete 317

Laticrete:

Laticrete 272 is considered the premium (best) – then Laticrete 317. There is negligible difference in these thinsets unless an admix is added to make them modified. For use as an unmodified I prefer the 317. Although they classify the 272 as their ‘premium’, they’re nearly identical.

The difference in these two thinsets: “There is more portland cement in LATICRETE 272 and the sand in the

Laticrete 272

Laticrete 272

LATICRETE 272 is slightly finer so it is a little bit creamier.” (Thanks to Anita at Laticrete for this clarification) The 272 contains 25-35% portland while the 317 contains 20-30% portland.

On the consumer side Laticrete products often have a different name – you may be familiar with Laticrete MegaBond. That is nearly identical to the 317. I use 317 for almost all of my unmodified thinset needs.

Mapei kerabond

Mapei kerabond

Mapei:

Kerabond: This is considered Mapei’s premium unmodified thinset. It works very well for any Schluter product

 

 

 

 

 

Mapei Keraset

Mapei Keraset

Keraset: This is Mapei’s mid-range unmodified. It’s not ideal but it works if it’s the only available. Give it extra time to fully cure! If you use Keraset be sure to wait a FULL 24 hours, at least, before the next step.

 

 

 

 

 

Mapei keraflor

Mapei keraflor

Keraflor: The ‘economy’ level unmodified from Mapei. I would not recommend using it for any shower applications or any regularly used flooring surface over ditra. Best to find one of the other two.

 

 

 

 

 

Custom Uncoupling Mat Mortar

Custom Uncoupling Mat Mortar

Custom:

Uncoupling Mat Mortar: This is Custom’s premium unmodified mortar made specifically for Custom’s spiderweb mat and other ditra-like products. It is difficult to find and has limited availability. If you can get your hands on it, use it.

Masterblend: Currently Custom’s only readily available (to my knowledge) unmodified thinset. It is available at most Home Depots. It’s a good sack of powder if you have a flood and need a makeshift levy. That’s it. Any reputable tile contractor will tell you not to use this for anything – ever. I’m one of them. The only really good thing I can say about it – It is an unmodified thinset.*

Custom masterblend

Custom masterblend

*This is by no means any type of intentional slander or slam against Custom building products! They make some great products. Masterblend, however, is not one of them in my opinion. And that’s all this is – my personal opinion. I do not consider this a viable product with which to install tile or stone over Schluter products.

 

 

Tec SturdiSet

Tec SturdiSet

Tec:

Sturdi-Set: Tec’s premium unmodified. A good unmodified thinset for nearly anything requiring one.

 

 

 

 

Tec full set plus

Tec full set plus

Full-Set Plus: Tec’s other unmodified. Comparable to a mid-range unmodified. It’ll work in a pinch if needed, but ensure full cure time before the next installation stage.

 

 

DitraSet

DitraSet

Bostik (Hydroment):

Ditra-Set: This is the best product with which to set anything over kerdi or ditra – it was specifically manufactured for that purpose. The availability is extremely limited, however. Most professionals don’t have ready access to it, let alone regular homeowners. So just plan on not finding this.

If you are lucky enough to find it you’ll feel ecstatic, like the luckiest person alive! If you don’t find it you’ll just think ‘Well, FloorElf told me I wouldn’t find it…’. See – win-win for me. Yay.

So in the groups above it breaks down like this:

Best:

Bostik Ditra-Set

Laticrete 317 (Laticrete MegaBond)

Laticrete 272

Mapei KeraBond

Tec Sturdi-Set

Custom Uncoupling Mat Mortar

Works if limited options exist:

Mapei KeraSet

Tec Full-Set Plus

It’s last call – find something:

Mapei KeraFlor

Go home alone and hold onto your wallet:

Custom Masterblend

So there you have it. The most commonly available unmodified thinsets and where they rate on the scale of quality. As I stated, this list is biased. The list above is the order in which I would use them if given the choice. Regardless of the order under each heading (Best, Works, etc.) this is how they are rated by their respective manufacturers.

Do not be surprised if you cannot find one of the quality products easily. They are not commonly stocked by regular big box stores except for the Laticrete Megabond. The best place to look for any of them would be at a tile supply shop. If, however, you are limited to normal big box stores, you can find some of the common products there.

