Tiling overboarded bathroom walls

After removing the old sanitaryware, and because the original plaster was in poor condition, we cleaned off our bathroom walls as best we could and employed someone to overboard and skim them. He was aggressive, did a very poor job on the separate loo we had asked him to wet plaster, caused secondary damage during the job, and has since disappeared. Hopefully someone has taken their revenge on him!

My concern now, especially as my wife has her heart set on some beautiful and rather heavy 90 x 30 tiles, is what sort of job he may have done in bonding the panels to the wall, and even if that is up to the job, will the plaster skim take the weight?

I realise there is unlikely to be any non-destructive test in this situation, but professional tilers must face a similar dilemma from time to time and am hoping to get some advice here. I don't want the wall to fall on the plumber, I have enough problems without that

Bad news I'm afreaid, it wont; raw plasterboard (which should be Moisture resistant) will take a maximum weight of 32kg/sqm, if you skim it, the max weight drops to just 20kg/sqm & that includes up to 4 kg/sqm for the adhesive & grout which must be cement powder based for anything much bigger than 250mm. You need to check the tile weigh but I can see even unskimmed PB taking tiles that size; if your tiling it’s not necessary or even a good idea to skim new boarding. But for tiles that size, you need a suitable tile backer board & tile directly into that; depending on which you use they will accept up to 50kg/sqm or more. Unless you reduce you tile weight down to around 16 kg/sqm, you’re in a bit of a fix I’m afraid & if your unsure of the bond to the wall you should certainly add some mechanical fixings, I would not rely on dot & dab to support that sort of tile weight. Unfortunately you should have done a lot more research (read the tiling sticky & forum archive posts) before you started & if you want to stick with those paving slabs on the wall, I would advise to rip the PB down & start again with a quality tile backer board. You should be using this in wet areas anyway, even MR PB is not suitable & won't last unless it's tanked.

Thank you RichardC for confirming what, in my heart, I already knew. However I don't think it's realistic of you to expect homeowners who are employing so-called 'professionals' to research for themselves every aspect of every job. This wasn't a VAT avoiding cash-in-hand job, and our tiling intentions were explained to the guy beforehand. Having done that you should then be able to rely on him to do whatever the job requires. Sadly though, in third rate Britain, this sort of thing is all too commonplace.

B91 said:

this sort of thing is all too commonplace.

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Unfortunately it seems so & is why I always advise anyone having work done to undertake some basic research on what’s involved, get advice, get references & check out previous work before shelling out hard earned cash. It may sound surprising but it’s fairly common for some tradesmen not to fully understand the materials they are using or to appreciate the requirements of others following on; it happens all the time.

Caveat Emptor is prudent, even more so in today’s economic climate where there are so many chancers around who are maybe not what they say they are & it’s very easy to get caught out.

If you post more details of exactly what it is your doing, I & the other regulars will give you all the help & advice you need but you need to cinsider every aspect of the job before you start to avoid getting it wrong.

Richard C said:

Bad news I'm afreaid, it wont; raw plasterboard (which should be Moisture resistant) will take a maximum weight of 32kg/sqm, if you skim it, the max weight drops to just 20kg/sqm & that includes up to 4 kg/sqm for the adhesive & grout which must be cement powder based for anything much bigger than 250mm. You need to check the tile weigh but I can see even unskimmed PB taking tiles that size; if your tiling it’s not necessary or even a good idea to skim new boarding. But for tiles that size, you need a suitable tile backer board & tile directly into that; depending on which you use they will accept up to 50kg/sqm or more. Unless you reduce you tile weight down to around 16 kg/sqm, you’re in a bit of a fix I’m afraid & if your unsure of the bond to the wall you should certainly add some mechanical fixings, I would not rely on dot & dab to support that sort of tile weight. Unfortunately you should have done a lot more research (read the tiling sticky & forum archive posts) before you started & if you want to stick with those paving slabs on the wall, I would advise to rip the PB down & start again with a quality tile backer board. You should be using this in wet areas anyway, even MR PB is not suitable & won't last unless it's tanked.

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some parts i agree with you R.C but on others i am abit confused.

You mention the weight plasterboard/skim can hold per sq/m and i would agree if perhaps you were to tile on a wall that is out of plumb.

But, technically (what i have been taught) if said walls are plumb or close to then surley you could have close to a tonne (not bang on a tonne but you'll know where i am coming from) per sq/m.

I know you know your stuff but would ye not agree? Even if said tiles were to be staggered/brick effect, if not how come?

