Floating Floor on Celotex Without Concrete

[tony1851]

Never come across that one before.
One can't imagine a ground-supported slab settling to the point where it tears the dpm.
But if the slab runs onto the inner skin, then surely any settlement of the slab would result in leverage on the wall. So if the residents were not to be slowly killed by radon, they would perhaps be more quickly despatched by collapsing masonry!
Just my humble opinion.

 

[Tangowagon]

This is a very old thread, but I am in a similar position. 1960s bungalow, the old kitchen floor is 60mm screed on 60mm concrete on a sand & gravel base. The only dpm is a thin layer of bitumen paint on top of the concrete. The screed was very damp when the floor covering was removed, but has now dried out over 2 months, I expect it will get damp again if I put any floor covering back down.
The sand & gravel base is visibly damp but will have had 60 years to settle.
My thought is to remove the screed & concrete, blind the base as needed, a once over with a whacker plate then dpm, 100mm celotex, & 22mm floating floor. I see absolutely no point in laying a concrete slab?

 

[Ivor Windybottom]

We have a similar arrangement in a 1950s house. Why do you need to remove the concrete? Just screed and a damp proof coating needed. OK, you won't have any insulation but you will have a dry, smooth rigid floor. Concrete doesn't care if it's damp, in fact it probably helps its strength. Just ensure there's something waterproof between it and the room.

An uninsulated concrete floor would be vastly preferable to a bit of chipboard sitting on just foam and gravel. It will probably bend and sink, as there's nothing rigid.

I think I'm right in saying you'll never get the investment back from pulling up an uninsulated concrete floor to replace it with insulated concrete.

 

[mrrusty]

Not sure I would want it, but the house next door to us has an extension where a floating chip floor sits directly on PIR insulation over DPM and sub base. All signed of by BC. There are also companies making flooring products which are chip over insulation https://foam-tech.squarespace.com/foamtech which is exactly the same construction. As PIR has a compressive strength of about 12 tonnes/sqm I'm sure it's a perfectly OK solution.

 

[Ivor Windybottom]

I'm sitting in my office right now that's a floating floor. 22mm chipboard on top of 100mm of celotex. I thought it would be like a bouncy castle as the whole room is on top of foam but it's as solid as a rock. BUT it has a 6" slab of concrete under the celotex, on top of the compacted stone, DPM etc.

Without the concrete there's nothing rigid. If the ground in one spot decides to settle for whatever reason then there's nothing with any strength to span that hole. It will be absolutely fine on day one and year one. Beyond that who knows.

I'd be amazed if BC would sign this off. If BC would be fine with this then I'm sure every housebuilder in the country would be delighted with not bothering with several grand's worth of poured concrete in each house, they'd all be doing it if this really was an acceptable way of building.

Sometimes people say they have BC approval when in fact they didn't involve them at all and just don't want grassing up by nosey neighbours. I've done so myself!

 

[mrrusty]

No, it definitely had BC sign-off - it was a developer doing a whole house refurb. Nice guy, we drank a lot of brews and put the world to rights, but some of the things he did I wouldn't have done.....I just kept my mouth shut... The house was sold at the end to a young couple, so must have had the cert. for the mortgage.

 

[Tangowagon]

Well, I decided to remove the screed, (it's going to provide hardcore for a driveway)
This is the concrete below, it's a bit thin!
This was a kitchen with a back door, with a very heavy concrete lintel above. When I removed the lintel, I just broke the bricks supporting it & levered it out, allowing it to fall onto the "concrete " floor, where it punched straight through the screed and the concrete.
I'll decide what to replace it with once the skim of concrete is removed.

 

[23vc]

I’d be careful using broken up screed under a driveway, for obvious reasons. Might be ok as a bit of a filler crushed fine but not much else

 

[Nige F]

as an aside Victorian pavers were laid on tamped soil - the joints were left open . Hence the term " sweep it around 'till you lose it " the debris from life just grouted the bricks A M8 of mine reconstructed a floor with membrane and celotex under the bricks . His Mrs. vacuums it - the joints never sealed up .

 

[Ivor Windybottom]

I stack up all my rubble in a corner of the garden until the stack's bigger than a car then hire a mini crusher for the day, turn it all into lovely fine MOT-like stuff. I dry mixed the last lot with cement, compacted it under a patio, it's better than the average airport runway.

I'd rather pay for a crusher and leave it where it is than pay for disposal and new aggregate plus have to lug the stuff up and down the long driveway.

 

[Ivor Windybottom]

That floor looks like complete junk to me. The way that hammer punched through suggests they probably used one bag of cement for the whole room. Get it all out, dig down and do it right, have no issues or worries in the future.