# What type of thinset for Porcelain tile?



## BlueBSH

I am tileing a basement bathroom concrete (no cracks, fiber reinforced slab) floor. First time doing this and not sure what type of thinset to use. The tile is a glazed Porcelain floor tile. (12x12 and 6x6 sizes). I've read a few articles online, but no one seems to agree on what to use, modified or unmodified... or an inbetween one...

What would you guys suggest? Also, what is the best trowl for this tile? 1/2, 1/4?

Also is a 1/4" grout spacing good for this? it seems to look the best from my test layouts I've layed down to try out patterns..

Thanks!


----------



## DannyT

i think most tile guys would use modified but either one would work. on porcelain i would burn the thinset onto the back of the tile to make sure you get good adhesion. i used 

unmodified for my 22x22 porcelain tile because that was what was recommended in my situation (large porcelain tile over ditra). the modified needs air to dry, the unmodified doesn't. 

the more uniform the tile is in size from piece to piece the smaller your grout joints can be. if the tile vary 1/16 at the most from piece to piece you would want 3 times that or 3/16 

grout joints. depending on how flat your floor is determines what size notch you need. i think 3/8 works for most up to 12 inches but i'm sure if i am incorrect on anything someone will 

correct me.


----------



## JazMan

Just to clarify Danny's answer; You need to use a modified thinset with porcelain. The only time you can use unmodified is when the manufacturer of an associated system advises to use something else such as with Ditra and Kerdi installations. So unless you're going over such a system, you have no choice.



> I've read a few articles online, but no one seems to agree on what to use, modified or unmodified.


I'd be interested to hear who and why anyone would have any doubts.

I also recommend a base trowel of 1/4x3/8x1/4 for 12" standard tiles. 

Jaz


----------



## BlueBSH

Everything I've read online says to seal the tile before grouting, but this is "glazed porcelain tile". Do I still have to do a seal coat? or will grout just come right off this since it is glazed, not porus?


----------



## JazMan

BlueBSH said:


> Everything I've read online says to seal the tile before grouting, but this is "glazed porcelain tile". Do I still have to do a seal coat? or will grout just come right off this since it is glazed, not porus?


You've been reading at the wrong places.

Jaz


----------



## bob432

I have a similar issue. First, let me say I have a new appreciation for all you tile-laying pros out there. This is my first attempt as a retiree doing DIY around our vacation home, and what a mess. Broken tiles everywhere--tile cutter would break about every other tile. Anyway. I laid Ditra with modified thinset that I mixed, and it worked fine over a wood floor. BUT, I was running out of time and purchased some ready-mixed thinset from Home Depot and used that to lay porcelain tiles over top of Ditra---THEN, I read all the online review horrors how this stuff will never dry or take weeks to dry. So, I left the heat on at the condo, and vowed to return this weekend to grout, or maybe I should wait even another week--OR remove the tile and star over??

Thanks, for any suggestions or even a pat on my back, and say, "don't worry, Bob, it will all work out."

And JazzMan, I see you live in Troy. I live in Rochester Hills...condo is at Houghton Lake.


----------



## JazMan

Hi neighbor Bob,

Well, I'm not gonna pat you on the back, but it might work out. I guess it depends on many factors that I don't know. Like the type and size of this room, how much trouble it would be to start over in 5 years as apposed to now, the cost of the materials involved. 

If you decide to remove the tiles you're gonna remove the Ditra too. Those squares in Ditra are gonna be filled with mastic and covered with tiles it thinks it's still in the bucket, It'll take some time to dry. What size trowel did you use?

Jaz


----------



## bob432

JazMan said:


> Hi neighbor Bob,
> 
> Well, I'm not gonna pat you on the back, but it might work out. I guess it depends on many factors that I don't know. Like the type and size of this room, how much trouble it would be to start over in 5 years as apposed to now, the cost of the materials involved.
> 
> If you decide to remove the tiles you're gonna remove the Ditra too. Those squares in Ditra are gonna be filled with mastic and covered with tiles it thinks it's still in the bucket, It'll take some time to dry. What size trowel did you use?
> 
> Jaz


 Jaz,

I used a 1/4 x 1/4 x 1/4 as recommended by a Lowes' salesman that has used the product before. That said I also spread thinset on the back of each tile to fill the waffle patterns for better adhesion. It's a 4x5 tile space at the entrance door. It's been 4 days since I put the tile down, and they seem fine. No movement, seem hard as a rock. I have also been walking on them. I plan on grouting tomorrow, then won't be back until next week. My main concern is whether the thinset is dry enough to grout. I suspect, the thinset could take months to cure properly.

