Loose Floor tiles :( New Floor

[On one]

A bit of confusion going on here. ......you can't cut a cement based 'Hardiebacker' type board with craft knife.
You can cut an insulated 'cement coated polyurethane 'Wedi','Marmox' type board with craft knife

 

[hmtiling]

I think the board that was put down was a generic hardiebacker board and it was supplied by the builders merchant. All I remember is that you cut it the same way as plasterboard with a Stanley knife. The builder is happy to pay for the works but I just want to be sure, this time it's done right.

Thanks

Cut with a Stanley knife sounds like coated xps, which topps say on their website can go direct to joist. It cannot and will fail. You need to find out exactly what thus stuff is

 

[hmtiling]

I wonder if it was 6mm Knauff Aquapanel, that has a shiny top side and cuts with a knife.

Apparently this board is direct to joists

 

[Boggs]

Oh yeah,
Direct to joists and cuts with a Stanley knife, not sounding good is it...

 

[Waluigi]

I originally thought it was a shiny XPS but the OP said it was a heavy board which adds even more confusion into it.

 

[J Sid]

it's all guess work 😵

 

[macten]

Is NMP shiny now? Never used to be.

 

[bolts]

No NMP isn't shiny, must be something else.

 

[On one]

My thinking was that NMP was shin(ier) that Hardiebacker which has a matt finish.

 

[Southside691]

I think you guys might be right, looking at pics on the web it did look like NMP.

So if the NMP wasn't primed beforehand, would this be the reason for them becoming loose? The builder says it's not down to movement as he screwed the board down really well. Really strange that it's happened in 2 bathrooms on different levels. What would be your advice before the tiles are put down? primer and same brand adhesive or would you suggest something else?