WestmidsChippy said:

some parts i agree with you R.C

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Well that’s good

WestmidsChippy said:

but on others i am abit confused.

You mention the weight plasterboard/skim can hold per sq/m and i would agree if perhaps you were to tile on a wall that is out of plumb.

But, technically (what i have been taught) if said walls are plumb or close to then surley you could have close to a tonne (not bang on a tonne but you'll know where i am coming from) per sq/m.

Click to expand...

Whoever taught you that is wrong. The maximum weight you can hang off any substrate varies dependant on what it is, here is a list for your reference;

The following table offers general guidance to some common types of building board and the maximum recommended weights for tiling.

Wall Substrates Maximum Weight of Tiling per m²

Gypsum Plaster 20Kg/m²

Gypsum Plasterboard Direct (without a plaster skim) 32Kg/m²

Plywood (WBP) Up to 30Kg/m²

Lightweight Tilebacking Boards* Up to 40Kg/m². Dependant upon the type and thickness of the board.

Glass reinforced Cement Sheets Up to 50kg/m², Dependant upon the type and thickness of the board.

Gypsum Fibre boards Approximately 35- 40Kg/m²

Tile and Adhesive Weight Per Square Metre

Weight per sq metre (Kg) for 3mm thin bed solid bed adhesive

application Weight per sq metre (Kg) for 6mm thick bed solid bed adhesive application

6mm thick glazed tile 14.26 Kg/m2 18.46 Kg/m2


8mm thick glazed tile 17.62 Kg/m2 21.82 Kg/m2


10mm thick glazed tile 20.97 Kg/m2 25.17 Kg/m2


12mm thick glazed tile 24.32 Kg/m2 28.52 Kg/m2


12mm thick quarry 26.40 Kg/m2 30.06 Kg/m2


10mm thick porcelain 23.88 Kg/m2 28.09 Kg/m2


12mm thick porcelain 27.82 Kg/m2 32.00 Kg/m2


10mm thick natural stone 31.10 Kg/m2 35.30 Kg/m2


12mm thick natural stone 36.48 Kg/m2 40.68 Kg/m2


20mm thick natural stone 58.00 Kg/m2 62.20 Kg/m2



Tiles of over 8mm thick should not be fixed to plaster (maximum

permitted weight is 20Kg/m2), however all the tiles above could be fixed
to Marmox tile backer board.

Maximum Permitted Weights

These are maximum permitted weights per m2 of tiles and adhesive combined:

Plaster 20kg/m2

Plasterboard 32kg/m2

Render 40kg/m2

Marmox Tile Backer Board 62kg/m2

WestmidsChippy said:

I know you know your stuff but would ye not agree? Even if said tiles were to be staggered/brick effect, if not how come?

Click to expand...

Erm no; the above is a comprehesive list but here are some reference links for you specifically concerning plasterboard/plaster;

http://www.british-gypsum.com/pdf/SB07_Tiling_02.pdf
page 449:

http://www.bal-adhesives.co.uk/technical/faq#q7

http://www.thetilesource.co.uk/advice/planning-preparation.html
scroll down to wall tiling preparation.

There are many, many more references if you care to search. It’s not an opinion I’m expressing here it’s fact & what the various manufacturers publish on their data sheets; do you think I make this stuff up as I go along

Richard C said:

WestmidsChippy said:

some parts i agree with you R.C

Click to expand...

Well that’s good

WestmidsChippy said:

but on others i am abit confused.

You mention the weight plasterboard/skim can hold per sq/m and i would agree if perhaps you were to tile on a wall that is out of plumb.

But, technically (what i have been taught) if said walls are plumb or close to then surley you could have close to a tonne (not bang on a tonne but you'll know where i am coming from) per sq/m.

Click to expand...

Whoever taught you that is wrong. The maximum weight you can hang off any substrate varies dependant on what it is, here is a list for your reference;

The following table offers general guidance to some common types of building board and the maximum recommended weights for tiling.

Wall Substrates Maximum Weight of Tiling per m²

Gypsum Plaster 20Kg/m²

Gypsum Plasterboard Direct (without a plaster skim) 32Kg/m²

Plywood (WBP) Up to 30Kg/m²

Lightweight Tilebacking Boards* Up to 40Kg/m². Dependant upon the type and thickness of the board.

Glass reinforced Cement Sheets Up to 50kg/m², Dependant upon the type and thickness of the board.

