Quick bathroom question

[Dammit]

I've divided the bathroom into teo rooms using studwork, the smaller room will be an ensuite for the bedroom.

Where the shower will go is in a corner, two of the walls are aquapanel that I will tile directly onto, the third wall is original to the flat, and is cinder block with bonding and finishing plaster on top.

The original wall is also a long way away from being flat- so I'd like to go over it with bonding plaster to get it flat enough to use large tiles on.

Should I PVA over the current plaster before slapping the bonding on?

Should I tank the wall after bonding it but before tiling?

 

[paul78]

you would pva before but dont use bonding on the wall as its not suitable for tiling!

Couldnt you level it with rapid set tile addy????

or hack the bonding off and baton the wall out and use aquapanel again then no need for the tanking which will save money also.

 

[Richard C]

You cannot tile over Bonding plaster (or any base plaster), it’s completely unsuitable as a tile base; in fact plastering a wall you propose to tile over is rather a bad idea full stop. You can tile over finish plaster but it has a weight restriction which can be a problem if you’re proposing large format tiles. Let’s have a lot more detail info on what you’re proposing including tile size & take it from there.

Here is the standard boring stuff:
There are many things to catch you out with tiling, particularly if you intend tiling a suspended timber floor. I would advise you read the Tiling Sticky & Forum Archive posts before doing any more work or buying materials, it could prevent you making disastrous & potentially expensive mistakes. It’s important to use only quality trade tilling materials of the correct type for your tiles & tile base; cheapo own brand & DIY stuff is mostly crap.

 

[Dammit]

Ok, from the top:

- The flat is in a 1930's Art Deco block
- Poured concrete frame
- External walls are brick
- Internal walls are cinderblock
- Pretty much no wall is square to another wall
- Pretty much no wall is flat, many are "pregnant"

The finishing coat plaster is so tough that you cannot get a masonry nail into it- you have to drill it with an SDS to get through it.

Back to the situation at hand- I have constructed my stud walls, and the shower cubicle has these on two sides, both of which will be aquapanel then tile.

The third wall needs to be squared up, which is where I am now.

I've not yet bought the tiles but would like to use large ones, preferably a natural stone variety.

I could rip off the plaster from the wall and then dot and dab aquapanel on it I guess- but that would be days of pain with the SDS drill on chisel, I'd rather render the wall, then tile onto it.

Suggestions please!

 

[xr4x4]

If your talking about the original 'plaster' on the Walls, it's more likey to be sand cement render on a place of that age.

 

[Dammit]

If sand/cement render forms a bullet proof surface that barely dents when hit with a sledge hammer, then yep- sounds like it.

 

[Dammit]

It's flat grey if that helps? Top/facing layer that is, sand coloured for the (very thick) layer that is directly onto the cinder block.

 

[Richard C]

The finishing coat plaster is so tough that you cannot get a masonry nail into it- you have to drill it with an SDS to get through it.

Pretty difficult to say without seeing it but you need to establish exactly what finish you have & how well fixed it is before you can asses if it will support the weight of the tiles you want to use.

I still think it’s most likely to be plaster over render base; finish plaster can be pretty hard but the render underneath is usually relatively soft unless a really strong mix has been used but this would be prone to cracking. The alternative is to mechanically fix tile backer boards over the lot & tile onto that.

The third wall needs to be squared up, which is where I am now.

How far out of square is it? It won’t necessarily notice unless you’re going to tile the floor as well but will obviously affect anything you place against two adjacent walls.

I've not yet bought the tiles but would like to use large ones, preferably a natural stone variety.

You need to establish the size & weight sq/m of the tiles you’re going to use; this will dictate what you do next. You also need to ensure that the backer board joint lines won’t line up with any joint lines in the tiles or you’ll risk it cracking.

I could rip off the plaster from the wall and then dot and dab aquapanel on it I guess- but that would be days of pain with the SDS drill on chisel

You don’t have to remove the old plaster to fix tile backer board, there is no point; fix over the top. Dot & dab method is probably the best way as it will allow you to level up the walls. You cant rely on the adhesive alone; you must also add mechanical fixings to secure the boards after the adhesive has set.

