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.
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.
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:
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 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: This is considered Mapei’s premium unmodified thinset. It works very well for any Schluter product
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.
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: 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.*
*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:
Sturdi-Set: Tec’s premium unmodified. A good unmodified thinset for nearly anything requiring one.
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.
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.
Thanks for sharing this valuable information.
An outstanding share! I’ve just forwarded this onto a co-worker who has been conducting a little homework on this. And he actually bought me breakfast simply because I found it for him… lol. So let me reword this…. Thanks for the meal!! But yeah, thanks for spending some time to talk about this matter here on your web site.
I couldnít resist commenting. Perfectly written!
I will be installing 6 x 24 porcelain over JM Go Board in a shower and I assume from your comments that you would recommend an unmodified thin set – like Kerabond – is this correct? Is the unmodified thinset the preferred mortar for these two materials? Thanks for your reply. Dave
Hi Dave,
No. Go Board does not call for unmodified. Schluter products are the only ones that require unmodified. You CAN use an unmodified, but you would be better off with a modified thinset for that.
Hi Roger. Think I may have just completely destroyed a project and hoping I don’t have to rip it all out. I installed a Schluter-Kerdi shower kit with curbs on the floor, waterproofing membrane on the wall over hardibacker and the sloped tray and I used Mapei Thinset Floor Tile Mortar as it appeared to be unmodified and their most basic product but on your list of products, this was not listed. Please let me know if this was ok. It says it exceeds ANSI A118.1 bond strength with water which is what I used.
Hi John,
That is fine. That list is almost two years old and products are being changed and added all the time. Your shower is fine.
You got me through my previous job a few years back, being a redo from slab up of shower. Arched niche, floating bench, and other ‘highlights’. Another home, another delima. A 100 sq ft tile over slab I’d like to redo floor tile over tile. Need the thickness at 2 doorways.
Mapei eco Prim Grip? I would only do if recommended and after belt sanding and cleaning old tile to the hilt.
But, recommended? Crack resistance? Ditra first after Prim Grip? No easy access to Laticrete where I live now, so Kerabond?
Hi LaNell,
The order of stuff is correct (you actually DO NOT NEED to sand down the tile if using prim-grip, just clean it really well. Prim-grip is a fabulous product). Over prim-grip you want a modified thinset to bond ditra, not unmodified. If you have availability to mapei the ultraflex 2 is perfect. Over the ditra, under the tile, yes, kerabond is correct.
I should add these tiles are porcelain
Hi David,
The mapei uncoupling will work just fine. As far as the modified, ultraflex 2 is really good. Nearly any mapei modified will work well, though. If you are using the kerdi-band you do not need any of the liquid anywhere.
Thank you so much, appreciated! One more quick question- if I’m using wonderboard with kerdi membrane- do I also need to put 4 mil plastic sheeting directly over the studs sandwiching the board with 4mil and kerdi membrane? Or wonderboard directly to studs with kerdi on top should do the trick?
Wonderboard directly to the studs with kerdi over it – no plastic.
Same answer. (I answer them in the order received, I don’t see this one until I answer the last).
Hey Roger-
I’m installing a curbless shower with a schluter tray. Bathroom subfloor is plywood using ditra and then the walls I’m using wonderboard covered with kerdi membrane. The tiles are large format. What do u recommend I use as the unmodified thinset for the large tiles over the ditra, kerdi membrane, shower tray? Mapei uncoupling medium and thinset mortar is easily available at Lowe’s but I can source whatever u want. Any recs on the modified I need to use between the plywood and ditra? And – do I need to apply a liquid membrane if I’m using the kerdi membrane plus the kerdi strips at the seams with thinset? Thanks for all your help
Hi David,
The uncoupling mortar will work just fine with that tile over both the kerdi and the ditra. Any modified mortar should also be sufficient, since you have a lowes close the ultrflex 2 works really well. No, you do not need the liquid membrane as well.
So my wife ended up leveling our kitchen floor down to the Plywood which is great. Next her and the neighbor who has done a diy bathroom decided to lay down the ditra with the Unmodified thinset. The said they read both of the bags I got and thought that was the correct thinset. Called ditra and they stated it may or may not work. But they stated I need to or course use Unmodified to place the tile on the ditra. It’s only been there for maybe 20 hr at this point. Should we just pull it off and start over or leave it and hope it gets a good bond?
Hi Finley,
I’m a little late to this, but even after 20 hours it would have been a chore to redo it. The unmodified WILL bond to the plywood. The issue will be the normal expansion and contraction of the plywood breaking the crystals in the mix that allow that bond. Modified has polymers which allow the mix to retain water, which causes the crystals to be thicker and stronger. That is simply a long way to say the same thing, it may or may not work.
It is up to you whether to take that chance or not. If it does fail the ditra will become unbonded to the plywood and you will end up with a floating tile floor (not bonded to the substrate, but the tile will be bonded to the ditra (locked into it, more accurately).