Gypsum Fibre boards Approximately 35- 40Kg/m²

Tile and Adhesive Weight Per Square Metre

Weight per sq metre (Kg) for 3mm thin bed solid bed adhesive

application Weight per sq metre (Kg) for 6mm thick bed solid bed adhesive application

6mm thick glazed tile 14.26 Kg/m2 18.46 Kg/m2


8mm thick glazed tile 17.62 Kg/m2 21.82 Kg/m2


10mm thick glazed tile 20.97 Kg/m2 25.17 Kg/m2


12mm thick glazed tile 24.32 Kg/m2 28.52 Kg/m2


12mm thick quarry 26.40 Kg/m2 30.06 Kg/m2


10mm thick porcelain 23.88 Kg/m2 28.09 Kg/m2


12mm thick porcelain 27.82 Kg/m2 32.00 Kg/m2


10mm thick natural stone 31.10 Kg/m2 35.30 Kg/m2


12mm thick natural stone 36.48 Kg/m2 40.68 Kg/m2


20mm thick natural stone 58.00 Kg/m2 62.20 Kg/m2



Tiles of over 8mm thick should not be fixed to plaster (maximum

permitted weight is 20Kg/m2), however all the tiles above could be fixed
to Marmox tile backer board.

Maximum Permitted Weights

These are maximum permitted weights per m2 of tiles and adhesive combined:

Plaster 20kg/m2

Plasterboard 32kg/m2

Render 40kg/m2

Marmox Tile Backer Board 62kg/m2

WestmidsChippy said:

I know you know your stuff but would ye not agree? Even if said tiles were to be staggered/brick effect, if not how come?

Click to expand...

Erm no; the above is a comprehesive list but here are some reference links for you specifically concerning plasterboard/plaster;

http://www.british-gypsum.com/pdf/SB07_Tiling_02.pdf
page 449:

http://www.bal-adhesives.co.uk/technical/faq#q7

http://www.thetilesource.co.uk/advice/planning-preparation.html
scroll down to wall tiling preparation.

There are many, many more references if you care to search. It’s not an opinion I’m expressing here it’s fact & what the various manufacturers publish on their data sheets; do you think I make this stuff up as I go along

Click to expand...

Brilliant post there Richard, with very accurate facts, data information/references. Gcol would be proud of ya!!

Richard C said:

WestmidsChippy said:

some parts i agree with you R.C

Click to expand...

Well that’s good

WestmidsChippy said:

but on others i am abit confused.

You mention the weight plasterboard/skim can hold per sq/m and i would agree if perhaps you were to tile on a wall that is out of plumb.

But, technically (what i have been taught) if said walls are plumb or close to then surley you could have close to a tonne (not bang on a tonne but you'll know where i am coming from) per sq/m.

Click to expand...

Whoever taught you that is wrong. The maximum weight you can hang off any substrate varies dependant on what it is, here is a list for your reference;

The following table offers general guidance to some common types of building board and the maximum recommended weights for tiling.

Wall Substrates Maximum Weight of Tiling per m²

Gypsum Plaster 20Kg/m²

Gypsum Plasterboard Direct (without a plaster skim) 32Kg/m²

Plywood (WBP) Up to 30Kg/m²

Lightweight Tilebacking Boards* Up to 40Kg/m². Dependant upon the type and thickness of the board.

Glass reinforced Cement Sheets Up to 50kg/m², Dependant upon the type and thickness of the board.

Gypsum Fibre boards Approximately 35- 40Kg/m²

Tile and Adhesive Weight Per Square Metre

Weight per sq metre (Kg) for 3mm thin bed solid bed adhesive

application Weight per sq metre (Kg) for 6mm thick bed solid bed adhesive application

6mm thick glazed tile 14.26 Kg/m2 18.46 Kg/m2


8mm thick glazed tile 17.62 Kg/m2 21.82 Kg/m2


10mm thick glazed tile 20.97 Kg/m2 25.17 Kg/m2


12mm thick glazed tile 24.32 Kg/m2 28.52 Kg/m2


12mm thick quarry 26.40 Kg/m2 30.06 Kg/m2


10mm thick porcelain 23.88 Kg/m2 28.09 Kg/m2


12mm thick porcelain 27.82 Kg/m2 32.00 Kg/m2


10mm thick natural stone 31.10 Kg/m2 35.30 Kg/m2


12mm thick natural stone 36.48 Kg/m2 40.68 Kg/m2


20mm thick natural stone 58.00 Kg/m2 62.20 Kg/m2



Tiles of over 8mm thick should not be fixed to plaster (maximum

permitted weight is 20Kg/m2), however all the tiles above could be fixed
to Marmox tile backer board.

