Level a Bathroom Wall Ready For Tiles

[RichT222]

Hi All,

I'm renovating a bathroom and putting in a corner shower.

I pulled the old tiles off and it's left the backing plaster in a bit of a mess. The wall where the shower will go is also not very straight. Laying a straight edge across shows it bends by about 15mm horizontally.

What's the best way of leveling this out so it's level with the rest of the wall?

I don't think I can chip out all of the remaining plaster, as it's applied onto concrete blocks and doesn't come off very easily at all. But I could probably take the overall level down by about 10mm.

Following some advice on another forum, I think I'll be using sand and cement render. So my plan is to chip out as much of the plaster as possible in the shower area (to the left of that vertical channel revealing the concrete blocks that you see in the pic), then put a batten in the corner which is level with the remaining wall which is to the right of that vertical channel. Then sand and cement render between the wall and corner batten to bring the whole thing level.

Does this sound like a good plan or overkill or is there a better way to do things?

Please see the attached pics to get a better idea of what's going on.

Cheers, Rich

View media item 27463 View media item 27465 View media item 27464 View media item 27466

 

[Richard C]

The problem with using standard sand/cement render as a base or to level out is the amount of time it will take to go off (up to 4 weeks) before you can tile over it. For holes & leveling, use either a rapid setting render or cement based tile adhesive which you can tile over the next day.

To level up the walls & provide a tile base in the shower area, I would use 12.5mm waterproof tile backer boards & tile straight onto those, job done. To marry into the rest of the wall you can either board out the entire wall to the same level using Moisture Resistant plaster board & tile straight onto that; for areas you need to plaster, it must be primed first. Or, for untilled areas not completely stripped back, fill out with a plaster base coat to the surrounding face & then get the lot skimmed. Base coat Gypsum plasters are not suitable for tiling onto & finishing plaster is generally not as a tile base as it reduces permissible tile weight to 20 kg/m (including adhesive) which will limit the size/weight of tiles you can lay.

Edit;
just notice the studwork on one of your pics, is that across the entire wall? It may be best/easier to remove the lot & re-board the stud.

 

[RichT222]

Thanks for your reply!

Ah, right. I didn't realise that sand and cement render had to be left that long before tiling.

The tile backer boards look good though, if not a bit expensive (I'm assuming you're talking about the Marmox boards). I had only looked at AquaPanel which, from looking at the fixing instructions, seem to require fixing onto battens that create a minimum distance of about an inch from the wall or something (can't remember exactly). The problem is, as you can see in one of the pics, the door frame is right up against the wall. So I can't build the wall out too much or it will end up right at the hinges.

But the Marmox Tile Backer Boards can be screwed right up against the plaster, so should be alright.

It is studs all the way across the wall. Between the studs are concrete blocks, which I'm guessing were put in to help support the weight of a dormer roof extension above. There's an RSJ beneath the stud wall.

I don't think I can get the plaster off without damaging the concrete blocks. It's all pretty solid! So would have to build the remaining wall out a bit so it's flush with the tile backer board.

I suppose I could fix the MR board to the wall's studs using slightly longer screws to take account of the backing plaster depth? (seems to be about 15mm).

It would be nice to just skim straight onto the rest of the wall though, as it's straight and in good condition. Maybe I can attempt to just remove enough of the base plaster in the shower corner to drop a tile backing board in there, and skim the rest of the wall up to it so it's flush. hmm.

Question: Assuming the backing board is level with the rest of the wall (ie, a completely flat wall) and the tiles are applied directly to the backing board, how should the plaster meet the edge of the tiles? Would I just skim up against the tile edging strip?

 

[Richard C]

Marmox are good but I mostly use Aquapanel; it’s equally as good unless you’re building a wet room & is considerably cheaper. Kanuf specify battens for Aquapanel & say it can’t be dot & dabbed but I & many others frequently do exactly that. Dot & dab the panels to the wall in the usual way but make sure know exactly where the adhesive dots are; one way of doing this is to drill small pilot holes at equal intervals through the panel & put the adhesive other those. Once the panel is fixed & the adhesive has gone off (next day), mechanical fix the panels to the wall with suitable length frame screws. The screws must pass through the panel & into the wall where the adhesive dots are or the panels will crack when you tighten the fixings.

Question: Assuming the backing board is level with the rest of the wall (ie, a completely flat wall) and the tiles are applied directly to the backing board, how should the plaster meet the edge of the tiles? Would I just skim up against the tile edging strip?

For part tiled/plastered walls, what I do is ensure the tile backer board extends beyond the shower enclosure/wet area, butt the MR plasterboard (or plaster) up to this ensuring (one way or another) it’s flush & without any appreciable step. I then mark where the tile lines are, reinforce any joins & skim the areas of the walls not being tiled, feathering the skim just inside the tile line; the tile edges cover the plaster & your left with a neat finish ready to be painted; after its dried out of course.

You must apply a couple of 1:1 coats of PVA over the bit of Aquapanel that’s gong to be plastered & just inside the tile line where the plaster is going or you’ll have problems with the plaster sticking to the Aquapanel & you must prime MR plasterboard with Bond It" before plastering as it contains water repellents which, again, will affect plaster adhesion.

 

[plstering]

tile backer board d&d with some fixings in it to help out mite get the walls looking flatish then just sort it out with the tile addy

 

[RichT222]

I've now removed the plaster from the shower area.

I've attached an plan view picture (click to enlarge). The area where I've removed the old backing plaster is where the shower will be (it's about 70cm from the left corner to the start of the base plaster which is still on the wall shown in yellow).

View media item 27625
If I was to install an aquapanel so it sits parallel with the rest of the wall, I would then have to build the wall out by about 1.5 - 2cm to get the whole thing flush, and then another 2mm - 4mm for the skim. Trouble is, I can't do that due to the door frame.

I've decided I'm not going to remove the plaster off the rest of the wall. It took me about 6 hours just to do the small section where the shower will be. It really doesn't come off easily at all!

I'm thinking the easiest thing to do would be to float in some sand and cement, as indicated in the attached pic. If I have to wait 4 weeks for the render to be ready for tiles, then so be it. It's not really a problem. Or should I just use rapid set (is this "rapid set" you talk of tile adhesive, or something else?)

My only concern is: over at the left of the wall (the corner) the depth of whatever I put on will be next to nothing, but over to the right, where it meets the existing plaster, it will be about 1cm - so cracking due to different drying times could be a problem? The wall also has some indents in some places where the concrete block has broken away slightly (after taking off the plaster), which could also contribute to cracking, due to slightly different depths of render? Maybe I should float it first flush to the face of the concrete blocks, to get rid of these slight depressions, scratch it, and then do a final float to bring it level with the plaster on the remaining wall (to the right) ?

Sorry for all the questions! I just don't want to put all the effort in only for it to need ripping out in a couple of years time.

 

[RichT222]

Okay, I've done some more research.

Seems Bal QuickSet Render is what I'll be using. That, or Bal RapidSet Adhesive.

Unless anyone can give me a reason otherwise.