No experience,so looking for advice.Pics added

[broontroot]

Hi, newby here so go gently



Right......my intention is to fit a new bathroom suite and shower cubicle, so i've been busy removing the old tiles. Some tiles have came off ok, leaving only the tile adhesive, other have pulled off large bits of plaster.

I'm in an ex-local authority house, built probably mid 50's, and has cavity walls(not insulated if that matters).

Where large areas of topcoat? has came off, i'm left with a sort of rough powdery plaster probably 1/2" to 3/4" deep, though no bare brick is visable.
It looks like the odd bit of straw i can see in the plaster.
The max depth of plaster which has came off when removing the wall tiles is probably around 1/4", though in most areas it's only 1/8" or a few millimetres..
The walls were tiled halfway up,and will be again tiled halfway up, so i was going to plaster the section of wall where the tiles go myself, and get a proper plasterer in to do the area above the tiles, which will be seen.

Is it ok to use pva glue to 4 or 5 parts water to sort of seal the bare areas where the top coat has fell off?

I have made sure the remaining plaster is firmly bonded to the brick.

Also is it ok to use one coat plaster to fill the low areas up to the level of the existing plaster, before tiling?
By 'onecoat' plaster i'm meaning the pre-mixed stuff out of a tub.
Obviously it wont be seen,but will need a strong bond.

Also a question regarding the old tile adhesive,........does it get scraped off or sanded off, or is it ok to leave it on, as new tiles will be fitted over the top of it?
Cheers

Edit-
some pics added (hopefully)

 

[Richard C]

What size, weight & type of tiles are you thinking of hanging, this will dictate what you need to do next. Even in good condition, plaster has a maximum weight limit & if your tiles weigh in at more than around 18 kg/sqm you will have to provide a more suitable tile base.

Plastering/re-plastering where you intend to tile is not necessary & is not a good idea, apart from the weight restriction, you will have to wait at least 10 days for it to dry before you can tile. Your better off using a cement powder adhesive, which you may need if intending large format tiles anyway or a quickset render. Forget the pre-mixed one coat crap, it will give you nothing but grief & don’t use base plaster to fill out, it’s not a suitable tile base. For the area above the tiles, mark a line where your tiles will come to & get your plasterer to skim down to it & blend in just below the line; do this before you tile. You will need as flat a tile base as possible particularly with large tiles so remove the old tile adhesive.

When tiling or re-tiling, there are many things that can catch you out. With walls, you need to consider tile weights, prep & materials & suspended timber floors need special consideration. I would advise you read the Tiling Sticky & Forum Archive posts before doing any work or buying materials, it could prevent you making disastrous & potentially expensive mistakes. It’s also 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.

 

[huddsspread]

What size, weight & type of tiles are you thinking of hanging, this will dictate what you need to do next. Even in good condition, plaster has a maximum weight limit & if your tiles weigh in at more than around 18 kg/sqm you will have to provide a more suitable tile base.

Plastering/re-plastering where you intend to tile is not necessary & is not a good idea, apart from the weight restriction, you will have to wait at least 10 days for it to dry before you can tile. Your better off using a cement powder adhesive, which you may need if intending large format tiles anyway or a quickset render. Forget the pre-mixed one coat crap, it will give you nothing but grief & don’t use base plaster to fill out, it’s not a suitable tile base. For the area above the tiles, mark a line where your tiles will come to & get your plasterer to skim down to it & blend in just below the line; do this before you tile. You will need as flat a tile base as possible particularly with large tiles so remove the old tile adhesive.

When tiling or re-tiling, there are many things that can catch you out. With walls, you need to consider tile weights, prep & materials & suspended timber floors need special consideration. I would advise you read the Tiling Sticky & Forum Archive posts before doing any work or buying materials, it could prevent you making disastrous & potentially expensive mistakes. It’s also 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.

You know i never knew about certain weights for tiling. Ive been a plasterer for years, and have done some tiling too. Obviously if they weigh a ton then id think again. So the limit is 18k per sq m? My brick tiles weigh about 5 or 6k a sq m.

I suppose it could just rip the plaster/face of the plasterboard off if its too heavy.

 

[broontroot]

Richard, not what i wanted to hear, but much appreciated,cheers.

My tiles would be 48cm x 30cm (19"x12")approx, 9mm thick.
I dont think they would be anything near 18kg/sq metre to be honest.