Maximum Permitted Weights

These are maximum permitted weights per m2 of tiles and adhesive combined:

Plaster 20kg/m2

Plasterboard 32kg/m2

Render 40kg/m2

Marmox Tile Backer Board 62kg/m2

WestmidsChippy said:

I know you know your stuff but would ye not agree? Even if said tiles were to be staggered/brick effect, if not how come?

Click to expand...

Erm no; the above is a comprehesive list but here are some reference links for you specifically concerning plasterboard/plaster;

http://www.british-gypsum.com/pdf/SB07_Tiling_02.pdf
page 449:

http://www.bal-adhesives.co.uk/technical/faq#q7

http://www.thetilesource.co.uk/advice/planning-preparation.html
scroll down to wall tiling preparation.

There are many, many more references if you care to search. It’s not an opinion I’m expressing here it’s fact & what the various manufacturers publish on their data sheets; do you think I make this stuff up as I go along

Click to expand...

Ran into the bloke that taught me the trade today, i even mentioned to him a comment made to me by a tiler. his responce was that if i ever were to bump in again with said tiler i should ask him if i get staff discount at tops tiles

I hope one day i can be a super chippy , didn't question your understandings as such etc i am just on the learning curve on becoming a super chippy like the few out there and couple i have noticed on here.

..staff discount at Topps....

half if not more than..dont even know what they are selling or what materials are needed for the job...

as for weight per m2...its not just you, its also builders/plasters also...but they all want to earn that small bit extra,with work that doesnt need doing(i.e. bathrooms/plastering.. it out when they "sometimes know" its not needed).

tictic said:

..staff discount at Topps....

half if not more than..dont even know what they are selling or what materials are needed for the job...

as for weight per m2...its not just you, its also builders/plasters also...but

they all want to earn that small bit extra,with work that doesnt need doing(i.e. bathrooms/plastering.. it out when they "sometimes know" its not needed).

Click to expand...

Click to expand...

Exactly Tic',,, a load of rip off merchants.

WestmidsChippy said:

Ran into the bloke that taught me the trade today, i even mentioned to him a comment made to me by a tiler. his responce was that if i ever were to bump in again with said tiler i should ask him if i get staff discount at tops tiles

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Please accept my apologies if I’ve got you wrong as I’ve been a bit “over done” with smart arse comments over the last couple of weeks so am getting a bit confused & not really sure what your implying. Practically anyone with half a brain can get a discount at most Topps branches (Christ the prices they charge you’ve no option), I don’t have a trade account & only use when no other option but rarely fail. Apart from a few good ones, 90% of them wouldn’t know their asre from their elbow if you asked for advice on tile substrates & maximum permissible tile weights etc. So, pickled brain & all, you’re obviously far too smart for me!

WestmidsChippy said:

I hope one day i can be a super chippy ,

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Keep trying, you never know. I got an O level in woodwork & can build studding, fit doors, architrave & skirting does that qualify me as an ordinary chippy

WestmidsChippy said:

didn't question your understandings as such etc i am just on the learning curve on becoming a super chippy like the few out there and couple i have noticed on here.

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Keep learning, you never know.

Richard C said:

WestmidsChippy said:

Ran into the bloke that taught me the trade today, i even mentioned to him a comment made to me by a tiler. his responce was that if i ever were to bump in again with said tiler i should ask him if i get staff discount at tops tiles

Click to expand...

Please accept my apologies if I’ve got you wrong as I’ve been a bit “over done” with smart a**e comments over the last couple of weeks so am getting a bit confused & not really sure what your implying. Practically anyone with half a brain can get a discount at most Topps branches (Christ the prices they charge you’ve no option), I don’t have a trade account & only use when no other option but rarely fail. Apart from a few good ones, 90% of them wouldn’t know their asre from their elbow if you asked for advice on tile substrates & maximum permissible tile weights etc. So, pickled brain & all, you’re obviously far too smart for me!

WestmidsChippy said:

I hope one day i can be a super chippy ,

Click to expand...

Keep trying, you never know. I got an O level in woodwork & can build studding, fit doors, architrave & skirting does that qualify me as an ordinary chippy

WestmidsChippy said:

didn't question your understandings as such etc i am just on the learning curve on becoming a super chippy like the few out there and couple i have noticed on here.

Click to expand...

Keep learning, you never know.

Click to expand...

Really am not sure what to think on this one.
I am confused in thinking that maybe you are a tiler? or maybe a bloke who on the hourse that can be is also a salesperson aswell as a tiler.

