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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Scott mahaney

Hi Roger,

I am a relative novice but I have done some remodel and set (tv/movies/exhibits) tiling. I am doing a custom shower now.

I have set some 1″ hex mosaic on my pan and had to use too much mastic for adhesion.
A bunch came up between tiles. I got some out while curing (using the handy multi tool!), but there are areas where it is still heavy. There were areas that were taped together prior to installation and the tape remained during setting that have the mastic flush with the tile.

I know I’m in for a lot of manual picking but is there anything that will make the job easier? Wetting the tile a bit?
I experimented with a triangle grout removal tool but it is too hard on the tile edges.

The grout line is nominally 1/8″, with many down the nearly 1/16″ due to pan slope.

Any advice you can give would be great!
Keep up the good work and thanks for all the cool tips!

Have a great day,
Scott

Scott Mahaney
:bonk:

Reply

Scott mahaney

Hi Roger,

I am a relative novice but I have done some remodel and set (tv/movies/exhibits) tiling. I am doing a custom shower now.

I have set some 1″ hex mosaic on my pan and had to use too much mastic for adhesion.
A bunch came up between tiles. I got some out while curing (using the handy multi tool!), but there are areas where it is still heavy. There were areas that were taped together prior to installation and the tape remained during setting that have the mastic flush with the tile.

I know I’m in for a lot of manual picking but is there anything that will make the job easier? Wetting the tile a bit?
I experimented with a triangle grout removal tool but it is too hard on the tile edges.

The grout line is nominally 1/8″, with many down the nearly 1/16″ due to pan slope.

Its Mapei kerabond, if that helps.

Any advice you can give would be great!
Keep up the good work and thanks for all the cool tips!

Have a great day,
Scott

Scott Mahaney

Reply

Joanne

Did you receive my questions?
I’m not sure they went through …

Reply

Joanne

I recently purchased a house that was built in the mid 1970’s. When the shag carpeting was removed, we found a layer of fiberboard directly underneath it and then a layer of plywood underneath the fiberboard which sits on the floor joists. My renovation person is aiming to tile the house with porcelain tile. It was recommended to her by a tile store in Tucson, AZ to use Spider Web II (now Redguard) Uncoupling Mat sandwiched between two layers of modified thin-set. The tile store is recommending using Custom Building Products “Versabond LFT Professional Large Format Tile Mortar” (modified dry-set mortar, which is a proprietary bland of Portland cement, inorganic aggregates, copolymers and chemicals). I am chemically sensitive and have concerns about whether modified thin-sets would be safe for me (though once they are be buried under tile and grout that is sealed, I don’t know that that would be an issue). At any rate, the tile company says that, given a description of my situation (my house, my floor, etc.), the modified thin-set would do a better job of preventing the tile from having problems (cracking, etc.) than a non-modified thin-set. If I feel like I need to go with a non-modified alternative, the one they suggest is Mapei “Floor Tile Mortar.” Of course, the other situation I am confronted with is whether I can safely and effectively waterproof the (MDF?) fiberboard with something that the thin-set will safely and effectively adhere to. My renovation person is suggesting coating the fiberboard with a waterproof deck paint, provided the thin-set adheres to it and doesn’t impact the fiberboard. I’m also seeing that there’s a product that treats substrates called “MBP Multi-Surface Bonding Primer.” Well, I’m entirely new at all this and feeling quite overwhelmed (HELP!) … so I’m very much hoping you can give me some good insight as soon as possible … which I will GREATLY appreciate!

Reply

Jason

Laying some 12×24 tiles over ditra. What size notch do you suggest? Ditra set says 1/2 x 1/2 notch which seems huge to me. Do I still fill the ditra and notch floor and also butter the tiles also? Thanks!

Reply

Erich Riesenberg

Bostik Ditra-Set is apparently sold through Lumber Liquidators.

A few other places near where I live, and I am in a midsized midwest city, so perhaps it is more widely distributed now.

Reply

Josh

Hey Roger,

I am finally planning on doing the ditra and tile job in my bathroom this weekend. I have been doing some more research and luckily found this information about the unmodified Thinsets. However, unfortunately the Lowes and HD’s around me do not carry any of these that you have mentioned, except the Custom Masterblend :(. (However, Lowe’s had some “Tec Uncoupling Membrane Mortar” which I read is Ditra approved)

So I started reading more, it looks like often you choose to use modified thinset on top of the Ditra for laying the tile. So I would like your thoughts on a couple of things:

1. I am not certain how the Ditra warranty would even be useful for me on a DIY job… I can imagine any faults would be pointed back to me for not hiring a professional. Not to mention I don’t really understand what issues would be covered by the Ditra warranty. For instance, if I followed the directions exactly and my tile cracks or somehow lots of the tile doesnt adhere correctly do they cover things like this? … All this to say the Ditra warranty may not really be of concern for me.

