Replacing old tiles with half tile/paint

[jtag]

I will be getting the keys for my 1907 terraced house in a couple of weeks and my first job will be re-fitting the bathroom, which appears to have been untouched since the 60s! I've reading posts on this site for a while now in preparation for the work, it's been a very helpful experience, but I was wondering if I could clarify a couple of things.

There is currently floor to ceiling tiling that I'm planning to remove and replace with a half-tiled, half-painted surface, except around the showerbath, which will be fully tiled. I believe the bathroom has solid brick walls, of which two are external and two internal. I'm not sure what the surface will be like behind the current tiles (I'm trying to get as much of the materials ready before starting).

Seeing as I've not done any form of plastering before, I was thinking it would be worth installing plasterboard rather attempting to skim the existing wall to provide a surface for the painting (using MR board, with tanking around the shower).

Would I be right in saying that I would have to batten the external walls rather than dot & dabbing the PB? If so, would this be an opportunity to add some insulation to the walls?

Many thanks ,

Andy

 

[Richard C]

I wouldn’t buy any materials until you’ve at least remover the tiles & can see what your left with. You can use MR board in dry areas & tile directly onto that. If you want to ½ tile MR board, the bit that’s being plastered must be primed first; mark the tile line & plaster down to this, wasting the plaster into the area just below the line & tile afterwards. I would not advise you just fix PB & then tape & fill; it’ll most likely look awful & just relying on paint in such a damp environment is asking for problems. Plaster the ½ tiled areas even if you have to buy someone in; a decent plasterer will do the whole bathroom in a day at most including the ceiling & that’ll cost between £150 -£180 + materials. For wet areas I would use a waterproof tile backer board, it’s much better than MR PB & will cost about the same once you factor in the cost of tanking the PB.

If you have solid brick external walls then you need to include a moisture barrier. If you just whack the boards up, you will have all sorts of problems with cold spots, condensation & mould. One way is to fit a vapour barrier, batten, insulate & board but one of the specialist insulation boards such as Thermaline Plus is often a better bet;
http://www.british-gypsum.com/produ...es/gyproc_thermal/gyproc_thermaline_plus.aspx
it has insulation, integral damp membrane & surface lining board all in one. Internal walls don’t need to be battened, you can fix either backer board or plasterboard with additional mechanical fixings & tile directly onto that.

Use only quality trade adhesive & grout products of the correct type for your tiles & tile base, the cheap DIY stuff is generally crap. Special consideration is needed when tiling suspended floors if you want it to last. Lots of info in the Tiling Forum Sticky & Forum archive read up if you haven’t done so already & come back if you need more.

 

[jtag]

Thanks for you detailed response Richard!

I wouldn’t buy any materials until you’ve at least remover the tiles & can see what your left with. You can use MR board in dry areas & tile directly onto that. If you want to ½ tile MR board, the bit that’s being plastered must be primed first; mark the tile line & plaster down to this, wasting the plaster into the area just below the line & tile afterwards. I would not advise you just fix PB & then tape & fill; it’ll most likely look awful & just relying on paint in such a damp environment is asking for problems. Plaster the ½ tiled areas even if you have to buy someone in; a decent plasterer will do the whole bathroom in a day at most including the ceiling & that’ll cost between £150 -£180 + materials. For wet areas I would use a waterproof tile backer board, it’s much better than MR PB & will cost about the same once you factor in the cost of tanking the PB.

I'll hold off buying any materials until I'm in then. I will look at getting some plasterer quotes, it wasn't so much the cost that was putting my off, more the 'I made this' factor of doing it all myself!

If you have solid brick external walls then you need to include a moisture barrier. If you just whack the boards up, you will have all sorts of problems with cold spots, condensation & mould. One way is to fit a vapour barrier, batten, insulate & board

So the vapour barrier (polythene sheet?) goes against the wall, then battens with insulation (rock wool?) between and boards on top?

but one of the specialist insulation boards such as Thermaline Plus is often a better bet;
http://www.british-gypsum.com/produ...es/gyproc_thermal/gyproc_thermaline_plus.aspx
it has insulation, integral damp membrane & surface lining board all in one.

I had noticed the Thermaline Plus but it doesn't mention being moisture-resistant; is it suitable for use in bathrooms?

Internal walls don’t need to be battened, you can fix either backer board or plasterboard with additional mechanical fixings & tile directly onto that.

Use only quality trade adhesive & grout products of the correct type for your tiles & tile base, the cheap DIY stuff is generally crap. Special consideration is needed when tiling suspended floors if you want it to last. Lots of info in the Tiling Forum Sticky & Forum archive read up if you haven’t done so already & come back if you need more.

My plan for the floor was to pull up the floorboards, replace with 25mm WBP ply (sealed on underside and edges with SBR) and tile using BAL Rapidset Flexible adhesive and superflex grout.