Lowes will either stock Laticrete or Mapei. Home Depot will only (currently) carry Custom products. Menards normally stocks Mapei. Beyond those three, I have no idea what you may have around you.

You can always check the respective company’s website to find the nearest supplier. Since you will be looking for one of the more uncommon products keep in mind that just because you have a supplier near you does not mean you’ll find that particular product there. It’s always best to call the customer service line and ask them directly where you can buy the product you want.

One last thing – before anyone asks: adding more portland cement to a particular product may or may not make it better. Adding more cement to masterblend, for instance, will not make it comparable to kerabond. It doesn’t work like that. These thinsets, as all tile installation products, are put together in specific ratios in order to accomplish what the company wants. It may work, and it may not work. Unless you personally know someone in the chemistry department of the manufacturing plant there is no accurate way to tell.

ANSI Specifications

All thinsets, as well as any tile installation product, will have a specific ANSI (American National Standards Institute) number on the bag. This determines what type of product it is and what ANSI standard it meets. The number for unmodified thinset is A118.1. The ‘.1’ at the end determines the unmodified version. If you find a thinset you are curious about, and it is not on this list, look for that number. If it has A118.1 AND more numbers after that (with no mention of admix) then it is a MODIFIED thinset.

For instance, if it says on the bag that the product meets ANSI standards A118.1, A118.4 and A188.11 then it is a modified thinset. All modified thinsets meet the criteria set forth for unmodified thinsets as well, that’s why the A118.1 is on there.

ALSO! (I know it’s a pain, I live it) Most bags of UNmodified thinset have the A118.1 number as well as the A118.4, possibly A118.11 also  If it does it will plainly state that it only meets the last two standards (for modified) when mixed with the appropriate admix. Masterblend states that it meets all three – with the addition of admix (liquid latex). Don’t let this confuse you. They cannot legally misstate the ANSI numbers.

I hope this helps clear up a little bit of confusion about these products and helps you determine which would be appropriate or best for your project. As always, if you have any questions please don’t hesitate to ask them below. I answer them all. I’m just super cool like that. 8)

 

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Ron

So according to your reply to Matt, when I back-butter a tile, I am suppose to spread it real thin, so just the recesses in the pattern on the back are filled? What about marble or granite tile that is flat on the back? Does not matter now, but I laid a floor and was back-buttering the marble tile the same as the floor, then when I set the tile, the rows on the floor ran 90 degrees to the ones on the tile. The marble was green, and I was afraid of the serpentine mineral in it, so I was using epoxy mortar to prevent curling. You don’t want to know how much of that pricey epoxy I went through. Anyway, for future reference can you explain back-buttering for me? Thank you.

Reply

Dita

Much confusion indeed!
We’re in the middle of a Kerdi bathroom installation. Our supplier recommended Ardex 4. A modified thin set, but we stuck to the Schluter recommendation for unmodified. We found (you guessed it) Custom Masterblend at Home Depot and have used it to seal the wall seams and the washers. It looks and feels WRONG, so tonight we have found your article, and wonder what is the best way to remediate what is already done.
Should we find a better thin set and continue, or can we scrape off what we’ve done and hope that the Kerdi isn’t damaged? We are on Vancouver Island. According to our internet research, the nearest Laticrete is 100km away, the nearest Mapei is in Bellingham, Washington. Is modified thin set over Kerdi really a bad idea?

Reply

Roger

Hi Dita,

I’m about to confuse you more. :D You want to get a better thinset and continue, but you can use the Ardex 4. Ardex is approved for use over schluter products. You really probably don’t want to hear the technicalities, but you’ll be just fine, and your warranty will remain intact, if you use the ardex.

Reply

Dita

Thank you for the reassurance Roger. You suggested that I could continue, using the Ardex – does that mean that the tiles aren’t likely to pull of the wall when installed over the Kerdiband patches that were already applied with inferior thinset, or should I scrape them off and redo with Ardex?
You comments are much appreciated.
Dita

Reply

Matt

Roger,
Great site…it has gotten me a long way on my first tiling project. A few questions here.