Should you move forward with it as-is, be on the lookout for cracking grout lines – that will be the first indication that the ditra has become unbonded.
Can I use the Laticrete 317 to set a 3/4″ thick granite slab over Kerdi membrane? It’s a 14″ x 44″ piece that I’m using as a shower bench top. I will be using a 1/2″ square trowel on account of the size of the slab, but the 317 doesn’t give coverage for 1/2″ square trowels. I’m therefore wondering if Laticrete doesn’t consider 317 to be appropriate for large format tile.
Hi Elmo,
Large format tile mortar exists to prevent excessive shrinking while curing. If you have two tiles next to each other and one has more mortar beneath it, that one will shrink more, causing the tiles to no longer be even once cured. It is not required for one, single large slab.
Yes, you can use 317 for your granite slab over kerdi.
I put down porcelain tile in a shower floor using thin set mortor in a bucket that did not have polymers in it by mistake (Recommended by Home Depot employee). I have the concrete floor, then red guard over that, then the thin set mortor, then the tile on top. I submerged the floor under water for 2 weeks hoping it would loosen up, but it has not. It is still hard and won’t budge at all. This is a new house construction and won’t be in it for several months. If I let this dry for several months, would it be ok to leave it in there?
Hi Laurie,
Provided your shower floor was waterproof, it’ll remain waterproof. I have NO idea whether or not the tiles will remain bonded. Flip a coin. Sorry.
Have done a few tile projects with Hardibacker, but am now venturing into Ditra first time…also to complicate things, I’m using 24 x 24 porcelain. Do the mortars that are called “large format/tile” mortars really make a difference with a tile like this? I guess the idea is it holds a thicker trowel notch better?
Does the Schluter all set work for large format tiles?
Thanks in advance…this site has been a great resource.
Hi Kevin,
Those mortars have more sand in them so they do not shrink as much. With the amount of mortar needed under large format tile, regular thinset may shrink excessively causing the installation to have lippage even if it was completely flat when set. All Set does work, but the lft mortars work better.
Pot life of Schluter All Set is very poor in my experience. I usually get 75-90 minutes max and that’s at highest level of water for tile setting. They advertise 2-4 hours which is completely false. Open to suggestions but may try Kerabond T for tile setting over Ditra.
Why would use anything else it voids the warranty?
Your warranty is not void if you use an unmodified thinset – no matter the brand.
That is incorrect. To receive the lifetime warranty you have to use their thinset
Aahh, ‘lifetime’ warranty. Sorry, missed that part. Yes, you are correct.
Hi Al,
Kerabond T works well. Humidity, temperature water temperature all also play a big part in the pot life, and not equally with different products. All set seems to be sensitive to air temperature and humidity in my experience. I’m not a fan either.
I was slightly misguided/misunderstood after speaking to someone at Lowe’s when asking about modified vs unmodified thin set to install tile. I originally planned to use ditra and the instructions said to use unmodfied over slab and modified over subfloor to adhere to the membrane. The Lowe’s rep said that’s because modified thin set won’t properly adhere to the slab. Now here’s the issue: I decided to forgoe the ditra membrane. Using the info the I hit from Lowe’s, I used unmodified thinset direct on slab to lay my large format tiles (12×20). Now I’m reading up on it and it appears the bond issue is NOT because of the slab but because of the time for curing under ditra on why to use unmodified.
Everything I’m reading makes it sound like my results will be disastrous and my tile is going to crack. Is this the case? It’s a small 5×5 bathroom…. do I really need to rip it up?
Hi Sue,
No, it will not be a disaster and no you do not need to rip it up. Provided you installed it correctly with proper coverage the unmodified over the slab will be just fine for your tile. Really.
My local Lowes carries something from MAPEI called “Uncoupling Membrane 50-lb Gray Powder Thinset/Medium Bed Mortar”. It appears to be unmodified thinset based on the labeling. Any idea where this might fit in your ranking above? I can’t easily find Laticrete or the “Keraxxx” products nearby.
Thanks
Hi Mark,
That mapei product is a good one. It’s right up there with the keraset and kerabond.
Thanks!
Roger,
I used your advice a few years ago on a master bath remodel, and used DitraSet. It worked great of course. Now however I am doing another bathroom and the tile shop I use doesn’t carry it any more.
But…
Apparently Schluter now makes their own mortar! After talking with the owner of the shop, I went with a couple sacks of Schluter SET. He suggested either that or their ALL-SET, but that was twice the cost.
Anyway, have you used the new Schluter mortars? Do you like them?
Hi Andy,
I have used them. They are great mortars, but I’m not a great fan. They are just too sandy for my taste. Not what I’m used to more than anything else. That’s the only issue I have with them, and that’s everything to do with me being a stubborn old bastard rather than a negative for the mortars.
Thanks Roger! I’ll use it since it’s what I have. And being that it’s a Schluter product and I’m doing it all Schluter-style, I’ll assume it is good stuff. Hopefully the dog doesn’t blow up.
