Tile weight limits on plaster

[Colour Republic]

Ok so we know tile weight limits on plaster is 20kg per sqm... or is it????

I've had a 'conversation' with someone about weight limits on plaster which made me look up data sheets to back me up. What i've found has left me unsure.

The formula i've worked to is

Tile + Adhesive should be = or less than 20kg sqm.

But on checking British Gypsum's website (let's be truthful, most of the the plaster is from them) I came across the following

Tiling:
Tiles up to 20kg/m2 can be applied to directly to Thistle Multi-Finish, except where the system includes a bonding agent. As the total weight limit of tiles and plaster applied over a bonding agent is limited to 20kg/m2, consideration should be given to tiling directly over to the background. If plastering to provide a background for tiles, avoid polishing the surface. Polished plaster surfaces should be roughened and a suitable primer used.

So lets take a few snipets...

Tiling:
Tiles up to 20kg/m2 can be applied to directly to Thistle Multi-Finish, except where the system includes a bonding agent.

I read this as... If the plaster is applied over a bonding agent, then the total weight limit of 20kg/m2 is to include the weight of plaster.

So the formula would be modified to:

Tile + Adhesive + Plaster should be = or less than 20kg sqm.

Now looking at the data sheets, it says the dry set weight of plaster @ 2mm is 3.4kg/m2, that takes the weight limits of Tile + Addy down to 16.6kg/m2. I know all situations on refurbs are different and these are only guidelines but still the plaster weight adds up to what we would normally use on addy right?

so if the above quote is right then multi-finish without the use of a bonding agent is still

Tile + Adhesive should be = or less than 20kg sqm.

But if the plaster is applied with bonding agent, then it should be

Tile + Adhesive + Plaster should be = or less than 20kg sqm.


The next part of the quote could be interpreted as one of two things:

Tiling:
...consideration should be given to tiling directly over to the background. ...

either, consideration should be given to tiling on to the background plaster, OR not doing any plastering at all and tiling on to the substrate to start with.

We know background plaster shouldn't be plastered on to (execpt for one), Gyproc say this in another data sheet

Tiles should not be applied directly to Thistle undercoats, with the exception of Thistle Dri-Coat

Gyproc Dri-coat is a cement based undercoat, which explains why it would exclude it from the above statement.

Sooooooo... Discuss

 

[White Room]

Yes, tile weight should be less than 20kg m2 because of the powdered adhesive weight with larger tiles but smaller tiles weight could be increased.

 

[Colour Republic]

Yes, tile weight should be less than 20kg m2 because of the powdered adhesive weight with larger tiles but smaller tiles weight could be increased.

Sorry WB you may have missed my point, from the data sheets it states that the weight of plaster (if a bonding agent is used) should be included in the weight limit of 20kg/m2

 

[Dan]

A brilliant thread. This will teach a lot of the noobs. Nice post CR. I've added to your reputation.

 

[Dan]

It's already ranking too.

 

[Colour Republic]

It's already ranking too.

You're such a geek :rofl:


(ok, I know that's pot, kettle, black, but I don't care)

 

[DHTiling]

Yep a good post and I've upped your reputation as well..

Have you checked any other suppliers for info on this weight ratio..?

 

[White Room]

Sorry WB you may have missed my point, from the data sheets it states that the weight of plaster (if a bonding agent is used) should be included in the weight limit of 20kg/m2

I'm with you now Rob, I new that pva was only up to 20kg and plaster at 2-3mm was a minimal weight but a float and set with bonding with pva as a sealer could reduce the weight some what.

Good point there mate.

 

[Alan.P]

Mmmmm, cat amongst the pigeons, can I suggest to a mod / admin that this is moved out of public view before a stampede, at least while we talk about it.

 

[DHTiling]

Good idea Alan.. moved to arms for now..

 

[Alan.P]

Thanks mate, this could be a potential law suit for many a fixer, there is a lot to be talked about, we may need some input from certain manufactures or links to their data sheets, but it doesn't bear thinking about............... but it does. Have we / are we giving bad advice, and have we been fixing to under spec substrates ??

the mind boggles.

 

[Colour Republic]

Yep a good post and I've upped your reputation as well..

Have you checked any other suppliers for info on this weight ratio..?

No, not yet. TBH I can't think of many suppliers and I can't seem to find a datasheet for Knauf FP90

 

[Colour Republic]

Thanks mate, this could be a potential law suit for many a fixer, there is a lot to be talked about, we may need some input from certain manufactures or links to their data sheets, but it doesn't bear thinking about............... but it does. Have we / are we giving bad advice, and have we been fixing to under spec substrates ??

the mind boggles.

I ment to put links to the source in the opening post

Multi-Finish - Broken Link Removed

Bonding - Broken Link Removed

I believe Hardwall, Tough coat and browning all have the same specs re tiling as Bonding

Dri-coat - Broken Link Removed

Now on the Dri-coat data sheet it doesn't say what the weight limit is when tiled directly to Dri-Coat. It says the same as the data sheet on multi-finish but the important words are 'Tiles up to 20kg/m2 can be applied directly to Thistle finish...', as Dri-coat isn't a 'finish' it's an undercoat, then I assume the weight limit might be different?

 

[DHTiling]

Ok.. I have emailed the TTA to get them to clarify this with BS 5385 standards and british gypsum.. something is wrong and needs amending ASAP..

 

[Gazzer]

Nice one Dave, all very confusing IMO