2. I would consider using modified on top. I have VersaBond modified mortar that I am planning to use between the plywood subfloor and Ditra. Would this same modified mortar be a good choice to use between the tile and Ditra?

3. If I use a modified mortar between the tile and Ditra, could I fill the Ditra waffle and lay the tile at the same time and just give that 24-72 hours to harden before applying the grout? I remember reading that you will fill the Ditra waffles the day before you do the tile. Doesnt walking on the already filled waffles mess with the mortar you let set all night?

4. I was considering using the Kerdi Band for the seams at least around the bathtub area. The seams between Ditra there and up to the Drywall around the tub. But I was reading in other forums that the only purpose for using Ditra + Kerdi band is for complete waterproofing.. if you dont make the area 100% waterproof then all you are doing is moving where the water will find its way through. And if you do make it waterproof then there should be a drain for the water to go. Apparently the thought is there should never be enough water splashing out of the tub that a good tile/grout job can’t dry before it would cause damage below. Do you/would you use Kerdi Band in a residential bathroom floor tile install?

Thanks again for your time,

-Joshua

Reply

Sean

Hello,
I just gutted our bathroom and finished everything up . Out Ditra down used modified below and Unmodified above. For the shower backerboards I used redgaurd then based on the same logic as Ditra I used UNMODIFIED for my wall tiles(porcylin)! Everything looks great ..It’s been 10 hours since I’ve finished…Am I going to have a failure and the tiles are gonna fall off?
Thanks

Reply

Roger

Hi Sean,

Nope, you’re fine. Unmodified thinset bonds the tile just fine to redgard as well.

Reply

Sean

You put me at ease, thanks for the reply!

Reply

Greg

Why can’t I use modified thinset for Kurdi Schluter products? I do realize they recommend unmodified thinset but would it really matter? Is it just a question of drying time?

Also what is your Reco for the following interfaces:
1) cement boards and Kurdi membrane (the paper like material) . Note: I don’t see many others doing this but couldn’t you use the membrane on top of cement boards to ensure water doesn’t get through instead of the detra?

2) cement boards and the Kurdi Detra

3) Hardibacker and Kurdi membrane

4) cement boards (or hardi) and tile

5) does the type or size of tile ever dictate whether to use modified or unmodified motar, even if the layer underneath is it Kurdi product?

Reply

Roger

Hi Greg,

Because that’s what schluter requires to maintain the warranty. Yes, it is an curing time issue.

1. I’m unsure where you are talking about here? A shower wall, a floor? The kerdi is used for waterproofing in shower walls, the ditra is an underlayment membrane for floors.

With all your other questions: If the kerdi or ditra is over cement or a cement-based product (cement board) non-modified is used, if it is used over wood substrates modified is used. Non-modified is always used between kerdi or ditra and tile. The size and type of tile makes no difference.

Reply

Francois

Hi roger…. the tile shop where i bought my tiles sold me also the thinset for my project…. unmodified for ditra heat tb and modified for my shower walls … im stuck with redipoxy for the pan (tileredi)!!! I havent seen those in your lists !!! Ever experienced them ???

Reply

Roger

Hi Francois,

I have no experience at all with tile shop mortars. I have used the redipoxy on tileredi pans, it’s a pain. :D Work quickly!

Reply

Joe

Hi,

I’m installing a kbrs sower pan for my shower, they recommend a quality modified thinset and installing it on top of subfloor, however, I want to reinforce my subfloor with some backer board; is that a good idea, and what thinset products you recommend for those layers?

Thanks in advance.
Joe

Reply

Roger

Hi Joe,

Backer board will do nothing to reinforce your floor. It has zero structural strength, it is simply a proper substrate for tile as well as being water stable. If you want to reinforce it use regular plywood. Any good modified thinset will work, I like mapei ultraflex 2 and laticrete 253.

Reply

Joe Pleichner

Hi Roger,
Great article! I wish I saw it before starting on my project. I’ve been retired for quite a few years, and finally, got going on a project that my wife has been after me to do for a long time. That is, to tear out a plastic shower unit next to the tub, and install a tiled shower. I had to re-frame the back wall and shorten the wall between the tub and shower area. I used green board, and sealed the areas where I had to use joint compound(I was worried about the joint compound drawing the water out of the thinset). The flooring store recommended Schluter Kerdi membrane. I ended up purchasing the materials from Home Depot. They gave me the Custom Masterblend to use. I’m not experienced troweling this stuff on, but it was terrible. I tried to make it a little wet as Schluter recommended. It was very sandy and hard to work with. I put the membrane on yesterday afternoon. This morning I noticed that the edges of the membrane on the short wall didn’t seem to be sticking and pealed back pretty easy. Is there a way I can reseal the loose edges and check the rest of the 3 walls for adhesion? Or do you think I have to tear it all out, order new material, and start over again? :(
Thanks so much for your help.

