Bizarre UK way of insulating floors

[oh]

Two houses ago, the second catastrophic plastic plumbing push fitting failure (in our brand new build by Britain's favourite builder!) forced us into a hotel while the builder lifted the floor (chipboard) on the ground floor. I was allowed to take a peek and was shocked to see the way that the floor was insulated:

From below, obviously, first the concrete (apparently with plenty of polystyrene embedded). Then, on top, 2.5 cm fibre glass insulation (the one with a paper sheet on one side, presumably to hold it together). Then, ~50mm wooden battens (the ones with rubber strips underneath to compensate for the uneaven concrete), and then the chipboard flooring on top.

Now, the 50mm air gap between the insulation and the chipboard floor was very well ventilated, so what the heck the purpose of the insulation below was supposed to be was lost on me, in my view the floor should have been insulated the way we do in Scandinavia, with the insulation material in direct contact with the flooring, and with the air space

*below*. Anyway the site manager told me that this was the standard way they insulate the ground floor so I just shook my head and let them get on with it.

So now I'm in a third-floor flat by another builder, built around 2000, and lo and behold what do I see when I cut open the chipboard floor to move a radiator, exactly the same way of putting down the insulation. No wonder the bloody floor is cold on your feet in the winter, through the hole I can feel the draught and the insulation below the air gap would be completely useless!

So, what possesses at least two British builders to lay floor insulation in a way that is totally ineffective? Is this really according to Building Standards?

[sm_jamieson]

No responses yet - I guess nobody has seen this ? How did you know it was paper-backed fibreglass without seeing both sides of it ? Was the void ventilated to outside ? The rubber covered joists were on top of the fibreglass ? Or was it just between the joists ? If you description is correct, it seems rather odd. Who was the builder ?

This is not a ground floor, I would be surprised if the void was open to outside ventilation.

This all depends on whether the void was vented to outside or not. Quite usual to batten concrete and boards on top.

Simon.

[Hugo Nebula]

On Sat, 22 Mar 2008 22:53:10 +0000, a particular chimpanzee, oh randomly hit the keyboard and produced:

This isn't a normal flooring make-up. A concrete ground bearing slab generally has a membrane and insulation underneath. When the client wants a timber floor on top, one can place battens and boards over to give the appearance of a timber floor, but it performs no other function than being decorative. It shouldn't be ventilated, as it's on the warm side of any insulation. In your case, I don't know why there is additional insulation there.

There shouldn't be any deliberate ventilation between the joists in a third-floor flat. And there should be substantially more than a bit of insulation between the joists in a floor separating dwellings.

The housebuilding sector has the right to choose its inspectors, rather like a burglar would have the right to choose who arrests him. Hardened criminals, such as Barratts and Persimmons, frequently pick the most lenient.

I suspect not, but as the NHBC is in the pocket of the major housebuilders, who's going to say otherwise?