Tiling on hardwall - is this a big no no?

[Pothole]

Hello

I'm really hoping someone can help as we are doing 4 bathrooms in our home and everyone is saying different things. Pretty new to this so any advice gratefully received!

We have a 1930s property which has solid brick walls (no cavity). Our builder has hardwalled the bathrooms. Our tiler turned up to have a look and said he cannot tile on hardwall, builder says you can if you apply 3 coats of BAL All in One Plus Primer. Can someone tell me if I can do this or not?

We don't have that much room for moisture boards now and I don't know how they would attach to the hardwall anyway. Our tiles are around 20kg per sq metre without grout (8mm thick porcelain tiles).

Be really grateful for your comments. Thank you

 

[Dave]

When you say hardwall , is this as in browning base coat , ?

 

[Pothole]

It is Thistle Hardwall, an undercoat plaster Gypsum product

 

[Trigger]

You can not tile directly onto Thistle Hardwall. It either needs to be plastered with multifinish plaster (but you have weight issues as plaster can only hold 20kg per square meter) or you need to install moisture resistant plasterboard or a tiling board.

 

[Dave]

It is Thistle Hardwall, an undercoat plaster Gypsum product

Yep as trigger says. It’s a no no. Not suitable to tile to directly

 

[Pothole]

You can not tile directly onto Thistle Hardwall. It either needs to be plastered with multifinish plaster (but you have weight issues as plaster can only hold 20kg per square meter) or you need to install moisture resistant plasterboard or a tiling board.

Thanks Trigger. The builder is arguing that we wont be tiling onto hardwall as there will be 3 coats of BAL All in One Plus Primer on top of the hardwall then we're tiling on top of the primer. I assume this still won't help? If it does, will there be a different weight limit as the hardwall is thicker than plaster skim?
Thanks again

 

[Trigger]

All I can really say is that the manufacturer of the hardwall (British Gypsum) says that it is not suitable to be tiled on. I don’t know of any tiler that would risk it and go against the advice of the manufacturer.

Why risk it at this stage, it will be a lot harder and more expensive to put right if it fails further down the line.

And anyway as hardwall is a backing plaster I believe you would still have the weight issue of 20kg per square metre.

You can download the spec sheet from the British gypsum website where it will clearly state not suitable for tiling.

I think he is trying to fob you off as he has messed up. There was no need to use hardwall in the first place, he should have used a board of some description.

 

[Pothole]

All I can really say is that the manufacturer of the hardwall (British Gypsum) says that it is not suitable to be tiled on. I don’t know of any tiler that would risk it and go against the advice of the manufacturer.

Why risk it at this stage, it will be a lot harder and more expensive to put right if it fails further down the line.

And anyway as hardwall is a backing plaster I believe you would still have the weight issue of 20kg per square metre.

You can download the spec sheet from the British gypsum website where it will clearly state not suitable for tiling.

I think he is trying to fob you off as he has messed up. There was no need to use hardwall in the first place, he should have used a board of some description.

Thanks Trigger - everything you're saying makes sense. Unfortunately the builder is not easy to deal with on this. We don't want to take the risk of it all failing so are trying to think of solutions, to get round this mistake. One thing we thought we could do was to stick and mechanically fix 6mm hardy backer boards to the walls. This does mean having to drill through the hardwall then into the solid brick walls behind. I am not sure how easy this would be though as the builder has been telling us throughout the build how difficult it is to drill into the bricks as they are very hard. Also, we can't see the mortar line due to the hardwall on top. It isn't ideal but just trying to get round the problem of him having put hardwall over all 3 bathrooms....arghhh!!!! Grateful for your comments.

 

[Dave]

Thanks Trigger - everything you're saying makes sense. Unfortunately the builder is not easy to deal with on this. We don't want to take the risk of it all failing so are trying to think of solutions, to get round this mistake. One thing we thought we could do was to stick and mechanically fix 6mm hardy backer boards to the walls. This does mean having to drill through the hardwall then into the solid brick walls behind. I am not sure how easy this would be though as the builder has been telling us throughout the build how difficult it is to drill into the bricks as they are very hard. Also, we can't see the mortar line due to the hardwall on top. It isn't ideal but just trying to get round the problem of him having put hardwall over all 3 bathrooms....arghhh!!!! Grateful for your comments.

Tell your builder to stop messing about and skim it. If he won’t then get it skimmed yourself.
Backing coats are unsuitable.

 

[Trigger]

Did the tiler not offer you any advise on how he/she would advise you proceed? Based on the weight of the tiles and allowing 2-3kg per m2 for adhesive and grout I would go down the route of a 6mm tiling board glued and mechanically fixed as you mentioned. Like you said it needs to be fixed to the brick. As it is a solid wall you might also want to think about stainless steel screws as there is always the possibility of damp.

 

[Huddersfield Tiling]

Never listen to a builder when it comes to tiling.
Tiling work is subject to much more strict regulations than builders follow.
Builders don't care once they have done their bit at a tolerance of +/- 20mm.
The tilers tolerance is +/- 4mm on a suitable substrate over 2m.

 

[Pothole]

Never listen to a builder when it comes to tiling.
Tiling work is subject to much more strict regulations than builders follow.
Builders don't care once they have done their bit at a tolerance of +/- 20mm.
The tilers tolerance is +/- 4mm on a suitable substrate over 2m.

Thanks very much - good point - builder is a bit rough and ready it seems.
The builder is going to quote for fixing the backer boards but anything outside of the original quote is always in the thousands unfortunately...
Can I ask, it sounds like a time consuming job getting the screws into the hard bricks. Would a tiler often be tasked with the job of fixing the backer boards on? I've mentioned it to our tiler and he said to ask the builder first. I didn't know if he wasn't that keen because he's not often having to do it

 

[Trigger]

Each to there own really. I like to do my own prep work as I know it will be done properly. Its not overly difficult to drill through a board into brick, plug it and screw it. A half decent sds drill will fly through it.

 

[Huddersfield Tiling]

So, a quick and cost-effective way of solving the issue is to create a suitable background to receive tiling. Without viewing the walls, I would suggest over-boarding the walls using 12.5mm plasterboard using dry wall adhesive (if suitable to do so). Then use a tanking kit to prepare and make the plasterboard waterproof to accept and fix tiles onto.