Floor and wall prep - sense check please?

[Herbis]

Hi all,

Just about to get going on bathroom reno and would very much appreciate if you could sense check my prep, please. Plan is:

Walls

• Will be going back to brick > Prime with Mapei Primer G > 6mm notched bed of Larsen Pro Flexible FiberFlex for 6mm Hardiebacker, screwed with 9 x 6x60mm screws per board
• Wetroom areas will be primed with Bal APD then have Impey Membrane over. No additional prep on Hardie where there isn't Impey membrane
• All walls will then have Ardex X7G Flexible then 300x600 ceramic tiles

Floors

• Old 18mm ply removed
• 22mm P5 chipboard t&g installed > prime with Mapei Primer G > 6mm notched bed of Larsen Pro Flexible > 6mm Hardiebacker with 12 x 4x25mm screws per board
• Wetroom areas will be primed with Bal APD then have Impey Membrane over. No additional prep on hardie outside of wetroom area
• Ardex X7G Flexible for 300x600 ceramic tiles

Hopefully that makes sense(?)... any tips?

 

[parkerfresh]

Are you using 600x300 ceramics on the floor?

 

[Herbis]

Are you using 600x300 ceramics on the floor?

Sorry - copy and paste job... 600x300 porcelain on the floor

 

[parkerfresh]

Phew, all good then.
You can use 6mm hardie on masonry walls, but it’s good practice to use 12mm, and if it is a wet area, I’d go for 12mm jackoboard instead. I wouldn’t use Larsen adhesive to tile a dog kennel, but that’s just me.

 

[Herbis]

Phew, all good then.
You can use 6mm hardie on masonry walls, but it’s good practice to use 12mm, and if it is a wet area, I’d go for 12mm jackoboard instead. I wouldn’t use Larsen adhesive to tile a dog kennel, but that’s just me.

Yeah I read some reviews about the Larsen after purchasing and it's too late unfortunately. Well... it's not installed yet, but I'd have a lot of it lying around if it wasn't used. Will it be okay to use as it's 'only' going to be used as the gap filler for backer boards?

 

[parkerfresh]

Yeah, it’ll be fine for that, I’m sure it’s fine for fixing tiles, I just don’t use it. I know hardie recommend 12 screws per board aswell, but I’ve always put them in every circular indentation on the 6mm boards, works out to about 33 screws per board off the top of my head, probably overkill but I’ve never had any problems.

 

[Herbis]

Yeah, it’ll be fine for that, I’m sure it’s fine for fixing tiles, I just don’t use it. I know hardie recommend 12 screws per board aswell, but I’ve always put them in every circular indentation on the 6mm boards, works out to about 33 screws per board off the top of my head, probably overkill but I’ve never had any problems.

Great - thanks a lot for your help - I think I'll go towards the 'overkill' option too, can't hurt, can it!

One question that's bugging me... for the 6mm notched adhesive bed below the Hardie, do I need to prime my P5 chipboard first? The last thing I want to do is introduce moisture (in the form of primer or adhesive) to the boards that they can't handle. Equally, I know the bed is only gap filling, but I want it to maintain it's integrity, so want to prime if needed. Issue here is I can't find any manufacturer that will openly recommend using their primer/ adhesive on P5 chipboard as they're scared people will install tiles with it, which is obviously wrong - I just want to make sure I'm doing the right thing for my backer. As above, my plan is either Bal APD or Mapei Primer G (neat or diluted?), then the Larsen flex for the backer

 

[parkerfresh]

I Prime pretty much everything these days, when in doubt… primer out. The moisture from primer should not be able to penetrate p5. The primer and adhesive will go a little way to help bond the hardie to the chipboard, but the screws are doing most of the work.

I’ve pulled up dot n dabbed 600x600 from chipboard a few times and virtually all adhesive came up on the tile… i can understand why non tilers think that waterproof plaster board or timber is suitable to tile straight onto for wet areas, but in truth, it’s not really suitable for tiling in any areas.

 

[Herbis]

I Prime pretty much everything these days, when in doubt… primer out. The moisture from primer should not be able to penetrate p5. The primer and adhesive will go a little way to help bond the hardie to the chipboard, but the screws are doing most of the work.

I’ve pulled up dot n dabbed 600x600 from chipboard a few times and virtually all adhesive came up on the tile… i can understand why non tilers think that waterproof plaster board or timber is suitable to tile straight onto for wet areas, but in truth, it’s not really suitable for tiling in any areas.

Okay great, thanks again - so just neat BAL APD on the chipboard then good to go?

 

[parkerfresh]

Yeah, prime and good to go mate.