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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Sharon

Hi Roger, I am wondering if your recommendations are up to date? I have compared your recommendations to what’s at the John Bridge site and am finding older comments there (from 2003) about Laticrete. How often do you update your recommendations? I have 12×24 porcelain tile going down over Ditra, and I am a DIY-er. Do not want to redo later! Want to ensure I use the best product I can find. Thanks!

Reply

Roger

Hi Sharon,

I keep it up to date as much as possible. While there is ALWAYS new stuff coming out constantly, the chemical makeup and performance of these thinset remains the same. If it ever does change I change my posts to reflect that, as well as putting the word UPDATE in front of any said changes. Although I act like a jackass I’m fairly efficient at some things (unless you ask my wife…). :D

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Jodie in Texas

Hi there. I’m new to your sight and have a few questions. I’m about to install Kerdi and I know I’m supposed to use unmodified thin set. After I’ve done this, am I supposed to install the tiles with unmodified thin set or modified thin set? And if it’s the unmodified, am I supposed to add anything to it? I’m installing 12×24 tiles subway fashion. Thanks for your input.

Reply

Roger

Hi Jodie,

You need to use unmodified thinset, and no, don’t add anything to it.

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clayton

Roger, Would detra-set work well to install porcelain tile ,12×24 tiles, in my tub/shower area? I have a hardi- backer board substrate installed.
My plan was to “paint” the backer board with Red-Gard waterproof membrane for my water proofing but you say don’t do that? I have not other waterproofing in place. Thanks

Reply

greg

Clayton – I just used ditra set on 12×24 dal tile poreclan and it was great. They stuck to the wall like you wouldnt believe.. infact, I had a heck of a time peeling it off to check for coverage. I use wonderboard with Kerdi over it. Fair warnning – with that size tile you need a 1/2 x 1/2 trowel so you burn through the thinset quick!

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Roger

Hi Clayton,

Ditra set would work fine, but a good modified thinset would work better. Where did I say not to use redgard? I don’t believe I’ve ever stated that. Redgard is a great product for your shower wall waterproofing.

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j

Hello fellow Coloradoan…
You ranked your unmodified thin-sets. Do you have a ranking of modified thin-sets? Thanks

Reply

Roger

Hi J,

Sure! Which hundred would you like me to rank? :D

Modified thinset come in so many different varieties, with so many different aspects and benefits to each that it is nearly impossible to rank them based on one-another. For instance, Mapei ultraflex 3 has a high flexibility aspect, as well as high psi. Versabond has high psi as well as having a finer sand content (creamier workability). Depending on the particular needs of a certain installation I could rank them on flexibility, psi or workability. With the three options mapei would be at the top of flexibility and versabond on the bottom, they would be even on psi, and versabond would be at the top of the workability scale whereas mapei would be quite low on that list.

With unmodifieds they all do the same thing (essentially), they are not manufactured to have specific aspects built-in like flexibility, etc. Modifieds are specifically manufactured for certain things, so impossible to compare them with one another in a general category.

Tell me what you’re doing and I can recommend a modified thinset for that particular application. Sorry, that’s the best I can do. :D

Reply

j

Thanks for the reply.
I am looking for a good quality modified thinset for Ditra over plywood underlayment. I am looking for a good quality product that I can pick up locally in the Denver/Front Range area. 12×24″ tile will be going over the Ditra.

On another note I stapled down (1/4″ narrow crown x 1″ galvanized staples) my 3/8″ ply underlayment. Then I looked in the Ditra installation guide to see they say no staples for the underlayment :bonk: . Do you think this will be a problem? Would i be betterr off ripping up my underlayment and use ring shank nails? I stapled appx every 2″ on the perimeter and 4″ in the field.
Thanks again

Reply

Roger

Hi J,

You should be able to get a hold of mapei ultraflex 2, that would be a good thinset for that. You can leave the staples in, but you should either go over it again with ring shanks or screws.

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Justin

Thanks for the quick reply I appreciate it very much

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Justin

Hey quick common question I’m sure. I am mostly looking for reassurance…I installed 1/2″ Kerdi board in our shower and started tiling with white 4×16 porcelain Subway tile.

I wanted to use a white thinset and could not find any white unmodified so we picked up custom building products Megalite and proceeded to tile the shower. From what I read my only concern is a longer dry time before grouting is this correct and do you have any suggestions as far as how long to wait before grouting.

