New (to us) house renovation is presenting it’s first wormhole. My wife has requested a ‘quick’ job in our playroom (strip wallpaper, paint and some LVT on the floor). Of course, being a 100 year old house, things have snowballed slightly to include replastering, new floor and radiator.

Carpet and underlay are both up, but it appears that the floorboards have just been laid (and in some cases nailed?) into a concrete screed. There are signs of moisture – rusted nails, stained floorboards around nail heads and some mould.

My initial reaction is to pull all the floorboards out, put a membrane down and replace the floorboards with chipboard, as a base for the new Amtico vinyl tiles. This will also give me 16 m2 of reclaimed floorboards for our outdoor kitchen project.

Would there be any issues with putting this membrane down, such as trapping moisture? And should the chipboard be stuck down, or will gravity do it’s thing for us? I’ll use the interlocking edge stuff, but I really want to avoid any ‘bounce’ or high spots. Any point in putting a space blanket type insulation layer down?

TLDR; crap solid floor, will a membrane cause issues, should I insulate?

I’d suggest you should rip it all out and insulate, then membrane and then concrete screed. That would be a proper job, but may cause floor level issues with adjacent areas?

Whatever you fit to has to be solid and level. You definitely need a membrane and now you are ripping up, at least some insulation, even if its only 25mm. However from the sound of it you could put down a 25/50mm batten on top of a membrane. 25/50mm insulation between the battens and then a decent thickness ply on that followed by your Amtico.

The most important thing to know when renovating an old house is when you’ve done enough preparation.
There’s always a case to do “just a bit more” – which if you’re not careful will result in a nicely stacked pile of bricks on the lawn, but no house.

Don’t really understand why there’s a concrete floor, with a wood floor on top and a carpet above that. If it’s a concrete floor just put self leveling compound down to make it flat. No need to put wood down again unless it doesn’t work out for levels.

Chipboard is not compatible with Amtico or other LVT. Ply is

It’s shame Wrightyson flounce out, this was his bag.
Agree with above, I’d membrane and subframe with insulation and ply (not chipboard). To be absolutely correct there’s a special grade of ply but I can’t recall the ref. If it’s not too far out, self levelling compound might be way forward. Definitely avoid a rush job / quick fix, it won’t end well when laying Amtico.

The wood isn’t laid on bitumen, is it?

Personally, I wouldn’t lay something impervious like a vinyl flooring over what you have. You probably need to stick with something breathable unless you rip the floor out and replace it with something that has a proper dpc under it. (Non professional opinion)

To be absolutely correct there’s a special grade of ply but I can’t recall the ref.

Diamond ply was often mentioned when discussing the ply and screed for our new LVT flooring last year.

If floor levels in adjacent rooms will work id go for the rockape option drill some test holes to see how thick underfloor conc is dig out to suit then dpm min 50mm insulation, screed over up to reqd level poss latex self levelling to sort last few mm . quick calcs 16m2 x .1 thick 1.6m3 getting on for 3tonne to shift out ( and back in again) good luck. IAAB
Must have been a real Flounce from wrighty, not just a 2 day job like most do. do you have cellars to deal with as well? just a thought so your floor to ceiling height doesnt suddenly rise to 4m

I should have mentioned that I run a commercial interiors business, so we are often faced with sub floor issues, insulation/screed requirements. My advice is based on previous projects.

Regarding the ply….i’d suggest you don’t need anything special, but a 25mm structural ply will be fine over 600mm spaced battens/joists. Clearly you don’t want it to flex, but having rigid insulation under the ply also helps support it.