Hardiebacker onto terracotta hollow tile wall

[Waluigi]

The single only reason I would ever use MR plasterboard in a Bathroom is if I was using TE boards and filling the joints.

For all areas outside of the shower area I would tile directly on to bare standard plasterboard.

Keep in mind that if you do skim MR Board, you’d need to use Thistle bond it. MR board isn’t designed to be skimmed bare. It has a coating.

 

[adibell]

Using the MR plasterboard in the wet areas and tanking, would there be a difficulty tiling onto the surface of them because of the coating? Does a tanking system offer a good adhesion surface, or would I also want to use something like Gripcoat to give a mechanically grippy surface? Would I also potentially see an issue tiling onto the standard plasterboard with the weight of my tiles (20kg/m2)?

I feel like plasterboard is the best option cost-wise, I’m just concerned the bath won’t fit if I add 2x 12.5mm + the dabs at each end of the bath. But I guess I’ll find out when I strip the plaster off later today.

 

[Waluigi]

Get everything stripped out and see what you have.

The depth of a dot and dabbed plasterboard might be governed by how Plumb your wall is either side of the Bath.

As a general rule- tanking doesn’t reduce the weight you can hang off PB but each tanking products is different. You would never usually need to prep the tanking before tiling.

 

[adibell]

But would the surface coating that prevents you from skimming onto MR plasterboard also mean that your tiling adhesion isn’t great?

 

[Waluigi]

..... it’s absolutely fine to tile direct on to MR plasterboard.

 

[adibell]

Cool, fingers crossed for they fit the !

 

[adibell]

Ok so I could just about fit 2x 12.5mm if I squeeze the bath into place, but assuming dot and dabs will add a cm or two onto this, I can’t fit anything 12.5mm in place, unless I only board down to the top edge of the bath. I assume this is a terrible idea and opens up to water ingress significantly.

Would 6mm tile backer boards suffice on the walls to hold tiles, or are these a bit too flexible?

I’m getting a distinct feeling I’m going to have to take out one end wall and build a stud one instead, just for the sake of a couple of cm!

 

[Waluigi]

Lose the Bath in the wall if the rim on the Bath is big enough. Both ends if you want it even.

If you have to dot and dab one end in after the Bath is in then no problem at all. Keep in mind that you should be installing batten/CLS on the underside of the Bath to support it.

 

[Boggs]

How big is your bath?
Some 1700mm baths actually only measure at 1675mm. This might help you a bit

 

[adibell]

Hi so the bath is 1690, but the walls are 1710 apart. So realistically there’s not actually enough room for the bath plus the boards. Have decided I’ll have my first go at buildjng a stud wall as it doesn’t seem too hard, plus I can put in some recesses for shower gels etc anyway. Will simplify the process, I can use MR plasterboard and tank it, plus I won’t have to plaster the hallway wall on the reverse side, which is a bonus.

Any recommendations for tanking systems?

 

[Waluigi]

Only if you say thanks

 

[Boggs]

Tilemaster.

 

[adibell]

Of course sorry! Thank you all for the advice, it’s been really helpful! I’ve took the wall out now, so will be removing the rest of the plaster tomorrow, building the new wall and getting the plasterboard on hopefully!

Thanks again!

 

[Waluigi]

Might be the best way forward. At least you can decide exactly where your new wall is.

 

[Raccus]

provided the Tiles don’t exceed the weight limit of 32kg PSM inc Adhesive and Grout, I’d Dot and Dab Plasterboard onto the wall. There’s no need to add mechanical fixings to plasterboard

A query about your comment..... the thought i have, is if normal plaster finish walls can only hold about 20kg psm, how can a dot and dabbed only boards hold more? For arguments sake, say the dot dabs made contact with 20% of the area of the boards, that implies that the dot/dab adhesive is over 5 times stronger than plaster, as its covering only a fifth of the area but holding more weight. Is my logic correct?