Recommended floor sealer (liquid DPM), or not?

[Tim S]

Hi,

Took some old vinyl flooring up at the bungalow, and, not surprisingly[1], there were large patched of black mould.

[1] The floor is known to be (by digging a holes): 4" concrete on earth, no DPM, and 1.5-2" sand/cement screed. Vinyl laid direct on screed.

Finally, I have made up my mind what flooring to lay:

Bedrooms: 15-20mm Marmox tilebacker board[2] glued to screed, then floating wood floor on top.

Other rooms: 20-30mm Marmox board, glued down, then ceramic/stone/similar tiles glued with flexible adhesive to Marmox.

[2] Marmox is a closed cell waterproof foam, with both faces finished in polymer+cement impregnated fibreglass mat

the Marmox board will act as a damp barrier (except the joints) and I would glue it down with cementous tile adhesive which isn;t bothered by damp.

So, the question: Do you reckon I would be better off applying a liquid DPM to the screed before sticking this down, or not?

And if so - which one? Most of them (eg Synthaprufe or Aquaseal ) look like they are basically bitmen based - in which case would I be weakening the bond to the Marmox board? Would blinding with sand help?

Or - are there any other products that sink in to the surface of the screed? In the USA, there seems to be some references to a polyuretha/ene DPM - which soaks in - but I can't find anything like that here.

Builders' Merchants round here have loads of Thompson products - but they all seem to be aimed at driveway block sealing, brickwork sealing and suchlike...

Cheers and TIA

Tim

PS - I decoded against the floorheater.co.uk UFH panels. Marmox is stonger, more rigid and I don't have to worry about wasting money to warm the worms.

20-30mm of Marmox will add to the comfort of the floor, and is a guaranteed energy efficiency measure (how much, I don;t know, but at least it's better than now).

[meow2222]

Youre putting down a vapour barrier - why would you want two. The one issue I see is picking a glue for under the marmox that will be ok permanently damp.

NT

[Tim S]

[e-mail] coughed up some electrons that declared:

Belt and braces? I don't know - I was considering the joints, small as they are.

Truth be told, having read up on laying engineered wood - I might just as well put polythene DPM over the top under the wood - that costs practically nothing and does no harm, on the offchance that any vapour does leak through.

That's OK - had it on good authority that plain old cement based tile adhesive (the grey sort you mix from powder) will be fine, damp.

Cheers

Tim

[Stuart Noble]

The marmox should prevent condensation, which may have been the original problem

[Tim S]

Stuart Noble coughed up some electrons that declared:

I hadn't thought of it that way - but that room was never heated much and the floor never gets higher than 15C - the earth base temperature under the slab is around 8-10C by quick and dirty measurement. The floor covering has been down a good 10 years too.

It's not like the slab is actually soaking wet - so it seems that it's more a case of vapour coming through, getting trapped and presumably liquifying as you suggest.

Yep - all things said and done, Marmox (or an identical product - there are a few) is clearly the best thing for this house, with the least risk of going wrong.

Thanks!

Tim

[Stuart Noble]

I have a tiled solid floor, and you can see by the darker colour on the grout lines in certain places that there is always a degree of condensation in the winter.

[meow2222]

a VB is already belt n braces. Lots of floors are ok without one, as long as you dont put an impermeable cover on top.

yes, but you cant glue it, and it doesnt last well.

I wish. Bitumen works. Cement can too.

NT

[Tim S]

[e-mail] coughed up some electrons that declared:

Sorry, don't follow - are you saying I should bitumen the board down?

In the meantime, I phoned Marmox. They said the failsafe solution is to plug and screw the board down then tape the joints and screws and this would be guaranteed to give a DPM as well as an insulating layer.

They said they didn't have anything against using adhesive, but it would be up to an adhesive manufacturer to advise on suitability. I'll ring Mapei now and see what they say...

Cheers

Tim

[Tim S]

Tim S coughed up some electrons that declared:

And the answer was: Keraquick. They said there were no guarantees as to whether the hydrostatic pressure would destroy the bond in X decades, but he reckoned that Kerquick was the most likely to succeed, being cementous and having extra polymers.

Cheers

Tim

[meow2222]

What does it cost compared to a can of bitumen roofing adhesive?

NT

[Tim S]

[e-mail] coughed up some electrons that declared:

Nothing horrendous - it's not a latex mix, though it can be made into one by buying a horrendously expensive admix.

I don't think felt adhesive would have enough gap filling abilities; Marmox is very rigid and even my good floors have a couple of mm variation.

Cheers

Tim

[meow2222]

Bitumen felt adhesive fills bigger gaps than that easily. But it sounds like either would work ok - I cant help but think someone wants your money though, just a gut feeling Bitumen also gives you a 2nd dpm, fwliw.

NT