It’s in a bathroom where the temp is 20 degrees celsius or more at all times

Reply

Roger

Hi Justin,

Yes, longer curing time. I would (honestly) wait about a week before grouting, but don’t be too concerned with it. The megalite works just fine over kerdi-board in real world applications.

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Jim Murray

Hi Roger, would 1/4″ ply give some stiffness to a 3/4″ OSB subfloor 16″-ish O.C.? The Depot sells some advertised as “underlayment” and as a substitute for Luan, is this my best choice? I’d prefer not to use a backerboard since I just need to build up the thickness and I’m using Ditra anyway.

Thanks, jim

Reply

Roger

Hi Jim,

It won’t stiffen it, but it can be used to build up the height if you need to.

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joe

Hey Roger I recently had someone tile my foyer and it was done while I was at work. I came home to them just finishing up and noticed a lot of lippage and almost no tile level. I ripped it up right away and cleaned off the tiles before everything hardened and decided to redo it myself having done my kitchen before. I scraped the floor as much as I could before it hardened but I am left with a thin layer of thin set over the existing concrete that is really sandy. I bought a sander and that seems to be working but I sweep and then sponge it off but it seems there is always fine sand coming off of the the previous thin set. Is this going to be a problem can I seal it somehow? What thin set should I be using? I have a bag of unmodified Tec from Lowes will that be good enough? Thanks, Joe

Reply

Roger

Hi Joe,

The sand isn’t going to hurt anything, it’ll be locked in once you use new thinset over it. The unmodified will work, but it would be better to use a good modified thinset directly to the concrete.

Reply

joe

Thanks for the reply Roger! I swept and wet sponged it off again today and now what’s left seems to be stuck down pretty good. I’m going to see if I can find one of the better modified thin sets you recommend on here and attempt it tomorrow.

Reply

Jeff

building shower with hardi board and kerdi. First mistake ? – used Custom repair floor mortar bed and over taped seams in hardi. I don’t plan to use it beyond that, but realize I have areas where my thinset under kerdi will adhere to Custom – not hardi. Should I grind it off. I plan to seal hardi before thinset application to reduce hardi sucking up water. Tile supplier provided Siena multi plus pro m200 for thin set. It modified – not good for kerdi. However, Ardex x5 will work for kerdi, how do I determine if the siena m200 product has similar characteristics of ardex x5.

Thanks – appreciate your insight

Reply

Roger

Hi Jeff,

Do not seal your hardi. Any type of sealer is a bond breaker and you WILL NOT get a good bond. Use the x5 for everything in your shower, take the sienna back, you don’t need it for anything.

Reply

Jeff

Thanks – truly! Ok to keep “custom” over seems an cover with x5?

Reply

Roger

Yes.

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Bram

Hi,
Really enjoying your site! I’m putting radiant heat into my basement (concrete slab), using Ditra Heat and tile on top. Because it’s so cold down there I’m using cork underlayment to provide some insulation and make the radiant wires more efficient. I’ve read all the instructions for Unmodified Thinset for everything except plywood subfloors and Ditra, but what about bonding the ditra heat to the cork underlayment? It’s technically a wood, so use modified thinset for that and then unmodified for the tiles? The schulter website is mute on this substrate….

Thanks for any help!

Reply

Roger

Hi Bram,

You are correct, modified thinset for installation of schluter products over cork.

Reply

Jon

Hello.

Great Site!

My Lowes has a mortar that is not mentioned here. It is Mapei’s uncoupling matt mortar. I’m wondering if you’ve had experience with that, and how it compares to Kerabond.

Thanks,

Jon

Reply

Roger

Hi Jon,

It is good stuff. Comparable to ditra-set or kerabond.

Reply

Slartibartfast

One more thing. I found Tec Full-set Plus at Menards, that’s the best I can do semi-locally and given the price & availability it looks to be what I’ll go with. You said to, “ensure full cure time before the next installation stage.” Tec lists 2 cure times on the bag, 16-24 hour initial cure, full cure in 21 days. Do you mean that I need to wait 21 days to grout?

And to clarify my earlier question about good vs poor mortar, to a novice like me it would seem that if the product meets the ANSI standard, it should work… but I’m a novice… and while I understand there are different recipes, I don’t understand what make one better than the other while they still both meet ANSI specs.