Are you saying i wouldn't need to actually plaster the bare bits you can see in the pics, do you mean i would just use thicker tile adhesive to build it up to the level of the existing plaster?

The old shower unit will also be getting removed, and a new one fitted, and i'd say 50% of the tiled area sounds hollow, so almost likey that the ' outer coat/top coat'(if thats what its called, will pull away from the wall with the tiles ,just the same as in the pics above the bath.

 

[Richard C]

You know i never knew about certain weights for tiling. Ive been a plasterer for years, and have done some tiling too.

It’s surprising how many plasterers don’t know about it; in fact I’ve been plastering longer than tiling & I wasn’t aware of it until I started tiling! It wasn’t really important years ago when 6” x 6” tiles were considered large but with the modern trend towards larger & heavier tiles (some are more like paving slabs), it’s more of a problem. Once you go over around 250mm, you also need to consider using powder adhesive & plaster/plasterboard then needs priming to avoid a reaction between the cement in the adhesive & gypsum in plaster.

Obviously if they weigh a ton then id think again. So the limit is 18k per sq m? My brick tiles weigh about 5 or 6k a sq m.

The weight limit for finish plaster is 20 kg/sqm but that include up to 4 kg/sqm for adhesive & grout; there is probably a safety margin & I guess this to be around 10% (but I don’t actually know) so this is where my figure of 18 kg/sqm comes from. Raw plasterboard has a higher limit of 32 kg/sqm which is sufficient for most tiles but for really heavy tiles you need to go to a render base (40 kg/sqm) if you can afford to wait up to 4 weeks for it to dry (or use a quickset render) or fix tile backer boards which will take you all the way up to around 55 kg/sqm or even higher. All the weight limit figures are published by British Gypsum. quality tile adhesive manufacturers & the Tile Association who have undertaken tests.

I suppose it could just rip the plaster/face of the plasterboard off if its too heavy.

It can happen & you end up with a wall looking much like the OP’s.

 

[peaps]

You will have to re-think the whole job if you are going for a tile that size. You have old lime based render on the wall that will fail before long.

 

[Richard C]

My tiles would be 48cm x 30cm (19"x12")approx, 9mm thick.
I don’t think they would be anything near 18kg/sq metre to be honest.

They are large format & at 9mm thick, may well be near or over the limit; they could weigh anything up to around 23 kg/sqm, depending on tile quality & material. You should find out what they actually weigh before going any further & with lime based render, I agree with peaps, it’s not suitable for heavy tiles & you really need to upgrade the tile base or pick a lighter tile.

You must use cement powder adhesive for tiles that size & thickness, don’t attempt to use tub ready mix, it will take an age to set & sometimes doesn’t; your tiles will move around & may even end up on the floor. Plaster must also be acrylic primed before using powder addy.

Are you saying i wouldn't need to actually plaster the bare bits you can see in the pics, do you mean i would just use thicker tile adhesive to build it up to the level of the existing plaster?

You can normally use cement powder adhesive to fill out & level just before you tile; you don’t need a good finish as in plaster, it just needs to be flat. With that size of tile you will need a very flat base or they will be all over the place; but it's a bit irelevant if the lime reder has to come off

You need to use a thick solid base notch trowel not the usual 6 x 6mm square notch wall job.

The old shower unit will also be getting removed, and a new one fitted, and i'd say 50% of the tiled area sounds hollow, so almost likey that the ' outer coat/top coat'(if thats what its called, will pull away from the wall with the tiles, just the same as in the pics above the bath.

If it’s hollow it’s had it; normally if the render underneath is sound, you can tile straight onto that after a little dressing but if you have a lime base render it will have to come off. If so, the easiest option is usually to board out & tile that but don’t use plasterboard (which should be moisture resistant in bathrooms) in wet areas (shower & around bath), use a waterproof tile backer board. All boards should be mechanically fixed if tiling over, don’t just rely on dot & dab adhesive or the whole lot could end up on the floor.

As I said, take some time to read the Tiling Sticky & Tiling Forum archive posts to avoid making disastrous & potentially expensive mistakes. Post the Tiling Forum if you need more specific advice.

 

[joe-90]

I've never seen tiles fall off due to weight issues - ever. I've taken tiles off that have been there for decades - yet you could pull them off with your fingers - yet they never fell off. The weight of the tile is downward - and the only thing downward is the floor - where do you expect them to go Richard? Sink into the floorboards? Tiles will stand up on their own with a bit of blue tack at the back,. Try it.