1) I did the full Schulter Kerdi for the walk in shower. Used Kerabond for membrane, walls and floor. I bought the Keralastic latex mix to make the Kerbabond modified for the ceiling (no kerdi on the ceiling, just greenboard). My tiles are heavy 24″x12″ porcelain so I wanted the ceiling to be extra strong. I have run out of the keralastic for the last 2 half tiles of the ceiling 24″x6″ that will be above the shower door. Is it okay if I use plain unmodified Kerabond (w/ water) so I don’t need to buy another $70 jug of keralastic latex mix for the last few inches?

2) I haven’t laid the 1″x1″ mosaics for the shower floor yet. Any advice on best trowel for such small tiles so the thinset doesn’t come up the sides too far but is also thoroughly attached?

3) The rest of the bathroom floor has a Ditra-like membrane from a company called Protegga. Its all I could get up here (Im in Calgary). Even though it looks identical to Ditra, its instructions call for using modified thinset for the tile. Do you seen any issue if I just treat it like Ditra brand and use unmodified Kerabond instead?

4) For the bathroom floor tiles on the Ditra (or Protegga), how thin/thick should I be back buttering? Tiles are also 24×12.

Thanks soooooo much for already getting me this far!

Reply

Roger

Hi Matt,

1. Yes, that’s completely fine. I’ve hung bigger tiles than that on a ceiling with unmodified.
2. I use a 1/2″ u-notch, then flatten the ridges with the flat side before installing the mosaics. I end up laying them in a flat 1/8″ bed of thinset.
3. No issues at all. It works the same way.
4. If you use a large enough trowel you only need to skim the back of the tile to ensure all the pores and little squares (or whatever raised design is on the back of your tile) are filled with thinset. That’s what I mean by backbuttering.

Reply

Gaston mimeault

Hi
Your information us very interesting
Fan Kerabond plus be je use to install ditra Heat menbrane
Tanks
Gaston Mimeault

Reply

Roger

Hi Gaston,

Yes it can.

Reply

Bob

Can / should I use Mapei Kerabond to install Porcelain tile over Ditra? Their website seems to indicate using Kerabond “T”. I have already purchased the regular Kerabond….
Thanks!

Reply

Roger

Hi Bob,

Regular kerabond is fine.

Reply

Craig

Hi Roger, I am dealing with neolith, The Size, large 4’x4′ tiles 6mm thick that has a fiberglass scrim on the back and is being installed on a large interior fireplace. The heat n glow fire place has a warning lable on it that say’s “due to high temperatures, recommend using unmodified thinset when applying tile. The Size recommends using “2 component, highlyflexable class C2 products according to EN12004”. I’m trying to find a thinset that meets both requirements. Any suggestions? Thank you.
Craig
Custom Stone

Reply

Roger

Hi Craig,

There is no thinset that meets both. I wouldn’t worry too much about the non-modified requirement, I would use the c2 thinset for those particular tile. It’s required, a non-modified will not work on a tile with any type of fiberglass reinforcement on the back.

Reply

Craig

Thank you, I will definitely use mortified everywhere I can on job. Another product I’m looking at is bonstone t2000 epoxy for the tile around the fireplace.

Reply

Rick

Custom’s MegaLite will stick anything to anything, handle large format tile, and provide flex to deal with substrate and/or tile movement that’s probably going to occur with large temperature swings. It can be applied up to 3/4″ thick if needed and it’s also very light at 60% of the weight of normal thin set for the same volume. The downside is it’s pretty pricy. I’ve been using it to install porcelain 18×18’s on an exterior waterproof membrane, and it’s likely going to be a “go to” product for challenging applications. :dance:

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Mb

I just had porcelain wood floor tile installed. 12 yr old house concrete slab. Was told thine had to be adjusted constantly because tiles come uneven and my floors are uneven. The floors feel uneven. And a lot of lipage not higher than a dime though. Grout looks horrible gray with mahogany tile. All stains put on grout come out gray. I want it to look natural. Any problems here!?

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Roger

Hi MB,

It sounds like there are a lot of problems there. I don’t understand what you’re asking me.

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TanToes

No. Water test (every rain and hosed down by me) is definite flodd test it slopes….to the end it can’t run out of.

