Ditra - google it.

Ditra appears to be a newer product. I'm asking if "floating" the tile floor is a standard construction method?

Around here, "floating" a floor is similar to floating a shower ... wire and cement are used on the floor before installing the tile to create a flat surface.

I've not heard of the term, but your description of the underlayment not being attached to the subfloor is not what you want to do. The underlayment is either thinsetted & screwed (cement board) or thinsetted (Ditra) to the subfloor.

And Ditra's not all that new. I first used it in 2007, and it wasn't new then. It's easier to install and superior technology.

In a basement, ceramic tile could also be laid on top of plywood that is "floated", i.e., not attached to the underlying concrete, on top of XPS sheets, as per BSC-Renovating Your Basement.

(Ditra was invented in 1987.)

This post was edited by worthy on Tue, Sep 2, 14 at 17:53

My apologies for being unclear about the Ditra. I wasn't looking for products per se, but rather what the standard construction technique is for laying a tile floor that doesn't crack with minor seasonal shifting/settling.

Ditra will 'decouple' the floor from the tile. It is a plastic membrane with 'fleece' on the back. The fleece side is affixed to the floor with thinset. The fleece allows for movement of the floor not to affect the tile.

It can be installed over plywood.

Jewel, where are you located? In California, floating a floor is as I described, but maybe "floating" means something different in different parts of the country. Why are you asking? Where did you hear the term? Did you receive a quote with "floating the floor" listed as part of the scope of work? There are a variety of methods to prepare inadequate floors for tile installation, and "floating" is one of those methods.

standard construction technique

The Code I work under--OBC 9.30.6--9.30.6.4--lays out a number of permissible alternatives. The technique I see most often is commonly called a "scratch coat". Tile is set into a mortar bed no less than 32mm thick that is reinforced by 50x50mm wire mesh over felt, poly or asphalt sheathing paper. The underlying wood panelling shall be at least 20 mm thick and the floor supported at no greater than 400 mm intervals. I have found this inadequate--grout cracks eventually appear, especially in high traffic areas such as laundry rooms. So I double the subfloor thickness and add Ditra.

Do you have a specific application in mind?

Thanks, All. I'm just trying to figure out why our new master bath tile floor (reno managed by a GC) already has two cracked tiles and a ton of cracked grout. The previous tile floor had zero problems in 14 years...

The only thing we can figure is that the process/underlayment didn't protect the tile from the slight seasonal shifting this spring. The previous tile was simply laid over drywall (yes!) that had been glued to the plywood sub-floor. Seems substandard to me, but it performed better than whatever the GC used under our new tile.

This post was edited by Jewel654 on Tue, Sep 2, 14 at 21:35

What did your GC use under your new tile? Did he say he floated the floor? Did he use wire to reinforce it? How thick did he float it?

What is the size thickness and material of the old and new tile?

"floating" has too many other meanings relative to flooring to be used to describe decoupling ceramic tile from a wood structure. Historically this was done with a thick mortar bed reinforced with metal mesh that required the floor framing to be lower in the tiled areas. Waterproofing or building paper placed below the "mud" bed provided the decoupling.

Glued drywall underlayment was a cheaper way of doing the same thing using organic adhesive which suggests it was a DIY job. I suspect it survived because the floor did not get very wet.

I can't think of a reason a professional tile setter would risk not using Ditra or a cement backer board (or both) for your floor.