Which floor Tile Adhesive for hardie backer?

[Neil 28]

Hello everyone a very happy new year to you all!! It’s been a while since I last posted!!


Currently renovating my bathroom and now at the stage of tiling. However I need some advice in sourcing the correct adhesive for the floor. I have removed the old floor boards as they were cracked and warped and installed 18mm wbp ply instead. I have also replaced two joists and supported the floor with extra noggins. The joist centres are 280mm. The floor is sound with no deflection, I used my laser level hooked to a tripod to measure the movement and there was very little only if I jumped.


The plan is to install 6mm hardie backer board to the plywood prior to fixing the tiles. The tiles will be 10mm porcelain and I wish to glue the hardie to the plywood and then screw down to the joists.
My question is which adhesive do I use for gluing the hardie? The products I have narrowed down are:

Ardex X7001
Ardex X7R
Ardex X78

The X7001 is designed specifically for wood based boards and sheets, and after speaking to Ardex technical services they recommend this, but it is very expensive compared to the others. I know mapei keraquick can be used but only if mixed with their latex solution, which brings the price up to X7001.

Can I get away with using the other two products or anything else besides the X7001? Also I will be screwing down the boards anyway, so hence can I just get away with using any flexible adhesive? What would you peeps do?


Thanks in advance for your advice and support.

Neil.

 

[Gazzer]

Hardi state a non flexible adhesive I believe ( dont use it myself) as its only to fill in voids below the hardiboard. The screws hold it down.

 

[Neil 28]

Thanks very much for your reply, i also read that on hardie backers website, and told ardex technical department but he was adament that to achieve a solid bed, definitely use a flexible adhesive. To be honest i am inclined to use any flexible adhesive as you said the screws are going to the hold the boards and the adhesive just fills in the voids.

Funny thing is the ardex tech guy never heard of anyone gluing hardie down prior to tiling, I thought that was it was a common practice in order to achieve a sound floor prior to tiling.

 

[Gazzer]

I heard that boards could be fixed without adhesive and when I was working in Australia , this is how it was done.
I myself prefer to use a single part adhesive and screws if using Hardi.

 

[AliGage]

6mm hardie would still flex if there are any voids. New ply floor with very minimal deflection is great. But for the sake of a little time and addy id be sticking and screwing.
Belt and braces and all that.

 

[charlie1]

6mm hardie would still flex if there are any voids. New ply floor with very minimal deflection is great. But for the sake of a little time and addy id be sticking and screwing.
Belt and braces and all that.

Ill be honest here, I'm not 100% sure exactly what hardie does in terms of minimising deflection. I have been using for a year now with no problems as a replacement for plywood. I use mapei p9 and 25 mm screws to secure.

 

[widler]

To be honest,if the floor is flat I don't know what the addy would do ?
With NMP you glue with a Silicon gun,just shows you to put a few lines on the back,lay it,jump on it and screw it,if there's any voids that bit of glue ain't gonna fill no voids .
I understand the hardie way(if the floor is uneven) but the NMP way seems odd if it's uneven !

Pa I've just laid a floor with NMP using addy and screws not there glue,I couldn't see it working on this floor

 

[Gazzer]

Chipboard/ply floors I use NMP glue if its flat as they say its the adhesive that secures the board. Screws just to clamp it and they reckon no more than 8 per board. I do a lot more though.
If its T&G boards then I use SPF and screws...what ever works for you I say .

 

[widler]

No i agree neale, but, with the glue even on a flat floor ,with not entirely covering the board, won't it cause small voids under the NMP ?
Its quite thick stuff is the glue .
Its just sometimes i think its a conspiracy to buy there gear to make more money, just call me paranoid 🙂

 

[Gazzer]

I know what you mean and I have asked questions of these companies before but without any real answers.

I have seen it said that you can just lay boards with no adhesive.
Hardi say the adhesive is to support the board not secure it.
NMP say the adhesive secures the board not the screws.
NMP say 2 beads of glue and inbetween eajoin of teh boards and it can do X amount of boards !! No it cant , That adhesive doesnt go that far.
And why do they all say you must use our screws ??
You could well be right about the theory but I guess they are doing their job and we have to do ours.