Thanks, Bob


----------



## JazMan

Bob,

Just for the sake of accuracy and clarification for others, that "pre-mixed thinset" you bought is NOT thinset at all. By industry definition thinset has to be made from Portland cement. What you have is organic mastic with a little silica added. If it gets wet, it'll re-emulsify and you'll have a mess. But, it's a small space, so........?

If it's as solid as you think, I'd go ahead and grout it. You'll get an indication of how it works out by next spring. 

Jaz


----------



## lazzlazz

JazMan said:


> Just to clarify Danny's answer; You need to use a modified thinset with porcelain. The only time you can use unmodified is when the manufacturer of an associated system advises to use something else such as with Ditra and Kerdi installations. So unless you're going over such a system, you have no choice.
> Jaz


Just to be sure I understand: If I use Ditra, I should use unmodified thin set, regardless of what the tile manufacturer recommends?

I'm probably going to use porcelain tiles in a bathroom.
Why do manufacturers recommend modified? One tile shop said it's because it's a little more flexible - is that true? Is it ok to use modified with Ditra because it also will flex a little? 

The tile shop said Ditra has a lot of failures, even when installed by professionals. (They've been around for a while & are a small family-owned shop.) That doesn't seem to be the opinion here - or am I misreading?

Is there a chance of more failure when not following the tile manufacturer's specifications about thinset when using Ditra? Or not really? Does a bigger tile (e.g., 1 foot x 2 foot) have a higher risk of failure?


----------



## JazMan

Hi Lazz,



Lazz said:


> Just to be sure I understand: If I use Ditra, I should use unmodified thin set, regardless of what the tile manufacturer recommends?


Yes, that's right. Schluter recommends using unmodified with ceramic, porcelain and natural stone tiles. Read more from Schluter site; 

QUESTION Can ceramic tile, including porcelain tile, be set on DITRA
with unmodified thin-set mortar?

ANSWER
YES. In fact, we recommend it. Here’s why:
Portland cement-based unmodified thin-set mortars are dependent on the presence of moisture for hydration in order to gain strength. Since DITRA is impervious, it does not deprive the mortar of its moisture. This allows the cement to properly hydrate, resulting in a strong, dense bond coat. In fact, after the mortar has reached final set (usually within 24 hours), unmodified thin-set mortars achieve higher strengths when cured in continually moist conditions.

QUESTION
Can ceramic tile, including porcelain tile, be set on DITRA with latex-modified thin-set mortar?

ANSWER
We DON’T recommend it. Here’s why:
Latex-modified mortars must air dry for the polymers to coalesce and form a hard film in order to gain strength. When sandwiched between two impervious materials such as DITRA and ceramic tile, including porcelain tile, drying takes place very slowly through the open joints in the tile covering. [According to the TCA Handbook for Ceramic Tile Installation, this drying period can fluctuate from 14 days to over 60 days, depending on the geographic location, the climatic conditions, and whether the installation is interior or exterior]. Therefore, extended cure times would be required before grouting if using modified thin-set mortars between DITRA and ceramic tile, including porcelain tile. If extended cure times were not observed, the results could be unpredictable. This is even more important to consider in exterior applications that are exposed to rain as there is the additional concern of latex leaching.



Lazz said:


> Why do manufacturers recommend modified?


Because they don't know you're gonna be using Ditra or Kerdi. 



Lazz said:


> The tile shop said Ditra has a lot of failures, even when installed by professionals.


Nonsense! They don't offer Ditra and so their answer. Ditra has been around since 1987 with about a gazzilion sq. ft. installed. It's used all over the world, thousand of times a day. I don't know of a way it could cause a failure, even if the scrim backing delaminated. (You'd know it before installing though). If there are any failures you can bet it's installer error, I don't know of any. 



Lazz said:


> Is there a chance of more failure when not following the tile manufacturer's specifications about thinset when using Ditra? Or not really? Does a bigger tile (e.g., 1 foot x 2 foot) have a higher risk of failure?


No. Ditra can save your installation down the road by its uncoupling function., to name just one. Use a premium unmodified mortar, stay away from those cheapo ones at the orange and blue vest big box store. What brands of unmodified are available to you? 

