Rigid LVT tiles onto chipboard floor

danrv

Hi
I'm about to put the top floor down in my bathroom project. The new P5 green chipboard subfloor is level and the tiles are waterproof click type Malmo Marta with built in membrane.
Just wondering if the floor needs any further treatment before laying them.
Any help appreciated.

grumbler

I guess you mean built-in underlay, not membrane. Personally, in a bathroom, I'd possibly add a membrane on the top of the chipboard. With the sides folded up. Just in case.

danrv

grumbler said:

I guess you mean built-in underlay, not membrane. 

Yes sorry, underlay. 

danrv

The Malmo instructions state that the tiles can be installed directly over prepared solid & flat floorboards. 
A membrane would have to be really thin to prevent any give or flexing. Some I've seen is between 2.5mm - 5mm thick.
Something like this might do if overlapped.
https://www.bathroom2kitchen.co.uk/accueil/1880-mapei-waterproofing-sheet-membrane-wp-200-1m-cut-1m-width-044-048mm-thickness-blue-mapeguardwp200-1m-0750122369409.html

grumbler

With an overlap you have to seal  it reliably.

For solid wood planks on a concrete slab I used blue DPM from BnQ (plus thin underlay). 
SF sell similar 3x4m black one - https://www.screwfix.com/p/capital-valley-plastics-ltd-damp-proof-membrane-black-1000ga-3m-x-4m/50464 
Not sure if it's any different for LVT, but, if needed, you you can heat the membrane a little with a hair drier or a heat gun to make is softer when laying the planks.

danrv

grumbler said:

With an overlap you have to seal  it reliably.

For solid wood planks on a concrete slab I used blue DPM from BnQ (plus thin underlay). 
SF sell similar 3x4m black one - https://www.screwfix.com/p/capital-valley-plastics-ltd-damp-proof-membrane-black-1000ga-3m-x-4m/50464 
Not sure if it's any different for LVT, but, if needed, you you can heat the membrane a little with a hair drier or a heat gun to make is softer when laying the planks.

That might do if less than 1mm thick.
There won't be much water getting onto the tiles but it's an extra barrier.
Will need to stick in place around the edges.

grumbler

It's definitely thinner than 1mm, but, possibly,  some wrinkles will be difficult to avoid.

danrv

The builders's membrane has fitted in well and it's turned up around 20mm at the edge. 
I take it that the LVT floor tiles would go close to the edges and then skirting board on top.