If this is a DIY tile job, 18x18 over concrete is a pretty difficult install.


KT

No it's not. It might be labor intensive, but it's not difficult. Prep the surface, lay out your tile, starting in the center of the room, arrange the tile how you want it, ie. square, diamond or what not, then work off of it. Don't call me when it comes to grouting.

A good set of knee pads is a must.

If your surface is wood, given your climate, you might consider putting down a vapor barrier.

That's exactly what the old vinyl floor is doing.

right, don't know what I was thinking. Between all the concrete and wood, vinyl, linoleum, I lost focus.

Yup it is. For 18x18 the floor must be very level.

OP - Lots of 'interesting' advice in this thread, think about it, and do it right.

Trekkor - scrape the old floor up, check for humps with a straightedge, perhaps a leveling compound... why the Hardiebacker over a concrete floor?

thanks guys, concrete floors

I say depend on what result do you expect. If expecting an ok result, that is it very hard, but if expecting a perfect/beautiful tiles job, it's can be very hard. I know someone who cares every single gaps between tiles, in fact no gap at all. It has to be perfectly leveled everywhere, knocking every tile with a coin after done, and more. To get to that level, the bigger tha tile, the harder it get.

To prevent tile crack, maybe?
I am thinking about hardi board or maybe kerdi ditra
http://www.johnbridge.com/wp-content...itra-deck4.jpg

I was responding to another post regarding the Hardiebacker.

Over concrete, scrape all the old adhesive off. Cover any cracks with an isolation membrane.

I will never use Ditra.


KT

For 18x18 you should have less than 1/16 of surface deflection in 4 ft.
I use Level Quik self leveling underlayment from Custom exclusively.

LevelQuik® RS (Rapid Setting) Self-Leveling Underlayment | Custom Building Products


KT

My appologies. I rushed my reponse and missed read the OP. Hardi backer isnt needed in this application due to concrete floors. I agree scrape up the vinyl check for level. thinset new tiles down.

trekkor,
I was thinking that I will use ditra on my next floor tiles on concrete, but if you don't like it, there must be a reason that you can see. Can you go into a little more detail? And can you recommend some kinds of isolation membrane?