What cement type ‘stuff’ do you recommend I slather on deeper on the flooded end? Slanting it toward where it can on opposite end?

Reply

Roger

Deck mud.

Please respond to the previous answer if it’s the same subject (click on the ‘reply’ link when you hover over it). I have (literally) over 30,000 questions on this site, I don’t memorize them all. I don’t have the time to go searching what is being asked from a previous answer. When you use the reply link it references that for me when I read your question. Thanks.

Reply

TanToes

Hi Roger….shower finished. Next project which I may do or only need to hire done is tiling ‘lanai’. No freezing where I live and it doesn’t get terribly hot through one side of screen.
But settling. Hopefully most of that over in a 15 year old build. Water runs to front left corner and needs to go to front right to run out. What steps and what products over unpainted slab to make it a definite slope that way?
(One problem at a time.)
Thanks for your holding all of our clammy hands through our projects.

Reply

Roger

Hi Tantoes,

It should already be sloped. All you need to worry about is a substrate membrane. I prefer ditra.

Reply

Kevin

Hi Roger,
I am installing porcelain tile on Ditra on my exterior deck which is over a bedroom. Laticrete 317 floor & wall un-modified thinset was recommended. I noticed on the bag that adding either 3701 morter admix or 333 Super flexible additive was recommended for exterior use on porcelain tiles. Will this work with Ditra or just adding water work as well for my exterior use? Thank`s,
Kevin

Reply

Roger

Hi Kevin,

Adding admix creates a modified thinset. Regular unmodified with just water will be fine.

Reply

John De Pinto

Hello,
Please inform me on which is the absolutely best product to use on my concrete slab basement floor, before installing porcelein tiles : Ditra, Mapelastic AquaDefense, or Mapeguard 2. Do any have also vapor qualities?
Also, my installer mentioned a “White Ditra” product he used. Is this considered a quality product, and who makes it? I hear it is cheaper than the orange Ditra and is it good on a concrete slab?
I would appreciate an answer soon, as the installers are starting soon.
Thank You for you help,
John

Reply

Roger

Hi John,

I prefer ditra, yes it has vapor management properties. The ‘white ditra’ is likely stratamat, made by laticrete. It is a VERY good product and I use it a lot as well. It also have the vapor management – ideal for your installation.

Reply

Sylvia

I had a bad tile job about 1/3 of shower is done.
I want to take off the porcelain and glass mosaics off.
Without smashing them, any other suggestions?
I’d like to save the kerdi membrane behind it but I can replace that if needed.

I need to give the new contractor a place to start.

Reply

Roger

Hi Sylvia,

Get a drywall knife and you should be able to ‘sheer’ the tile off the kerdi with that. Just work it between the tile and kerdi.

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John

Roger, great info here thanks for that. But, I just wanted to let you know that from TEC’s website that they list their Full Set Plus as a Premium mortar and they don’t seem to acknowledge Sturdi Set anymore, only the Uncoupling Membrane Mortar. Do you have any comments about the uncoupling mortar, with a ditra underlayment?

Reply

Roger

Hi John,

They’ve recently changed their unmodifieds. The uncoupling mortar works very well.

Reply

Jo

Hi there,

Just found this site – awesome!! Question for you. The original owner of our house had carpet in the master bath. Don’t ask. :P Anyway, we want to remove it and replace it with laminate. We know (believe?) we’re supposed to use thin set on the sub-floor (this is on the third floor of our house, not on foundation), but since we have carpet right outside the bathroom, we think we’re supposed to put something on the carpet, or bordering it, to prevent the thin set from leaking to the carpet.

Any advice on this? Also, do you have a tutorial for the typical homeowner (desk jobs) in this process? Or any advice? :)

Thanks for any help,
Jo

Reply

Roger

Hi Jo,

When installing laminate flooring you do not need thinset beneath your substrate.

Reply

Tod Collins

There is quite a bit of discussion on thinsets on the web particularly in reference to the Schluter products. Using the Schluter shower system, Schluter suggests an “appropriate” thinset under the shower base for the substrate” but really doesn’t explain further. Mine is plywood. Would that be modified or unmodified between the Schluter shower base and plywood substrate?

Reply

Roger

Hi Tod,

Yes, modified over any wooden substrate.

