NO NO NO NO NO!!!!

No mastic in the shower-- EVER.

No mastic with travertine, or ANY stone-- EVER.

No mastic on floors, and ESPECIALLY SHOWER floors-- EVER.

Gosh, some people have differing ways to lay tile and it makes me nervous!

Which is why I spend as much time on line as I do. In all actuality, there ARE many different methods which are acceptable for many of the things we do. Ask a question over at John Bridge's, and you'll see what I mean. However, the widespread use of mastic is not one of them. It DOES have its uses, but they're very specific and limited, and NONE of those uses include wet areas, floor tile, or natural stone.

If that's what your installers are intending, I'd get rid of them now, before they do something that's NOT so noticeable, and shortens the life of your tile just the same. These guys are shoemakers.

Bill, your reply is a little vague. Can you clarify for me regarding mastic in a shower?

Let me translate Bill's posting :)

Ques: What do you say to mastic?

Ans:
Dutch  nr nee
German  nein
Greek  αÏιθ ÏÏι
Hebrew  ××
Hindi  नहà¥à¤
Japanese - ããã
Korean  ìëì¤
Indonesian  tidak
Polish  nie
Portuguese  não
Russian  неÑ
Swedish  nej
Thai  à¹à¸¡à¹à¹à¸à¹ à¹à¸¡à¹à¸­à¸¢à¸²à¸
Turkish  hayır
Ukrainian Â Ð½ÐµÐ¼Ð°Ñ Ð½Ñ
Vietnamese  không khá»ng

Yeah-- what he said!

The plan is to use a concrete bed for the master shower floor. Under that is the liner.

What is under the liner? If it is going flat on the floor that is wrong. The liner must have a slope under it so that any water that gets through the mud bed to the liner (yes, water will go through the tile and grout) will still get to the drain.

Oh, and the reason for no mastic in the shower - or any wet area - is that water can re-emulsify the mastic. The reason why you don't use mastic with stone is because mastic can actually stain the stone.

Wow, thanks for the clarification of NO mastic, I was unsure until I saw it in Greek!

So is thinset and mastic the same thing?

I am in nursing by trade and I know most all about that! But not on tile 101. Thank goodness for professtionals her on GW that do that for a living!

So is thinset and mastic the same thing?

NO! Real thinset comes in a bag in powder form that you mix with water. It is cement based and cures by chemical reaction. Mastic comes pre-mixed in a bucket. Sometimes the mastic makers try to trick you by calling their product "pre-mixed thinset", but it is NOT real thinset. It is mastic with some sand added. Mastic sets up by drying, and if it comes in contact with water can "un set". Just remember bucket = mastic = bad for showers, other wet areas and under large format or stone tiles.

So is thinset and mastic the same thing?

Technically speaking, by strict definition, yes-- mastic is a form of thinset-- that being an adhesive that's applied in a thin bed to set tile into. However, thinset has come to mean any portland cement based mortar made specifically for the installation of thin bed tile after mixing either with water or a liquid latex additive, while mastic is usually referred to as organic adhesive, or "premixed thinset". I saw a new one the other day at Home Depot-- on the side of the bucket they're calling their mastic "premixed thinset mortar". I could see how they got away with calling it thinset, because as I just said, technically speaking, it is. But mortar? I'm surprised no one's challenged them legally about it.