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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othar

wow! thanks for the great info, I’ve been a little lost on different thinsets until now. quick questions-
1- do you use laticrete 317 for everything that touches the kerdi? kerdi to wall. kerdi to any kind of tile.

2- will laticrete 317 stick to drywall mud, primed walls, or painted walls?

thanks, o

Reply

Roger

Hi Othar,

Yes, yes, and…um, yes. :D If your walls are painted it’s always better to rough up the paint a bit with sandpaper to allow a better bond.

Reply

Michael

Hi Roger,
I’m installing a tile kitchen floor using Schluter-Ditra, my options available as far as unmodified thin-set are Mapei Floor & Wall Tile Mortar, and Custom Building Products, Customblend Standard Thin-set Mortar. Kerabond and TEC, Uncoupling Membrane Mortar can be ordered but would take 2-3 weeks before arriving and I’m pressed for time. Would either of the first two choices be acceptable. Thank you so much I enjoy all your useful info.

Reply

Michael

Hi Roger,
I just found TEC Full Set Plus Thin-set Mortar 380 at a local store so I’m guessing from your unmodified thin-set rankings that, that would be my best choice if I do not want to wait for a three week order to arrive.

Reply

Roger

Yes.

Reply

Roger

Hi Michael,

Personally I would wait for the tec, but the mapei floor and wall will work fine.

Reply

Rodney Hamilton

will unmodified thinset (which is called for with a Kerdi shower system) hold my tiles (porcelain or ceramic) to the wall as well as modified thinset

Reply

Roger

Hi Rodney,

Yes it will.

Reply

Rodney Hamilton

to kerdi or not to kerdi it sure looks like a good product for the diyer, but some “old school” installers say it is not that good. Your thoughts on this Elf

Reply

Roger

Hi Rodney,

Move forward or DIE!

Everyone who is not educated in a method does not necessarily feel comfortable with it. I’m an old-school installer. :D

Reply

Andy

Hi Roger,
I am installing a Kerdi system in a shower stall I am adding to my basement. I am using greenboard as a substrate. Before I found your site, I installed the corner strips of the Kerdi using the crappy Custom thinset from Home Depot. I installed the pan using the same. I have not installed the curb yet and I have not applied Kerdi to the floor or walls. I have found Laticrete 317 at a tile store, so I will be using that for the rest. Should I re-do the corners using that? If so, do I just rip the Kerdi down and sand off as much of the Custom stuff as I can? Thanks for any insight.

Reply

Roger

Hi Andy,

I’d just leave it. The kerdi-band junction is where it is bonded to the wall, not where the kerdi overlaps and forms the waterproof seam. It’ll be fine.

Reply

Michael Harkins

can I install ditra on top of dal seal

Reply

Roger

Yes (still). :D

Reply

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