Chipboard on battens and polystyrene on concrete in 1980s kitchen

[Schinklegroover]

I've suffered a leak in the house and had to pull up the laminate flooring in kitchen and lounge. In front of the sink, there was a "hatch" that I expected would give access to the floor void, but instead I've found that what I have is chipboard flooring laid onto a DPM (or at least, a sheet of polythene) with approx 20mm battens that have a sheets of polystyrene on top of a concrete floor.

It was a major burst, so there has been a lot of water but the state of the battens suggest to me that it's been wet under there for quite some time. The incoming main doesn't look in great nick so I wonder if it's been steadily wetting the concrete floor. I'm not in a rush to rip up the floor as the kitchen units are on top of it. Does anyone recognise this construction? Is it common? Should I just replace the DPM and board, put some new flooring down and pretend I haven't seen it?

I'm going to pop down tomorrow and core a piece of the living room floor to see if it's the same. It's been purchased to rent out, so I'm keen to keep costs low, but at the same time would rather sort out problems now while it's empty than create a bigger issue further down the road.

Any advice on remedial actions for a floor of this type? Is it likely that the whole floor is like that, or would it be kitchen only? Having lifted the "hatch" I've had another look round the house and there don't seem to be airbricks anywhere, suggesting it will all be concrete?

 

[KenGMac]

Schinklegroover, good evening.

Question? are we discussing a 60s Ex-Local Authority Property? Just a consideration?

What is probable happening is that your house has a concrete slab, over this is a plastic DPM [can be visqueen or Blue thick DPM]

Resting on this plastic are the timber battens and the insulation if it is Polystyrene, it is probably 25,mm thick "Jablight"

As for the Hatch? could be that there has been a leak historically and that was the fix? or someone was careless with water at the sink causing the chip board to rot?? Who knows?

In the event of a leak, what happens is that the escaping water is trapped on top of the plastic DPM and over time, generally a long time the timber battens rot and disintegrate, then the rot starts to cause deterioration of the chip board floor.

As for how far the problem has spread? I have seen the entire ground floor of such constructions being affected, on the other hand I have seen such rot outbreaks confined to relatively small areas, in your case the kitchen the other common area is [obviously] the Bathroom?

It is not easy to define the total area of damage without ripping up loads of areas of the chipboard, not an un-costly venture??

As an aside, this could be an Insurance claim BUT? how long have you owned the property??? If it is a new purchase the Property insurer will decline the claim claiming that the leak was present prior to the Insurance being taken out?

Suggest you try to locate the source of the leak, not easy at times especially if the leak is actually under the chipboard floor, one often missed leak is from the Central heating? do you have a Combi Boiler? if so do you have to top up the system regularly?

If the problem you are encountering is around the sink suggest you have a really careful good look at ALL the pipes under the sink? - HOT - COLD WASTE pipework.

Ken.

 

[Schinklegroover]

Hi Ken,

Not 60s or LA, it's a 1980s semi that was never LA, but seems to have been built as you describe. Having now had a better dig about (online and in the house itself) it looks like the lounge is similar, but it's a floating floor of T&G chipboard. We had a burst pipe in the loft that flooded the house - I'd had a dehumidifier running for a week but the boards in the lounge are starting to buckle so will need to come up. I cored a 60mm hole out this evening and it's the same as the kitchen (polystyrene material under the boards) but the kitchen floor has evidently been replaced more recently as the boards there are modern green chipboard panels, nailed to the battens. Will just have the rip up the lounge floor, dry it out if necessary and replace with similar.

In terms of the leak, the mains supply looks like it's wet, but don't know if that's a source of a long-standing leak, or if it's just been flooded before and the water has sat on the DPM and rotted the battens. When I ripped up the laminate it had a sheet of plastic under the laminate but on top of the floorboards, so any water underneath would have been going nowhere!

 

[endecotp]

the kitchen floor has evidently been replaced more recently as the boards there are modern green chipboard panels, nailed to the battens.

Not necessarily more recently; it's not unreasonable to use the green moisture-resistant boards where there is a risk of water (!!!) in the kitchen and bathroom and regular non-green boards elsewhere - though the more paranoid amongst us fear flooding can happen anywhere. Similarly, it's reasonable to have battens in the kitchen to support the weight of units and appliances but no battens and floating chipboard elsewhere.

The polythene layer you've found may be a "slip" layer so that the boards can expand/contract (thermally) over the insulation without making spookly creaking noises. Or something like that! Certainly the advice from Celotex for making floors of this sort advises a damp-proof layer below the insulation - but only if there isn't one under the concrete - and a "slip" layer above it.

Maybe use something a bit better than white polystyrene when you rebuild it.

This is not an unusual construction.