Hardiebacker onto terracotta hollow tile wall - Tile Advice

[adibell]

Hello,

I’ll start by saying I’m not a pro. Im a DIYer but value doing things the right way.

I’m doing our bathroom, removing all the blown plaster and cleaning up the walls before using [insert appropriate tile backer board here], tanking the joints and tiling onto these.

I was going to use Hardiebacker 6mm boards, using gripfill adhesive, plus mechanical fixings, as shown on the hardiebacker install guides for masonry. However, the two internal walls are terracotta hollow tile block walls rather than brick. SEE HERE FOR EXACTLY WHAT I MEAN, it’s the only place I’ve found info on what the heck they are: Structural Terra Cotta - Structural Clay Tile - http://historicbldgs.com/terra_cotta.htm
They are one chamber thick (see diagram on that page), though the ribbed-for-your pleasure surface runs horizontally, rather than vertically shown in that picture.

I’m concerned that unless I go purely into the mortar joints with the fixings, I won’t get a proper fix onto the walls. Hardiebacker install video states the mech. fixings must go a minimum of 50mm into the masonry. Additionally, the uneven surface of the blocks makes me think the grab adhesive won’t get anywhere near enough contact with the blocks.

Does anyone have any experience with this situation, or could offer any advice please? Battening onto the wall is not an option as the bath would no longer fit between the end walls!!

 

[Tile Fix Direct]

Hello Adibell
I cannot give recommendations for Hardibacker but an alternative would be to use Orbry long boards with dot and dab fixing (possibly with additional fixings using Orbry Spankers);
https://www.tilefixdirect.com/pdf/orbry-solid-wall-fixing-guide.pdf
The advantage would be you would be able to create a flat wall (the Hardibacker fixing would follow the contours of your solid wall), and the Orbry boards are insulated so it would reduce condensation from the cold external walls which in turn would reduce the risk of mould growth. Don't forget to install a fan in the room to remove excess moisture!
Orbry Board - https://www.tilefixdirect.com/product/Orbry-Insulated-Backer-Board

 

[Bill]

Why not remove all the plaster and render the walls in sand and cement then use a tanking system for render........ no need for boards then.

 

[Waluigi]

To give a third option and provided the Tiles don’t exceed the weight limit of 32kg PSM inc Adhesive and Grout, I’d Dot and Dab Plasterboard onto the wall. There’s no need to add mechanical fixings to plasterboard (with the exception of insulated plasterboard) so no need to worry about drilling into your hollow blocks. Wet areas would be tanked as normal.

If the walls do exceed the weight limit then I’d agree with Julian and install the Orbrey system. With a little careful planning you will easily hit the mortar joints where necessary.

 

[WetSaw]

This sort of thing is what most internal ( and some external..) walls are made of over here in Spain. Even ones with a single row of holes take fixings OK. Use decent plugs ( I use Fischer) designed for hollow walls and you'll have no problem.

 

[adibell]

Hi all,

Thank you! Great to see a really helpful community on a forum! There’s a lot of other forums I’ve been on before where things descend into trolling and lectures on just getting someone in to do it for me!

I think using the dot and dab technique is probably best with some tile backer boards. I hadn’t heard of Orbrey before but if anyone who isn’t the sole supplier of the suggested product weigh in on this please? Would Hardiebacker work in the same way; dot and dab, with fixings into the mortar? Is Orbrey actually any better?

I didn’t really want to use plasterboard, it just gives me a bad feeling in wet areas. I was planning on using Hardiebacker boards for the whole tiled area of the room (we’re also having an area of plaster on the opposite walls to the wet area), but is this really necessary? Its quite hard going on the wallet.

 

[adibell]

View attachment 103974

This sort of thing is what most internal ( and some external..) walls are made of over here in Spain. Even ones with a single row of holes take fixings OK. Use decent plugs ( I use Fischer) designed for hollow walls and you'll have no problem.

Here’s a photo of our wall. I was concerned that the walls were too thin, and they’re super brittle. I’ll have a look into the plugs you mention.

 

[Balloo]

To give a third option and provided the Tiles don’t exceed the weight limit of 32kg PSM inc Adhesive and Grout, I’d Dot and Dab Plasterboard onto the wall. There’s no need to add mechanical fixings to plasterboard (with the exception of insulated plasterboard) so no need to worry about drilling into your hollow blocks. Wet areas would be tanked as normal.

If the walls do exceed the weight limit then I’d agree with Julian and install the Orbrey system. With a little careful planning you will easily hit the mortar joints where necessary.

 

[Balloo]

I concur

 

[Boggs]

Plasterboard will be fine in wet areas, you can get 12.5mm moisture resistant plasterboard and then apply a paint on tanking liquid to make it waterproof.

Remember the Hardie boards will still need to be tanked as they are only moisture resistant and not waterproof.

 

[Waluigi]

Hi all,

I hadn’t heard of Orbrey before but if anyone who isn’t the sole supplier of the suggested product weigh in on this please? Would Hardiebacker work in the same way; dot and dab, with fixings into the mortar? Is Orbrey actually any better?

Two very different boards. Personally and completely irrelevant to the forum sponsor being on this thread, I’d still opt for Orbrey. It’s far easier to work with, to manoeuvre and to cut plus the actual board itself is waterproof so would only require tanking at the joints, screw holes and abutments. Hardiebacker is not waterproof, it requires fully tanking and despite what I have heard the reps say, it allows moisture to pass through it. Hardiebacker on a floor area is very good but on walls less so.

There are however some disadvantages with Orbrey and in fact all lightweight foam boards- they require a tighter spacing between timber studs on stud partition walls, mainly on boards 12mm. The thicker boards less so.

In terms of using Plasterboard, it’s absolutoey fine. I’ve been using it in wet areas for a very long time with either a paint on or sheet tanking membrane on top within wet areas. No need to tank in areas outside of the shower/bathing areas.

Just to add- bare plaster in a Bathroom is absolutely fine. Prime the wall with a primer or watered down paint.

 

[adibell]

Great, thanks for more replies. So with regards to using plasterboard, would I face difficulties if my tiles on their own are 20kg/m2? Why would anyone pay a fortune for tile backer boards over the MR plasterboard? Should I still use mechanical fixing with the MR plasterboards?

Additionally, because I hate the void behind plasterboard when using dot and dab, I taught myself to plaster, and use Hardwall plus skim. Would I be better just to use bonding (seeing as the clay tiles will be low suction?) and tank it, then tile onto that? For the plaster only areas, I won’t be dot-dabbing, so should I just brown the whole room? Should I also skim before tiling if that’s the case, or is the basecoat plaster ok to tile onto. I’ve gotten myself confused with so many options now!

 

[WetSaw]

Wedi board or similar foam cored boards are lighter and only need sealing on the seams and screws. Plasterboard is a lot cheaper!

 

[Waluigi]

Are you tiling the bare plaster walls? I assumed these were being painted.

I would always try to tile onto a board rather than plaster, With the exception of smaller, lighter tiles.

 

[adibell]

So I’m tiling up to a waistline all the way around the room, then full height above the shower bath, like the attached image (the bare painted plaster bit in white obviously).

So I’d have to plasterboard/tile backer board most of the room, but then I’ll do browning plaster for the bare plaster bit. I’ve looked at Fischer plugs and would be happy using these as mechanical fixings in the hollow clay bricks, now I just need to decide whether I use tile backer boards, or WR plasterboard...plasterboard is cheaper, but additionally, I lose 12.5mm+ dotdabs, which I can’t then actually fit between the ends of the bath and the end walls....the bath is 1700mm, and the opposing walls are 1720 apart!