After being on jobs stripping away tiles in kitchen's/bathrooms, spa's etc that have varied on all forms of weight and size of tiles that have been stuck to ordinary plasterboard i stumbled across a few decent tricks of the trade.

just as a reference point on how i have been taught and how to understand my trade aswell as others here is one for ye which i am already sure you know about.
why do you think when cleanly getting behind a tile when stripping of ordinary plasterboard do you think that half of the plasterboard decides to come along with it?

as i said before if a wall is plumb, if there are appropiate fixings into said plasterboard then there is NO reason on this earth (other then a salesperson or a dummy who has been tricked into thinking like a salesperson) that said plasterboard will come off due to the weight of said tiles.

If the wall is not plumb (as in a ceiling or a wall depending on height etc and is nudgeing the 10 degree mark (varies ofcourse which you must understand) then i would agree and stay clear of plasterboard and would only go towards plywood.

Ofcourse there may be other reasons as to why you have decided to copy and paste something you have found off of maybe a manufacturer's website which is why i aint going to go into to much of a rambling stage

But if you do 100% agree with what you spout in all its form then i guess that is why an installer.fitter is now worth as much as a brickie/chippy.

ignoring the bicking side of this post, and for the benifit of the original poster....

the max permissable weights that richard c has posted is absolutely right according to the manufacturers specs. if you go over this load and your tiles fall off you'll have no redress or route for complain.

installers break this rule all the time, and anyone who has tried to remove tiles from plasterboard will tell you that they WONT fall off. the manufacturers are really saying that over 32kg/m plasterboard can split apart and so anything stuck to it will come off, they will have tested this in a lab, and they will be allowing for a tolerance too. the specs dont detail angles or anything although i am inclined to agree with the other poster that if the wall is vertical then the weight in theory goes up. agian though, no manufacturer would back this.

In short, if you go ahead (at your own risk) use a good, trade addy like Bal or granfix. use a powdered addy and follow all the instructions about priming it etc. then have a nice relaxing bath and stop worrying.

Not particularly keen on horses (far from the truth & completely unjustified ) & I’m not a salesperson; I have previously been involved in sales but not the building trade. I can clear up your confusion &, yes, I am a tiler amongst other things but I also have experience in many other areas & have developed many skills over the years which are not just in the Building Trade. It’s an interesting story which I’ve no mind to go into here but, you should be capable of establishing with reasonable accuracy from my profile & archive posts what I’ve done in the past, what I do now & the particular areas I concentrate on now; it’s mainly refurbishment work so I also get to see what’s lurking behind many stripped tile basses.

Having a technical background (previous life), I believe anyone would be foolish to ignore any manufacturers product recommendation, what is the sense in that. It’s not to say that I don’t do it occasionally but that’s not relevant here & there are numerous examples throughout my post history; I’ve even been heavily critiscised for that so it seems you can never win. The bond tile adhesive has to any substrate (& yes being out of plum will affect this as I have stated in previous posts) is what’s holding the tile up & this will be different in each case. As I’ve already said, I don’t make this stuff up but think it would be stupid to blatantly ignore manufacturer’s recommendations; they have to warrant their product does what it says on the tin & have, presumably, carried out tests to arrive at these figures, as have the Tile Association. There will inevitably be a factor of safety in there (I would think at least 10%) & you can sometimes take a calculated risk, dependant on individual circumstances, (you can establish this from another thread I’ve recently posted), the risk of the job failing & the cost of me having to do it all again (it's never happed). I am, however, very uneasy about advising DIY OP’s seeking advise to take unnecessary risks. The only ones who can tell you what the FOS in their data is will be the manufacturer, why don’t you present them with your arguments & ask them to justify their findings.

I really don’t see how my repeating widely published data & posting a couple of website links as a source of reference could possible be justification for trolling/bricking & saying I have no idea what I talking about or have a horse called Trigger. The main one incidentally is just a Word document containing data I’ve collected & not a web link at all. What on earth is your problem

geraint said:

is that what jc quoted.... i hope not....

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Hi geriatric, I honestly hoped you had been banned for a while, disappeared up your own asre or at least would post something constructive on your return . You know I'm not actually quiet sure where I got it from as it was a while ago but you may be right about JTC being the source, I have not checked; but presumably you have or you would not be posting this crap . Even though it would not make him a better tiler (I already said I've no personal experience of him & am disappointed with what’s happened), it doesn't make the data any less accurate . I have no idea where it came from but what data I already knew + other that I have had cause to check I’ve found to be accurate to manufacturers recommendations so, if it was JCT, at least he saved me some time in collating it all; I was (am) appreciative for it. Why do you “hope it’s not so” even if he wasn't who he maybe was making out to be, at least he made a valid contribution.