 

[Richard C]

So the vapour barrier (polythene sheet?) goes against the wall, then battens with insulation (rock wool?) between and boards on top?

If you go down the batten route, I would advise a proprietary wall membrane (can be expensive) rather than polythene sheeting; I think you would be far better off using either Themaline or Marmox.

I had noticed the Thermaline Plus but it doesn't mention being moisture-resistant; is it suitable for use in bathrooms?

No it’s not MR unfortunately; as long as you’re not using it in a wet room or wet area & will be plastering any exposed board it should be OK. If you want to go the whole hog you could use Marmox insulation board; http://www.marmox.co.uk/dry-lining-insulation
Unlike some, this can be plastered after priming with plain old PVA but I don’t know how the cost compares with Thermaline.

My plan for the floor was to pull up the floorboards, replace with 25mm WBP ply (sealed on underside and edges with SBR) and tile using BAL Rapidset Flexible adhesive and superflex grout.

That’s maximum spec board thickness; you can usually get away with either 18mm or 22mm but it depends on floor joist size/pitch/span but if in any doubt go for the thicker board. Nowt wrong with your choice of addy/grout either; only mix up enough addy that you can use in around 30 minutes though, it does what it says “Rapiset”. I prefer it as I can crack on & grout same day but if your inexperienced, then Single Part Flexible might suit you better as it has a much longer pot life; grout after 16 hours min.

 

[jtag]

Many thanks fit your helpful advice Richard, an update on this:

I'm now in the house and have removed all the tiles. In a three places the plaster (about 20mm thick) has come away from the wall completely: around the old shower (now removed), the other side of a leaky gutter (now fixed) and around a crack in the brickwork (the surveyor has said there should be no further movement). The rest of the plaster seems in reasonable condition (the skim coat came away with the tiles though).

Will it be worth re-plastering these sections or stripping off all the old plaster?

Cheers, Andy

 

[Richard C]

If the old plaster is in sound condition then no point in pulling it off but if you use conventional render to repair, you will have to wait 4 weeks for it to dry out (possibly 6 at 20mm thick). If time is an issue, you can use powder cement addy which you can tile over next day or a quickset render. However the size/weight of your new tiles will dictate what you do next; what size/type are they to be? Plaster will only accept a max weight of 20 kg/sqm & that includes up to 4 kg/sqm for the addy/grout.

 

[jtag]

The tiles are quite heavy, 23.5kg/sqm so I think I'll definitely have to use plasterboard/backer boards. Can I put batons on top of the existing plaster?

 

[Richard C]

Which walls are you refering to here, are they the solid external walls or internal walls?

 

[jtag]

It's a bit of a mix!

• One internal wall has all the plaster intact - this one will be 100% painted
• One internal wall has almost all the plaster removed (i.e. bare brick) - to be half/full tiled
• One external wall has most of the plaster removed - to be half/full tiled
• Last external wall has about half of the plaster intact - to be half tiled

All the plaster that has been removed was damaged, the remaining plaster seems in good condition. The brickwork is all dry behind, one area of the brick appears to need repointing where the crack was.

There is also now the added complication of a chimney in the back of the (now removed) airing cupboard that I hadn't noticed before! The plaster on this is cracked but otherwise seems solid.

 

[Richard C]

Where plaster is still there, you will obviously need to get the wall level either by removing the rest of it or packing out. You can dot & dab PB & backer boards directly to the internal walls as long as you use additional mechanical fixings to support the boards & those tiles. Do not rely on the adhesive as the PB will only have the bond strength of the original plaster; backer boards should be mechanically fixed anyway.

For the external walls, please refer to my previous posts regarding a moisture barrier/insulation; the battens must be fixed through the plaster into the brickwork not just to the plaster.

 

[jtag]

Should I put any insulation/membrane/vapour control behind the Aquapanel used around the shower (one of the walls is external)?

Should I treat the (now blocked-off) chimney as an internal or external wall? It's build onto an external wall.

 

[Richard C]

Should I put any insulation/membrane/vapour control behind the Aquapanel used around the shower (one of the walls is external)?

You only need it on the external walls, internal walls you can fix direct.

Should I treat the (now blocked-off) chimney as an internal or external wall? It's build onto an external wall.

Old chimneys should not be blocked off completely, they must be ventilated to avoid condensation forming on the inside leading to damp. They should have a vent fitted at the bottom & a rain cap to the top; otherwise treat it as an internal wall.

 

[jtag]

Thanks Richard, sorry to keep bombarding you with questions, but I'm keen to get it right!

The original bathroom has a high Victorian-style ceiling, which has since had a wooden framework erected below to support a lower ceiling. I am planning to use this framework to mount vapourshield boards and cover with rock-wool insulation. Will I need to insulate the ~12in of exposed wall above the insulated wall boards?

Also, I would like to erect a stud-wall to block off the chimney at an angle, resulting in a void between part of the external wall and the internal boards. Should I place insulation on the external walls or on the back of the internal boards?