 

[huddsspread]

he is only telling us what the regs probably say, 18kg per sq m. You may get away with more, but 18kg on a sqm sounds really heavy for a small place to me.

I also (which is wrong) in my bathroom got bored waiting for adhesive to go off, so i stuck them on with gripfill.....

 

[peaps]

he is only telling us what the regs probably say, 18kg per sq m. You may get away with more, but 18kg on a sqm sounds really heavy for a small place to me.

I also (which is wrong) in my bathroom got bored waiting for adhesive to go off, so i stuck them on with gripfill.....

Joe is correct about the weight distribution, 20 kg of tiles on the wall will not weigh 20kg per square meter.

 

[peaps]

I agree with peaps, it’s not suitable for heavy tiles & you really need to upgrade the tile base or pick a lighter tile.

Lime render that is degrading that is..

 

[broontroot]

Thanks for all the advice.

The tiles we were goin to buy work out at 18.75kg /square metre, a bit over the figures stated. I had no idea they would be so heavy.

I'd really like to work with what i've got, i certainly don't fancy/couldn't afford to take the lime render off,and start from scratch, so it looks like i'm needing lighter tiles.
Surely though a square metre of large size tiles weighs the same as a square metre of smaller sized tiles? I imagine smaller tiles are thinner,and therefore not as heavy.

Right, assuming i buy smaller lighter tiles, what next?
Do i treat the exposed lime render with something before tiling to seal it ?

Or, do i just use 'cement powder adhesive', without sealing the exposed lime render, ie, spread it on over the existing sound plaster and the exposed lime render?
Have a look at the pics in my post above to see what it looks like,........oh,and thanks again lads, much appreciated !

 

[joe-90]

Did your existing tiles fall off? Is that why you are replacing them? Did they take some effort to get off? Did you find they slide down the wall when you touched them? Well why do you think your new ones will? It's manufacturers covering their ass and nothing else.

 

[Richard C]

I've never seen tiles fall off due to weight issues - ever. I've taken tiles off that have been there for decades - yet you could pull them off with your fingers - yet they never fell off.

The weight of the tile is downward - and the only thing downward is the floor - where do you expect them to go Richard? Sink into the floorboards? Tiles will stand up on their own with a bit of blue tack at the back,. Try it.

You’re obviously in one of your moods this afternoon joe So you think I make all this stuff up; for what possible reason? FFS give me a break! I’d been plastering for a couple of years or so & then started into bath/shower rooms including tiling around 2006 &, I can assure you, I was equally surprised to learn about the weight limits for various substrates. When folks had the of 6” x 6” x ¼” "Crystal" tiles of yesteryear it wasn’t a problem but when they started demanding much bigger tiles & 60 x 30 x 1cm tiles started falling off the wall perhaps BG, all the (decent) tile adhesive manufacturers & the Tiling Association decided to do extensive tests to find out why; & then just made it all up for the sheer hell of it

I don’t write the manufacturers technical specs &, starting from very little experience, I just followed them when I started doing this around 2006. Quiet honestly, I have no desire to prove them wrong, invalidate my product warranty & have to pay to fix a failure myself; I’ve never had a failure or intend having one. If you or anyone else wants to ignore the tech stuff that’s your prerogative, “frankly my dear I don’t give a damn”; your choice!

But don’t take my word for it go check it out for yourself, you or anyone else are quiet at liberty to do so & prove me, BG, BAL, Mapei, Webber, etc etc & the TA wrong. This info is widely available on the net from various sources but, better still, ring one of the technical help lines & get a definitive answer. Good luck

 

[Richard C]

Thanks for all the advice.

The tiles we were goin to buy work out at 18.75kg /square metre, a bit over the figures stated. I had no idea they would be so heavy.

I'd really like to work with what i've got, i certainly don't fancy/couldn't afford to take the lime render off,and start from scratch, so it looks like i'm needing lighter tiles.
Surely though a square metre of large size tiles weighs the same as a square metre of smaller sized tiles? I imagine smaller tiles are thinner,and therefore not as heavy.

Right, assuming i buy smaller lighter tiles, what next?
Do i treat the exposed lime render with something before tiling to seal it ?

Or, do i just use 'cement powder adhesive', without sealing the exposed lime render, ie, spread it on over the existing sound plaster and the exposed lime render?
Have a look at the pics in my post above to see what it looks like,........oh,and thanks again lads, much appreciated !

I'll come back later if your still interested but, frankly, I've had enough of it for the minute