Hardiebacker - can I bed on mortar over floorboards?

[ChrisK]

Hi,

Am about to take on my first tiling job and am throwing myself in the deep end with a load of natural stone (marble and granite).

It's kitchen and bathroom on a first floor, so wooden subfloor. I'll screw down the existing boards and plywood of course, but have bought 6mm Hardibacker to go over it too. Need to fix that tomorrow. I was going to screw it down with Screwfix's 25mm Turbo screws but I know you need to put some mortar or 'thinset' between the Hardibacker and the wooden subfloor. Can I use a weak mortar for this (5ish to 1?), or do I need to use tile cement? If so, can I just use some cheapie stuff, or should I use the Keraquick+Latex I've got for on top? The tile sizes are a 50x50x12mm marble mosaic in the bathroom and then 305x305x10ish mm granite in the kitchen.

Thanks,
Chris

 

[Ian]

Good morning Chris, are you in the UK? Some or your terminology suggests the US, I just want to make sure I give you the correct info.


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[ChrisK]

Morning Brian, yes I'm in the UK, I've just been reading stuff online and in the Hardibacker instructions which I think might even be Australian... Chris

 

[Gazzer]

ok You should use a good quality Single part flexible adhesive and Hardibacker screws. Mortar is a no no. Dont cut corners as it could prove expensive later down the line.

 

[peteablard]

Please don't take this the wrong way but are you capable of doing this job? What tiling experience do you have? As mentioned above if you do this wrong it will be a very expensive mistake

 

[Thepropertytea]

Everyone has to start somewhere, but I echo peteablard comments above. Walk before you can run, try tiling a splash back, your own bathroom , kitchen above a Worktop, not top expensive stone tiles, do you have the right gear to cut them properly etc etc....... Your only as good as your last job!!! Make it a good one

 

[Ajax123]

Will 25mm screws be long enough....... No smutty comments please

 

[White Room]

Thats what I use for 6mm hardie glued and screwed....

 

[Ajax123]

Thats what I use for 6mm hardie glued and screwed....

Ok. I would have gone for thirty five mm..... No real science as to why..... But that's what I would use. i.e. 6mm hardi plus say 5mm adhesive bed and twenty five mm floor boards.... Mind you guess modern floor boards are not 25mm

 

[CJ]

Buy Stainless steel screws........hardibacker screws are crap, unless you pre-drill & counter sink the holes first.

Oh, and they are chuffing expensive (Hardi screws I mean)

 

[stusgsx]

Thats what I use for 6mm hardie glued and screwed....

Same as me. Ever since I hit that pipe.....!

 

[ChrisK]

Thanks to all, yes, I'm taking on quite a bit but am researching as well as I can and trying to buy decent materials that give me a fighting chance, this keraquick is supposed to be pretty good.

Couple more quick questions:
- Do I let the adhesive dry under the Hardibacker before screwing through it, or should I do that while it's still wet?

- Anyone got a screwfix/toolstation link for some tape for the joints in the Hardibacker. The instructions say it needs to be "high-strength alkali-resistant glass fiber tape"?

- Also, am going to tile a short way above the countertops in bathroom and maybe some of the kitchen, again in the heavy natural stone tiles. In bathroom this is just regular plasterboarded walls and kitchen regular plastered brick. I know there are lots of rules about walls bearing tile weight, etcetera, but I'm guessing you can ignore the restrictions it's just one or two rows supported by a worktop underneath. Am I right?

Thanks to everyone, this seems like a very friendly bunch, not like the wolves on diynot...