Reply

Roger

Hi Joe,

You can use a good modified thinset to rebond those edges. Scrape off all the customblend crap. You may find, if you peel it back, that the customblend bonded VERY poorly to the kerdi, if that’s the case then it’s likely the case on all the walls. And if that is the case you can probably just peel it all off and reuse it with a good modified thinset.

Reply

Joe Pleichner

Thanks so much for responding and for your suggestions. I’ll give it another day or 2 before I start pulling up a little more on the loose edges. Some areas of the thinset are still a little darker. If I’m lucky, the majority will hold. If not, I’ll take it off as you suggested, clean up the walls a little, then use the modified stuff to reset the fabric. Any recommendations on a good modified thinset?

Reply

Roger

Since you have a home depot close versabond is actually a very good modified thinset.

Reply

Joe Pleichner

Hi Roger,
I did what you suggested and all turned out well. I’m well on my way with the tiling, leaving expansion gaps at the wall and floor intersections. Should I grout as well as caulk those edges or should I only use caulk there?
Thanks!

Reply

Todd Zeigher

My tile store gave me Proma Pro Flex Select modified thinset and told me to use it under all the Schluter stuff and then gave me the Proma Pro Bond un-modified thinset for over the Schluter. I’m struggling to understand why he did this. I put the Kerdi shower floor pan over plywood, and the membrane on the walls over Hardi-backer with the un-modified, ignoring his reco. Was I wrong? Why would he give me modified?

Also I have the honeycomb heated floor mats to install, should I still use the un-modified?

The walls are getting 4×12 ceramic and the floor is getting 12×12 marble, stl un-modified, right?

Reply

Roger

Hi Todd,

You want modified thinset between ditra (or kerdi) and wood, unmodified between ditra (or kerdi) and concrete or cement board. Your shower floor should be fine, though. Although it should have been modified, unmodified normally is not an issue beneath the shower pans.

If you are going over wood you need to use modified. Yes, unmodified between tile and schluter.

Reply

Ben DeJong

I am about to set some 3″ hex tiles (Bianco Carrara Marble) over Schluter Ditra and the only product on your “best” list I could find was Kerabond. Just as I was about to mix the product, I noticed the directions state “not use for moisture-sensitive stone (green marble, some limestone and
granite), agglomerate tiles, cultured marble or resin-backed tiles.”
Would the White Carrara be okay? It does absorb a lot of moisture so I’m not sure if I will be in trouble here? What is the deal?

Reply

Roger

Hi Ben,

You’ll be fine. Most of the stuff it lists is moisture sensitive and will curl (warp) when exposed unevenly to moisture, bianco carrara is not one of those.

Reply

Francois

Hi… im installing a tile-redi shower base on a contrete basement floor .. any recommendation on thinset to use ?? I heard nightmare story about thoose and is seem to be a one shot deal with the drainpipe glueing almost instantly !! Thanks a lot for your website !!

Reply

Roger

Hi Francois,

I prefer mapei ultraflex 2 for that type of installation. And it is a one-shot deal, don’t miss. :D

Reply

Francois

I also read on a forum that some guy filled the ridges under with mortar the base then to flip it in the mortar bed…. seem like a good idea to make sure it completly sit in martar!!! What it your opinion on that ???

Reply

Francois

My other concern is that i have to reposition my drain by braking a trentch in concrete and patch it after…. do i have to wait 28days before intalling the pan ???

Reply

Roger

No you do not.

Reply

Francois

Is 24 hours enough curing before proflex 2 ing my tileredi pan ???

Reply

Francois

Here is phe size of fresh concrete

Reply

Roger

Yes.

Reply

Roger

My opinion is that he can do whatever he wants. :D Definitely doesn’t hurt anything, but it may make more of a mess than it’s worth.

Reply

Ben

I can’t find a premium white unmodified thinset anywhere around here and need a white thinset to place 12×12″ light marble tiles on the floor over Kerdi membrane. Is it ok to use VersaBond Polymer-modified thinset on the floor with the marble tile over kerdi membrane? Also, box recommends 1/8″ grout, but thinking 1/16″ might look better. Thoughts? Also do you ever use a tiling level system like Perfect Level Master T- Lock or QUP lash or just use standard spacers? My floor is super level with concrete board over the subfloor.

Reply

Roger

Hi Ben,

Yes, you can use versabond for that. 1/16″ would look better. I use the MLT system often, it works very well. However, what you are referring to are lippage syste used to flatten the tile, not space them. I would NOT use the lash system unless you are using a minimum 1/2″ trowel. The feet on that system are insanely curved.

Reply

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