replaing broken plaster after removing tiles??

I've been given the task of refitting our bathroom with new tiles/suite. I've removed some of the old tiles but in some sections its removed the top skim of plaster, but other sections (some 12" x30" oval) its removed all the backing plaster back to the original brick wall. It looks like the backing plaster was a good 12/15mm. Couple pics below (I will be removing all the tiles in over the next couple days)

I'm just wondering what the best method to repair this is. Two routes I think (with questions)

1) Repair the plaster using bonding/one coat? back so its all level again. My only issue with this is I think it will be 2+? weeks before I will be able to tile on it due to waiting for it to dry out. If I used bonding plaster would I need to pva the brick/existing plaster?

2) Plasterboard over the existing remains using dot and dab and then tile directly onto the plasterboard (or does it still need a plaster skim?

Cheers for any advice

Personally, I would go down the bonding route which will give you a good solid background to tile on. Use diluted PVA to seal the existing and give a bit more adhesion for the bonding - although it doesn't need much help!

If you can't wait for it to dry you can use the dot an dab method to fix boards but tilers will advise you to use something like aquaboard rather than standard plasterboard.

Might be worth asking a question or two in the tiling forum.

misterhelpful said:

Personally, I would go down the bonding route which will give you a good solid background to tile on. Use diluted PVA to seal the existing and give a bit more adhesion for the bonding - although it doesn't need much help!

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Sorry Mr Helpful but that’s not good; Bonding plaster or any of the base coat plasters except Tough Coat are not suitable for tiling directly over. I wouldn’t advise Bonding with a Multi skim as a tile base either due to drying time & tiling weight limits, see info below.

Rob_Quads Sand/cement render is the way to go but that will give you a problem with time as you will have to wait & it’s up to 4 weeks for a base coat, 10-14 days for a skim before tiling can start. On localized repairs it’s common to use powder tile adhesive as this can be tiled over next day either that or you need a quickset render to avoid the time problem. Failing that & if the walls are in a bad way, you can dot & dab Moisture Resistant PB in the dry areas & mechanically fix waterproof tile backer board in wet areas; if you use MRPB in wet areas it should be tanked if you want it to last. Another thing to remember when tiling is that plaster board will only accept a max tile weight of 32kg/sqm unplastered or just 20kg/sqm when plaster skimmed (applies to any plaster skim) & this includes up to 4 kg/sqm for the addy/grout which can be a problem if you’re laying large format tiles. Render in good condition will accept 40 kg/sqm but in some cases only tile backer boards are suitable, the heavy duty ones can go up to 55 kg/sqm +.

Please 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; the cheapo DIY stuff is mostly crap. What size/type of tile are you going to be laying?

Have a read & come back if you need more info but post the Tiling Forum as suggested.

Richard C said:

Sorry Mr Helpful but that’s not good; Bonding plaster or any of the base coat plasters except Tough Coat are not suitable for tiling directly over.

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Phew, glad I suggested asking in the tiling forum now! Cheers Richard.

Out of interest, why is it not suitable - I've seen plasterers patching walls with it ready for tiling several times in the past but never been to see what happens when the tilers arrived?!

misterhelpful said:

Phew, glad I suggested asking in the tiling forum now! Cheers Richard.

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No problem, it’s all about experience. The unfortunate thing is there is not much cross education/understanding between trades these days & unless a “specification” tells someone what to use/do (unlikely with jobbing building work & DIY), they just rely on what they (think they) know. They never think to check (or understand) the manufacturer’s specs or even ask; most won’t give a sheite what is suitable for that which will follow & are only interested in the job rate. I can understand that to a certain extent but it says no interest or pride in what you do!

Amongst other things, I was plastering (which I still do) marginally before tiling & initially made the same mistakes until it was pointed out to me, luckily without any problems & comebacks. For me (my reputation & wallet), it’s all about doing something that will last whilst minimising risk of failure & comebacks on me as much as possible.

misterhelpful said:

Out of interest, why is it not suitable - I've seen plasterers patching walls with it ready for tiling several times in the past but never been to see what happens when the tilers arrived?!

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As I said; rather than bloody mindedness, it’s mostly ignorance of the materials being used & a lack of cross trade education/understanding. TBH, small patching repairs in Bonding (& I’ve done it) won’t make an awful lot of difference unless were talking large/heavy format tiles; but Bonding, along with practically all other base plasters is very soft, highly absorbent unless primed & just doesn’t have the strength to support the weight. The maximum specified tile weight for any plaster base is just 20 kg/sqm(& that includes addy/grout); no problem in days of old when 6” x 6” “Crystal” tiles were the norm but if you start hanging a 600 x 300mm + slate/stone or even ceramic/porc tiles on there, your going to have problems!

The "tilers" following on will most likely not know any different or give a toss anyway. Iit's usualy the poor sod of a punter thats shells out up to £10k for his new bath/shower room who picks up the tab 2/5 years later on a job that should last at least 10 up to 20 years!

Thanks Richard.

You're right about not checking the manufacturers spec - monkey see, monkey do!!

I (and others) will know in future to make sure that a suitable product for the job is being used.

Really appreciate you taking the time to reply.

Thanks M8, nice to have someone who actually listens when they get it slightly wrong rather than get all prickly & defensive.

But don't necessarily take my word for it, check it out for yourself &, by all means, come back & take the pleasure to & kick me in the balls if I'm wrong ; but gently if you've a mind

Nice respectful comments there RichC and Mr H. Good to see. Reminds me of the good old days when the Plastering/Rendering Forum was like that. All we seem to get on there lately is gutter comment when there is a disagreement. Ah well,, we'll get over it.

roughcaster said:

Reminds me of the good old days when the Plastering/Rendering Forum was like that. All we seem to get on there lately is gutter comment when there is a disagreement.

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I've noticed that over the last few days, and was going to post a reply there myself but didn't fancy a hammer in my head - if you get my drift!!

misterhelpful said:

roughcaster said:

Reminds me of the good old days when the Plastering/Rendering Forum was like that. All we seem to get on there lately is gutter comment when there is a disagreement.

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I've noticed that over the last few days, and was going to post a reply ther myself but didn't fancy a hammer in my head - if you get my drift!!

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I know what you mean Mr H. I enjoy reading all your very useful posts.

roughcaster said:

Reminds me of the good old days when the Plastering/Rendering Forum was like that. All we seem to get on there lately is gutter comment when there is a disagreement. Ah well,, we'll get over it.

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You’ve been around here a while RC, you may have noticed that I rarely venture there now except when I spot something which is blatantly wrong. In fact I’ve noticed many of the “original” Forum spreads rarely post now.

Thanks for the comments. Having stripped the main side wall next to the bath I think i am definately going to have to go the route of MRPB and tile backer board.

Not exactly what I planned but would rather get it done so it lasts than use the wrong stuff and find the large expensive tiles falling off the wall.