Reply

Tod Collins

I’m finding it difficult to find a supplier for Laticrete products locally and I live in your backyard. I’m assuming your able to buy direct because of your volume. Any suggestions for a tiling wannabe? Mapei is available at one of the local stores but not Kerabond specifically (order only) unless it’s marketed under another name.

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Roger

Hi Tod,

I have to drive down to design materials in Denver to get it. It would likely be easier to order the kerabond.

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Greg

Lots of great info on this site, thanks for all the info….

How bout a list of you favorite modifieds and modifieds to avoid? Too many variables? Just wondering…. If not I’ll just have to make the hour drive and get the laticrete stuff since in seems to be one of the better companies out there and one your favorites.

Reply

Roger

Hi Greg,

Anything laticrete is good in my opinion. Mapei thinsets are also very good.

Reply

Dustin

Do you have the TEC mortars mixed up? On the TEC website they portray the Full Set Plus as their premium unmodified, and the Sturdi-set as the entry level..

“TEC® offers two reliable products: the Sturdi Set™ Mortar and Full Set Plus® Mortar. A premium unmodified mortar for installing tile, Full Set Plus is an ideal product for projects that require a high-strength, quick-grab formula for non-porous and semi-porous tile.”

“An entry-level, thin, dry set mortar, Sturdi Set mortar is capable of working on most tile installations over cementitious surfaces. “

Reply

Roger

Hi Dustin,

Nice catch! :) However, when dealing with ditra or kerdi the Sturdi-set cures stronger and more quickly than does the full set plus. It may have something to do with the full set being a ‘premium’, but in the context of schluter products it is my experience that the Sturdi-set is more along the lines of a premium for that particular application.

Reply

Maz

Hello Roger,
You might have answered this question, if so my apologies. What product would you recommend ( unmodified thinset/midset ) for 18×18″ porcelain tiles over Ditra and/or Ditra XL?
Thanks,
Maz

Reply

Roger

Hi Maz,

Unmodified thinset is required between ditra or ditra xl and tile.

Reply

Renato

Out of curiosity, what would be the recommended products from Mapei when using Kerdi for waterproofing (on cbu substrate) to adhere 2cm marble slabs in shower walls (sometimes 6-7ft tall):

– i assume Kerabond to adhere Kerdi to CBU
– Recommended thinset or epoxy to adhere stone to Kerdi?

This would be for a very high end project. In addition:

– Recommended mud bed product from Mapei to lay over PEX radiant tubing
– Ditra over mud bed recommended?
– Thinset recomendation for 2cm stone on floors from Mapei

Its basically a 45k sq ft mansion with 2cm flooring and walls in most rooms and we are going with Schluter and Mapei products so any extra recomendationts are welcome. Im not involved on the installation myself but the company i work for is so im curious.

Reply

Roger

Hi Renato,

Kerabond for everything. You can also use epoxy on the walls over the kerdi, but it’s not necessary. Same with the floor – kerabond. I have no idea about a ‘mud bed’ product, I don’t know what mapei has and I always mix my own. Any premixed deck mud product they have would be sufficient. Yes, ditra or a mud bed is bulletproof.

Reply

Renato

Thanks Roger! Much helpful.

I’m pretty sure we can also use a rapid-set system like Granirapid from Mapei for large 2cm panels on Kerdi walls correct? Since it’s cures fast, it should not be a problem from my research.

We are also running into problems with floor height, since GC is using 5/8″ tubing on floor with clip. This is an old early-1900’s built school that’s being renovated into a home. 100 year-old concrete subfloor for all floors (2 floors + basement). Is it safe to have 1/2″ minimum modified mud over the tubes (1 1/4″ total), then ditra over that, ~ 1/4″ thinset, and 2cm stone panels over everything? Debating that right now with the GC/architect. Appreciate the response!

Reply

Roger

Hi Renato,

Yes, you can use rapid set. However, you CAN NOT have a buildup of mortar that thick. You need either slc or deck mud over those tubes and clips.

Reply

Nel

Hi,
Last night I posed a convoluted question about making my own modified thinset. Please ignore, it will be more cost effective to buy a bag of Laticrete 4XLT instead.

Reply

Roger

Okay. :)

Reply

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