Remove Plaster or Overboard - Solid Walls & Large Format Tiles?

[EViS]

What's the best method for preparing solid walls which have been plastered, ready for tiling with large and heavy stone tiles (e.g. 600x400 marble)?

a) Would you remove the plaster and hope that underneath the walls have been rendered? Otherwise the browning or hardwall would need to come off down to the brickwork/blockwork. or
b) Overboard? In which case would you batten out the walls first, then fix hardiebacker? Or screw hardiebacker directly into the walls?

The second option is going to be more expensive, but will leave you with perfectly flat walls. What's the most common route for you guys?

 

[DHTiling]

You can D&B Marmox boards ( min 12.5mm) and then mechanical fix through the D&B's.. this is good if walls are uneven.. if the walls are flat then you can serrate the walls and then mechanical fix at regular intervals..

 

[Ajax123]

Can you not just dot and dab cement backer board onto the existing and screw through into the structure with mechanical fixings....

 

[Ajax123]

Ahaha...... Dave can type quicker than me it seems

 

[EViS]

You can D&B Marmox boards ( min 12.5mm) and then mechanical fix through the D&B's.. this is good if walls are uneven.. if the walls are flat then you can serrate the walls and then mechanical fix at regular intervals..

Is it merely a preference for using Marmox, or are they in some way superior to the Hardie boards? And as far as fixing goes, would dowel fixings (such as these) be adequate to hold the weight of large heavy tiles?

Can you not just dot and dab cement backer board onto the existing and screw through into the structure with mechanical fixings....

I can, however what is the reason for dot and dabbing (unless the walls aren't flat)? Otherwise you're merely sticking the board to the weak substrate you're trying to get away from? The mechanical fixings will be doing the primary work, no?

 

[DHTiling]

You cannot D&D hardi.. ...

 

[Ajax123]

Based on the recommended shear load of each pin at .15kN each pin will hold 0.015kg.

What weight is your trav??

 

[Ajax123]

You cannot D&B hardi.. ...

Not even if you support it with mechanical so the dot and dab is just to keep it flat and level?? Every day is a school day

 

[EViS]

Not sure of the stone's weight. But 600x400 marble isn't going to be light! I guess that at 20 dowels per board (0.3kg), they wouldn't even hold half a tile :s. If that's the case, and I've just checked the data sheet myself too, what on earth is the use of those dowels/pins?

 

[DHTiling]

The last time i asked Al, Hardi said NO!... but if they have changed that decision , then hopefully someone will say so..

The Hardi 250 can be used on walls but must be fully embedded into adhesive and the hardi 500 is for stud work..

 

[EViS]

Not even if you support it with mechanical so the dot and dab is just to keep it flat and level?? Every day is a school day

I guess that's why you wouldn't use hardiebacker in this scenario .

 

[DHTiling]

Not sure of the stone's weight. But 600x400 marble isn't going to be light! I guess that at 20 dowels per board (0.3kg), they wouldn't even hold half a tile :s. If that's the case, and I've just checked the data sheet myself too, what on earth is the use of those dowels/pins?

You can screw with marmox washers as well.. my preferred fixing method.. and these fixings go deeper than just the base and skim coats.. you plug into the walls structure and if stud wall, then you screw into the studding.. very strong fixings then..

 

[Ajax123]

If you use screws rather than plastic pegs it will increase the shear weight capacity hugely.

 

[EViS]

Sounds like the way forward (i.e. Marmox boards mechanically fixed with washers and screws). Where is the best place to purchase Marmox boards? Do Topps stock them?

As the second alternative, do you guys ever remove plaster from solid walls? Or does this leave the walls too uneven to tile onto?

 

[DHTiling]

PHG Wetrooms , link below.

 

[Ajax123]

Topps........ Toppsssssss! Not my tiling advisors at present........ Had a conversation today with their "technical" expert in one of their shops........ Never heard of uncoupling membrane............WTF (scuse me)

The advice that an "anti crack" mat should be placed within the screed and not stuck to the top was the one that made me most angry!!

Please..... Use someone who knows what they are talking about ........ You could do a lot worse than PHG IMO.......

 

[EViS]

I shall get in touch with PHG. Any national merchants which stock Marmox at reasonable prices and from whom I can collect?

 

[DHTiling]

Postage from PHG is cheap..

 

[Dougs Third Go]

The last time i asked Al, Hardi said NO!... but if they have changed that decision , then hopefully someone will say so..

The Hardi 250 can be used on walls but must be fully embedded into adhesive and the hardi 500 is for stud work..

yet shearing strengths aside Dave, I've always wondered why we dot and dab plasterboard, surely a better fixing method for p/b would be a solid bed?

 

[DHTiling]

Hardi 250 is only 6mm doug and PB would be 12.5mm , so stronger board for support between dabs don't you agree ?

 

[Dougs Third Go]

I know what you mean Dave, but I was thinking more along lines of point bearing a mass weight on a few dabs of dri-wall, surely the strength of a fixture is only as strong as its weakest link so to speak. As I say, it's just summat i've been mulling over lately:smilewinkgrin:

 

[AliGage]

The last time i asked Al, Hardi said NO!... but if they have changed that decision , then hopefully someone will say so..

The Hardi 250 can be used on walls but must be fully embedded into adhesive and the hardi 500 is for stud work..

I always beleived hardie couldn't be dot and dabbed. Job i'm on at the moment i fixed a timber studwork/frame to the block wall and fixed the hardie to this.

 

[ythan]

I'd check the plaster on the wall is well adhered and solid simply by tapping it.

No problem then tiling directly onto the plaster.

As the tiles are vertical the weight of the tiles is transferred down through the tiles. The lateral strength of the plaster and tile adhesive needs to be sufficient to keep the tiles vertical rather than supporting the whole weight of the tiles.

 

[merit]

im looking forward to the replys to the last post

 

[Rookery]

im looking forward to the replys to the last post

Yeah thats a corker.