I'd rather render the wall, then tile onto it.

If you use conventional render you will have to wait at least 4 week before you tile. You can use a quickset render but it’s rather more expensive. Have you done any rendering before & are you confident you could get it flat enough for large format tiles?

 

[Dammit]

Ok, I am coming round to the idea of using tile backer board.

When you say "mechanical fixings", could you please expand on that?

I am assuming that you refer to screwing into the wall, but from my limited experience of these things I would think that I would need to use plugs, and have no idea how I'd get these into the wall through the board!

The wall bellies out by around 20mm in the middle, when a straight edge is held against the wall from floor to ceiling- could dot and dab accommodate this variation in surface flatness?

 

[Richard C]

When you say "mechanical fixings", could you please expand on that?
I am assuming that you refer to screwing into the wall, but from my limited experience of these things I would think that I would need to use plugs, and have no idea how I'd get these into the wall through the board!

You don’t use plugs & screws, use these;
http://www.diy.com/diy/jsp/bq/nav.j...2150&fh_location=//catalog01/en_GB/categories<{9372015}/categories<{9372044}/categories<{9372210}/specificationsProductType=wall_plugs/specificationsSpecificProductType=plugs___screws&ecamp=aff-p9-awin-001&ecamp=aff-p9-awin-001

Or these;
http://www.screwfix.com/p/fischer-s...w&cm_mmc=AffiliateWindow-_-DeepLink-_-Na-_-Na
but don’t hammer them in, screw them in.[/quote]

Some board manufacturers have their own proprietary fixings but they do more or less the same thing.

It’s very important that the fixings go through the adhesive or you'll distort & crack the boards when you tighten them up; drilling 3mm tell tale holes help with this. Don’t fix until next day after the adhesive has gone off.

The wall bellies out by around 20mm in the middle, when a straight edge is held against the wall from floor to ceiling- could dot and dab accommodate this variation in surface flatness?

20mm is excessive; if the “bellying” is uniform you could fit a couple of battens top & bottom to fix to & use dot & dab on the central part to level up.

 

[Dammit]

On the opposite wall I have used 2X3" timber to create a studwork frame that stands just in front of (and is attached to) the wall, but obviously creates a flat surface.

I'm going to board this, then tile it.

I don't have the room to do this on the the wall I am discussing here.

Unless I could use 10-20mm battens at the top and bottom of the wall, then bond the board on, thus flattening it?

 

[Dammit]

Also- I still don't understand the fixing bit.

If I need to get a 5mm plug through the board I need to drill a 5mm hole, in which case the 5mm screw head will pull through?

 

[Richard C]

Unless I could use 10-20mm battens at the top and bottom of the wall, then bond the board on, thus flattening it?

That’s what I’m saying but use screws through into the battens not adhesive; use adhesive dabs on the centre section of the wall

Also- I still don't understand the fixing bit.
If I need to get a 5mm plug through the board I need to drill a 5mm hole, in which case the 5mm screw head will pull through?

Both the fixings are “through” (frame type) fixings. If you look at the links you will see that the integral plug has a support under the screw head; you drill your hole, insert both the plug & screw, the plug expands in the wall behind as you tighten, it doesn’t pull the screw head through.

 

[Dammit]

Ah- ok, so the plug goes in flush with the surface of the board rather than into the wall behind the board?

That would explain what has long been a mystery to me!

Battens and glue sounds like a plan, I'll have a crack at that and report back.

 

[Richard C]

Ah- ok, so the plug goes in flush with the surface of the board rather than into the wall behind the board?
That would explain what has long been a mystery to me!

It’s the standard method used to fit double glazing units & is why they are generically called “through frame fixings”; but you can get than in varying lengths for all sorts of uses now.

You might need to countersink the face of the board a little so the screw head & plug sit flush but don’t overdo it.