Reply

Roger

The full set is a good mortar. You need only the initial cure time before grouting.

Reply

Slartibartfast

So today was the day to start tiling. I’ve been picking up supplies for weeks, reading, figuring, laying it all out in my handi-dandy CAD program, replacing subflooring, etc. and today I finally started putting the Ditra down. I bought the only dry-set mortar I could find, which happened to be MAPEI Floor Tile Motar (KeraFlor) — with the added bonus that I could mix it with the Polymer addative for use on the bonding layer and then use the stuff for setting the tile as well. Oh… the best layed plans…

Then, while looking for some additional info, I found this page and discovered that MAPEI KeraFlor is the “It’s last call – find something” motar. Ugh. I used 1 bag and put down about 115 sq. ft. of Ditra using this. So, is this stuff OK for bonding?

Next question… I’m in semi-rural America… Lowes & Home Depot are the main places to buy without extensive travel… where do you get your supplies? Any ideas where to look?

Last question. I can special order Kerabond from Lowes, it’ll take 2 weeks to get here and the price is almost 4x the cost of the KeraFlor. Can you elaborate on why the KeraFlor is so poor of a choice? I’m not trying to convince myself — well, maybe a little — but I’m interested in what makes a good/poor motar.

Also, while at Lowes this evening trying to find SOMETHING other than KeraFlor, the flooring sales guy told me to just use modified thinset over the Ditra — said that that’s what their installers use and there’s no problems! When I mentioned that Schluter says it’s a definate no-go his response was that Lowes warraties all the work anyway so it wasn’t a big deal. :roll:

Thanks again for the help.

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Slartibartfast

Must have missed the paragraph at the end about where find the stuff… sorry. Feel free to skip that answer. Sometimes I’m and idiot. :)

Reply

Roger

The keraflor will work, it just isn’t the best on the list. Given where you have to purchase from that is your best option. The ratio of the mix is what determines the ‘better’ thinsets, but it’s purely relative. They all work. You can use modified over schluter, but you’ll lose your warranty.

Reply

Carla

Bought Ditraset for installing membrane over Kerdi tray & Curb, as well as for tiling over these and Kerdi Board on the walls. Can Ditraset be used over Kerdi board for tiling? The bag says to use Kerdiset for tiling on Kerdi. I can’t even find this product on Bostik’s web site.

Thanks for your time!

Reply

Roger

Hi Carla,

Yes, it’s perfect for that.

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Deb

First, let me say I have really enjoyed visiting your site. I have found a lot of great information.

I decided at the last minute that I would use the Schluter Uncoupling Membrane mat for my floor instead of the hardibacker I originally purchased. After doing a bit of research I now know that I need to use a modified thinset for adhering the mat to the wood sub-floor and use an unmodified thinset to set the tile. Unfortunately, however, I can only find Mapei Kerabond and Custom Uncoupling Mat Mortar (which I did purchase without thinking about the color) at my local stores and only in gray. The tile I have selected is 6×24 beige (has swirls of brown throughout). The grout is Mapei Navajo Brown. Do you think it will be okay to use the gray uncoupling mortar I already purchased or should I keep searching until I can find white?

Thank you

Reply

Roger

Hi Deb,

They gray will be fine. With porcelain and ceramics, unless they are pure white, gray is normally always fine. It’s the natural stones that run into problems with beiges and grays.

Reply

Jared

Roger,

I love your site – thank you!

1) I’m installing a tub surround over new drywall and ditra heat floor. My tile store recommended Tec – Full Flex modified thinset for ditra to plywood, tile to dita, kerdi to drywall, and tile to kerdi. I questioned them and they reassured me that this is correct. Very reputable store. Should I return the thinset and get something different?
2) Ditra Heat – Is this a good membrane to use? It hasn’t been out too long.

Thanks!

Reply

Roger

Hi Jared,

1. The ONLY place you should use modified thinset is between ditra and plywood – everything else you’ve mentioned should be installed with unmodified.

2. YES! I will NEVER install in-floor heat again with anything else.

Reply

Jared

Thank you for the response. I double checked with the tile store this AM and they cleared up the mis-information from the first sales person – confirmed by you just now. Next step – I’m ordering your books and getting this job done! Thank you!

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