Advice Required - Material Spec

[James M]

I'm looking for advice on product regarding a bathroom installation.

I'm unsure at the moment whether the tile will be ceramic or porcelain.

I've currently got an 18mm moisture resistant chipboard screwed @ 150-300mm centres to joists and noggins.

I've been advised that laying a self levelling flexible screed, followed by 12mm hardibacker/cementitous board and screwed to floor while screed is still wet. Scrim tape joints in hardibacker @3mm and fill with flexible waterproof adhesive.

Could anyone advise if this is good advice as I seen to be getting mixed feedback from suppliers?

Would a self levelling waterproof screed be required above the hardibacker to act as the DPM?

Can anyone recommend product for this?

Cheers, Jim

 

[hmtiling]

Hardie fixed to spec then levelling compound. Not sure whay a dpm would be needed. If a wet room use a tanking compound or waterproof memrane

 

[acaciaguy]

Is self levelling needed after the Hardie if floor is level?

 

[Andy Rhodes]

You could forget the levelling compound screw down the hardiebacker the tank all the joints with Ardex WPC ,had the Ardex rep in a couple of weeks ago and said they were compatible

 

[Dumbo]

Are you doing a wet room?
You should be fixing the Hardie on flexible adhesive and tape ing the joints using an alkali resistant Scrim tape and then trowelling over the scrim to a width of 150mm using the flat edge of the trowel . Oh and screw the boards as well .

 

[Old Mod]

screw down the hardiebacker the tank all the joints with Ardex WPC ,had the Ardex rep in a couple of weeks ago and said they were compatible

Sorry Andy, can you explain why you would do it that way please?

 

[James M]

Its not a wet room. Expecting typical water splashes from bath/shower screen etc.

When using adhesive what's the best product used to prep the chipboard. I've read on here that SBR/Febond etc is not advisable?

Is the hardibacker/tanking to the joints sufficient protection from water penetration.

Thanks for the advice.

 

[One Day]

Utterly bizzare way round.
Must have been a builder involved ...

 

[hmtiling]

You could forget the levelling compound screw down the hardiebacker the tank all the joints with Ardex WPC ,had the Ardex rep in a couple of weeks ago and said they were compatible

Are you aware hardie isn't waterproof?

 

[acaciaguy]

I would fix the hardie on flex addy which should also help get level (Within reason ).

Scrim and trowel joints. Tank in wet room or better use non cement board. Tile with a flex addy

Are there any level issues?

 

[Andy Rhodes]

sorry I would screw the backer broad to the floorboards then Ardex WPC on the internal corners & tape the joints also. is what you wanted me to explain,3 fall

 

[Old Mod]

sorry I would screw the backer broad to the floorboards then Ardex WPC on the internal corners & tape the joints also. is what you wanted me to explain,3 fall

No Andy, I was wondering why you would only tank joints and transitions with WPC?
As Harry said, (above) HB isn’t waterproof, surely it’d be a waste of your effort and money.

 

[acaciaguy]

Also I believe hardie should be
Fitted like this
• Apply a supporting bed of mortar or modified thinset to subfloor using a 1/4” square-notched trowel.
• Embed HardieBacker cement board firmly and evenly in the wet mortar.
• Use the fastener pattern as a guide. Fasten HardieBacker cement board with specified nails or screws (as listed in “Materials Required”) every 8” over the entire surface. Keep fasteners between 3/8" and 3/4" from board edges and 2" from board corners.

 

[Old Mod]

Also I believe hardie should be
Fitted like this
• Apply a supporting bed of mortar or modified thinset to subfloor using a 1/4” square-notched trowel.
• Embed HardieBacker cement board firmly and evenly in the wet mortar.
• Use the fastener pattern as a guide. Fasten HardieBacker cement board with specified nails or screws (as listed in “Materials Required”) every 8” over the entire surface. Keep fasteners between 3/8" and 3/4" from board edges and 2" from board corners.

Who’s been read the American spec then?

 

[acaciaguy]

Maybe