Your site has been such a go to resource throughout my first attempt at renovating a bathroom… Thank you! I decided to use the Schluter systems, and have been using the Laticrete 317 (as you advised!) but have run out and still have the floors to do. My local tile shops were out of the 317 and have suggested a product from Texrite called “Floor Mix” (it does meet the standards, but like some of the others on this list, I’m afraid it may not be worth using!). Any thoughts/experience with this product? One person went so far to say this is the same 317 in a different package but I thought I’d ask another expert!
Why not use Schluter’s All-Set? That’s the best stuff on the market today imo
Hi Dusty,
The problem is that a LOT of people do not have that available anywhere near them – including myself. If I want it I have to drive to Denver, I’m not doing that. Availability is normally the biggest factor in choosing an unmodified mortar.
I just order mine off of Amazon if my supplier is out it is a little more expensive but I feel confident in it. But it is tough to fine sometimes for sure.
I checked amazon but at $40+ a bag that didn’t work. Found it online Floorlife just over 20 a bag and since doing multiple rooms ordering 15 bags was cheaper than amazon even for their delivery.
Thank you for the quick response Dusty, but I am having trouble tracking some down near by, and the shipping was about as high as the bag on Amazon :/
Hi Misty,
I’ve never seen nor heard of that, but I will tell you it definitely is not 317 in a different package – that’s BS. A good indicator of the quality of a mortar is the price – find something that is around the same price point of the 317 and you’ll be fine.
Yep! That is what I was afraid of! At only $6 a bag, I thought it couldn’t be right! I found a local flooring store that can order in the 317… I’ll just use the down time to dry fit and cut a million little hex tiles. If you have tips for cutting small mosaics (I’m planning now to use my wet saw) I’m all ears.
I’m guessing this is an old post based on the number of comments. but while I found your #1 pick I also found
Schluter Set White 50 lbs Bag UNMODIFIED Thin-SET MORTAR which was cheaper. Is theirs better? like everyone I don’t have a lot of money and this is a big project for me 350 square feet kitchen/laudry/hall and pantry. porcelain tile also very expensive but going over a concrete slab. Already have the ditra but as it’s a dyi I cant afford time or money for cracking tiles or the product to fail on me. I’ve been waiting years to do this project and want to make sure I’ve got the right materials.Please take a moment to give your suggestion.
Schluter Set White 50 lbs Bag UNMODIFIED Thin-SET MORTAR
Schluter thin set is awesome. I love the ALLSET Because you can use it anywhere.
Hi Terry,
Schluter set is actually the perfect mortar for your application. It is awesome stuff.
I did go with the schluter thinset bought it online at just over 20 a bag. Even with shipping the cost was less than I had planned on. Thanks for the feedback.
Hi! Thanks for the very helpful website. I recently started a kerdi application and used the only unmodified thinset I could find at lowes. I think it was worse then the keraflor you mention. it was just a $8 bag of mapei unmodified thinset. I knew nothing of the premium levels. It was like sticking cardboard to dirt. I knew something was wrong but couldn’t figure out what since the bag of mortar said it met the standard. Nothing in any of the product literature mentions “premium.” I had to get it so thin, saying it would hold the trowel lines was a stretch. I know you would have to see the actual finished product to make any real recommendation but curious what your thoughts are. You mentioned “it’s a last call” so i guess you are not saying “absolutely not tear it all down.” Right? I do a water test tomorrow….
Hi Matthew,
I would check the bond after the thinset cures. You would still be able to peel it off if you tried (you can with any thinset) but you would need to put effort into it, it won’t peel up like a sticker. Your flood test will tell you everything you need to know.
Thanks. I failed the water test so bought some schluter thinset. Was night and day difference. Very sticky, good bonding. I trimmed an edge of the existing wall membrane held by the cheap thinset and it came right off even falling off in sections. Going to hope that was just some poor bonding near the edge and keep going but really wish I had started with some better thinset (seen this website sooner).
Hi Roger,
Several years ago we installed the Ditra in our bathroom then tiled it. We are now updating the tile so we’ve taken all the old tile and Ditra out. The tile and Ditra came out with some hard work and power tools. We had some exposed plywood and some thinset left on the floor. I went to Lowes and the associate sold me the Mapi Kerabond T thinset fill in the pockets of missing thinset from the plywood and to lay the new Ditra to the floor. We levelled out the floor and let it dry for two days, then layed the new Ditra. It has now been drying for a few days. We have been doing a lot of reading and research on what products to use below and on top of the Ditra but we are just confused. Having read that the Kerabond T is unmodified, not modified, have we already set our project up to fail? Also, can you please recommend a thinset to apply on top of the Ditra for use with a porcelain tile.
Thanks for all your help!
Hi Tara,
If you used unmodified over plywood it may fail. I can’t guarantee a failure – it may be just fine. It depends on the amount of expansion and contraction in your floor. Unmodified can not handle very much, it isn’t flexible at all. With ditra over wood it needs modified between the wood and ditra. Between the ditra and tile always requires unmodified.