Mortar, Trowel and RedGard

[Jamboaz]

Just when I thought I was ready to roll, I read the directions.

The RedGard states, "Install tile with a Custom polymer-modified mortar (do not use pre-mixed ceramic tile adhesives.)"

I bought the mortar from Lowe's, Mapei Ultracontact Ultra-Premium Full-Contact mortar.

My questions:
1. Is this the wrong mortar to use? I don't see anywhere about polymer modified and such.

2. Is there any problem using a polymer-modified mortar with ceramic tile? For that matter, what is the difference?

3. I'm install 20"x20" tile, what size notched trowel should I use? The bag indicates a very large trowel.

Sorry in advance for the noob ?'s.

Thanks,

Jamboaz

[Jerbo]

Ultracontact would be a great product to use. Keep in mind it uses less water than a normal 50 lb. bag, but it's actually wetter looking. It is also a good medium bed mortar that will work great with your 20x20.

[Jamboaz]

I should clarify these 20x20 tiles will be put on the floor, over concrete slab. Should I still look for another product?

[Jerry Thomas]

Is your tile a porcelain or just regular ceramic?

The trowel size is dependent on the tile's backside. If its flat it may take one size trowel, if its gridded with fairly deep recesses it would take a different trowel. What you are trying to achieve is 100% coverage.

Make sure to key the thinset to the concrete good then comb it in one direction to help eliminate any air pockets. It's also a good idea to key or back butter the tiles too.

I would start with a big trowel like a 3/8 by 1/2 and set a couple then lift them to check the coverage.

Modified thinsets take longer to cure under a big tile like that so don't be too quick too grout it.

[Jerbo]

I should add a bit of info on the "contact" mortars on the market. Usually, 50 lb bags of thin set require roughly 6 qts of water to get proper mix. "Contact" mortars (such as Mapei's Ultracontact, Laticrete's Sure Set, Custom's Complete Contact) require roughly 5 qts of water. In addition, they appear wetter than normal peanut butter consistencies of regular thin set. It sorta defies logic that less water can result in a thinner consistency, but it is the case. In addition, the ridges tend to slump a little when run thru by your trowel. Do not worry, though, because the Ultracontact will actually act as a medium bed (better support) even though it is not as stiff. The beauty of this is that you don't have to back-butter your tiles like you would with normal thin sets. Not having to hold a 20x20 tile upside down and back-butter every one saves you some serious arm muscle fatigue. I agree with Jerry that normal thin sets recommend back-buttering on all tiles 12x12 or larger, but the "contact" mortars eliminate this need. Just make sure to lift the occasional tile to ensure good coverage.

[Jamboaz]

This is cermaic tile, not porcelain. Back buttering would be tough. In hindsight, I wish we had gone with a smaller tile for that and other reasons.

So from what I'm gathering, the mortar bed is actually a bit thicker than if this were smaller tile. With that in mind, I think I have another problem. This tile is supposed to meet up against some existing 12" tile. I'm planning on making a small, 6" wide transition between the two rooms of tile by cutting tile from both sections into small pieces and forming a transition pattern.

Will the 20" tile be higher than the existing 12" tile? If so, what is the best course of action so I don't get a toe stubbing effect every time I go from one room to the other? The rooms are separated by doors, which are generally left open. The transition tile pattern would be in parallel where the doors close.

Thanks,

Jamboaz

[Lazarus]

I never have been much of a fan of just butting one type of tile up to another. I like to make the "transition" with a marble threshold or, at the very least, a wood "T-Mld." Another thought is to cut your tile into a small pattern...triangles or such and fabricate a "break" between the two rooms. How about a strip of matching mosiacs?

You're only limited by your imagination........

[Jamboaz]

My wife had the same idea. We saw a pattern at a neighbor's house we liked and we are going to try something similar.

Thanks,

Jamboaz

[Bud Cline]

Typically a twenty inch tile will certainly be thicker than any twelve inch tile if you are comparing 20" ceramic to 12" ceramic. Stone tiles will be a different story in most cases.

If you intend to abut 20" to 12" you may want to leave out the 12" (thinner tile) until the 20" (thicker tile) is in place then slightly ramp the thinner tile to meet the thicker tile if ramping is an acceptable solution to the thickness variance problem.

I guess I don't understand the backbuttering explanation above. The need to backbutter has little to do with whether or not the adhesive is a "contact adhesive" (whatever that is) and has more to do with the way the back of the tile is manufacturered in conjunction with the plane condition of the substrate.

Twenty inch tiles almost always require backbuttering but of course the trowell also enters into that determination.

[Peter Kodner]

Lazarus, good to see your back form the dead and visiting here Welcome aboard!

[Lazarus]

Thanks.....not quite dead yet~~

I stop by regularly...but just to add something in the tile section. It's not real active so I don't say much unless there's something I can contribute.....

Laz~~

[TFP Admin]

You are more than welcome to liven up the Tile forums anytime you want, Lazarus. Give them a kick start with an exciting new topic. Shake it up with some difficult questions. Let them scratch heads with some interesting and even controversial comments.

T

[Jerbo]

Ah, there's no better feeling than having advice on a product dismissed by a forum moderator who's never used the product.

DIY'er bought a full-contact mortar that is ideal for his job and is easy to install, which I believe all DIY'ers want. Just thought it would be a great idea to let him know. I threw some of the product names out there in case any tile setters wanted to learn about them and see if they might save them some time and increase their profit margin. That's part of what I do for a living. I know tile setters bust their ass for a living, but it can be difficult to keep up with all the changes in technology. Good luck with your job, Jamboaz.

[TFP Admin]

See? Like that. Good one, Jerbo.

[Jamboaz]

I just posted in another thread that I've given up my dyi-er dream of laying 20" tiles on a diagonal and instead am handing it over to the pros.

The person I'm using says they are going to backbutter, so I get to see their technique and hopefully learn a few things.

The only problem we've noted at this point is to Bud's point. The 20" tile against the 12" tile means we will have lipping. We are going to put in a transition combining the two tiles into a pattern of smaller triangles and short, straight pieces. I'm going to point out what I'm after and see what kind of magic they can work.

Thanks again!

Jamboaz