Large tiles are always a challenge. Main thing is to start with a very flat floor. Is this a large floor, wood or slab? Where is it located, you didn't list your location. 

Jaz


----------



## RWolff

I installed white porcellain 12" tile in my house a number of years ago, but it was over 2 layers of 3/4" CDX topped with a 1/2" cement board all screwed down well. I used the Mapei thinset and Mapei sanded grout, pretty sure the thinset was latex modified can't find a left over bag of it right now I thought I had.
You will want to follow the directions exactly even though it might not make a lot of sense- mixing several minutes with a drill/mixer, letting it sit for like 5 minutes then mixing for 2 more.
Best use a good 3/8" drill and a jiffy mixer and have a spare just in case, the stuff gets real thick and it's a bit of a challenge for a drill.
I'm very happy with the products I used and there has been no cracks, loosening or failures, not even with heavy dogs playing or rolling heavy sculptures over it on a handtruck.

One last thought- get a tile cutter like I did, one with a diamond blade cause porcellain is so hard you really can't score/break or use regular ceramic score and break tools, at least mine didn't work, so I bought what looks like a mini table saw with about a 5" blade, for wet cutting tile and brick, I think it was about $65 at Menards, a cheap piece of junk but since I only needed a one time thing I bought it for this, it lasted longer than I needed to cut tile for 3 rooms and a hallway, and the included blade lasted that long and will still cut too.

Use hearing protection- cutting the tile is ear shatteringly loud, and eye protection, do it outdoors is highy recommended!



> Broken tiles everywhere--tile cutter would break about every other tile.


If you were breaking every other tile with that tile cutter, why didnt you stop and examine WHY the cutter was not working right? This reminds me of guys at work around machines that start making bearing burning out squeeling noise or malfunctioning, instead of turning it off and getting me, they keep using it till it seizes up or BREAKS! odd/excessive noise, vibration or results not expected are a warning flag, it means STOP! look, examine, find out why something has changed, correct that and then continue.

Breaking every other tile is a red flag that something is not right, either the cutter, the tile or your technique, if you had stopped it would have saved you frustration and a lot of money.
I tiled 3 rooms and a hallway in my house, I don't remember breaking any tile. If you used porcellain tile and tried a score and snap ceramic tile cutter, there's your problem right there!


----------



## RWolff

BlueBSH said:


> Everything I've read online says to seal the tile before grouting, but this is "glazed porcelain tile". Do I still have to do a seal coat? or will grout just come right off this since it is glazed, not porus?


I never read a thing that said seal tile before grouting, I laid my porcellain tile down according to the directions on the Mapei thinset and grouted according to the Mapei grout directions. Porcellain is vitrified, it's so hard you can't believe it, and I used grade 5 commercial porcellain- I don't think anything will penetrait vitrified porcellain, and in fact the grout sealers say to NOT get it on the tile and if you do wipe it off or it leaves white streaks.

Maybe cheap low fire red clay tile such as found around pools and patios needs to be sealed first, red clay is still porous.


----------



## lazzlazz

JazMan said:


> Hi Lazz,
> 
> No. Ditra can save your installation down the road by its uncoupling function., to name just one. Use a premium unmodified mortar, stay away from those cheapo ones at the orange and blue vest big box store. What brands of unmodified are available to you?
> 
> Large tiles are always a challenge. Main thing is to start with a very flat floor. Is this a large floor, wood or slab? Where is it located, you didn't list your location.
> 
> Jaz


Thanks for the information. The tile store said at one time, they sold Ditra, but stopped after failures.

It's a bathroom so not large floor - L-shaped, about 45 sq ft. 2nd floor so OSB subfloor. As I understand, I can put the Ditra right over the subfloor (as long as there aren't any voids; there weren't in the closet); I don't need a layer of plywood (& don't want extra height). This is a 14 year old house & subfloor is in good condition I think (haven't ripped up the carpeting yet, but it was fine in a large closet off the bathroom). 
Location is Seattle.

For thinset, I'll probably us Mapei unless advised otherwise.

I haven't picked the tile yet but I like the look of 1 foot by 2 foot tiles. Of course, those were pretty pricey.

What is meant above by "i would burn the thinset onto the back of the tile". Is that the same as backbuttering?

I have a few other questions but don't want to hijack this thread so am going to start a new one at http://www.diychatroom.com/f5/few-q...ra-layout-tile-kerdi-band-179423/#post1178122.


----------

