'Expanding' polystyrene

[Andrew]

Lots of photos in yesterdays papers about the burst 32 inch water main in London and the effect on an underground carpark.

For those who didn't see it (or hear the Jermey Vine phone-in), this was reported as 'polystyrene expanded after being submerged by a massive flood). I think not !!!. Do people not know about buoyancy these days ?, or the reason why massive metal ships don't sink ?.

The upwards force of the water was sufficient to lift the carpark floor and the vehicles parked thereon, jamming them into the ceiling. There seemed to be an awful lot of EPS under that floor. It cannot have been there as a thermal insulation (car park), so maybe there was a problem with the soil. Or maybe the builder had a load of EPS left over and wanted to avoid disposal fees. May be the builder bought the EPS and was told by building control that it was the wrong stuff - get rid of it ?.

There used to be a website hosted by TML the chunnel builders, and how they built the Sangatte side. Essentially this is a massive concrete-lined hole, presumably below the water table, and to stop it popping back up, something like 160,000 tons of concrete were poured to cover it.

[spuorgelgoog]

The Guardian don't:

polystyrene insulation under the car park floor in south-east London appear ed to swell ... Upset woman said "we were told we cannot move it because there is a po ssibility with the pressure of the car there could be a blast because of th e gas inside, or something. It can blow up the whole building. "The problem is who to contact. Someone has said the car insurance mig ht not cover it because it didn?t happen from the driver him or her self. We are in really, really bad shape.?

Good thing she didn't have to cope with the Blitz or she might have streake d her mascara.

The Independent are a bit confused too:

floodwaters raise polystyrene floor of car park

when insulation for an underground car park absorbed flood water and became swollen

But the Indy's commenters appear to understand more than the journalists

Owain

[Brian Gaff]

I did wonder why it was there as well, and so did a number of the people interviewed who lost their cars from what I heard on the radio. I suspect somebody is going to be liable for a large amount of dosh for this, for whether it expanded or floated, neither should have been possible in such a building. It does make one wonder what the rest of the building is like for construction and stability. Brian

[Chris Hogg]

It's a measure of the technical competence of media reporters: they haven't any; they're technically illiterate!

The large storage tanks used for holding fuel at petrol stations can also rise up out of the ground, i.e. float, if the area gets flooded and the soil saturated.

But I expect it was tiny when dry and just swelled up! :-))

[Andy Burns]

Big hole to fill? Concrete £100/cubic metre, EPS £15/cubic metre ...

[Jethro_uk]

So can LPG tanks, which have to be mounted on a concrete base to prevent such mishaps

[Tim Lamb]

Trenches in clay would be sided with foam to allow for movement. Don't know about oversite concrete as block and beam are preferred for domestic situations.

[newshound]

That was my thought too. Supporting a concrete floor with negligible tie-in to the walls? One hopes the walls were built on proper foundations!

[Dave Plowman (News)]

It would be unreasonable to expect any reporter to be an expert on all things technical. So most are merely reporting what they've been told - or have to make it up if they can't find a true expert. A better one might question something he finds unexplainable - but as you say not all are going to have any technical knowledge at all.

But it simply backs up what I've said for ages. Because you've read or heard something in the meja doesn't make it accurate. If only so many on here who quote newspaper articles to back up their bigoted views would understand this.

[Huge]

If you've ever driven up the A1(M) through Hatfield, the walls of the tunnel under the shopping centre are full of expanded polystyrene. I watched it being built.

[Andy Burns]

Don't know if everyone's been looking at similar pics, but looks like 2" of screed on top of at least 3' of polystyrene, assuming those two floors were level beforehand ...

[Malcolm Race]

Pilars for concrete bridges are often built with concrete poured around an EP core

Malcolm

[Tim Watts]

Thanks for a very clear picture.

That hasn't expanded (stupid journalism).

I reckon it's either floated (assuming there's a lot more underneath) or the water leak was under it and it's acted like a ginormous piston.

[T i m]

Yeahbut are there really people out there [1] that don't know that expanded polystyrene floats (and very well, as I suspect most here found out as kids?). I only saw a glimpse of it on the TV news when it first happened and I then explained to the Mrs *what* had happened (that the concrete car-park floor floated up on the polystyrene and crushed the cars against the roof). What I didn't know was why so much EPS was there in the first place but I guessed it might be something to do with a large unwanted void that needed filling cheaply? No wonder 'the world' is such a complete mystery to many of them. ;-(

Or you simply don't believe it in the first place (because it simply doesn't make sense), like the whole 'it expanded' thing.

I wonder if the same people watched that Grand Designs recently where they built a *house* beside a river but built it on a large 'float' so it would rise up if there was any flooding?

Quite. ;-(

Cheers, T i m

[1] I know there are but ... ;-(

[GB]

It's strange that the EPS is so strong. There's a fair bit of weight on top, but the EPS doesn't appear to have deformed, even where the wheels of the car are. The surface on top may be spreading the load, ofc, and the side with the range rover seems a bit lower than under the smaller cars.

Still, I'm used to the EPS used for packaging, and builders' EPS may be proper 'ard stuff. :)

[whisky-dave]

Yes I know EPS floats but I didn;t know carparks used it for hardcore. There'll be plenty of samsung galaxy 5s availabe for hardcore too soon :-)

[T i m]

No, nor did specifically I but I knew it was used for underfloor insulation so also knew it was capable of supporting some fairly heavy loads (like under kitchens etc). ;-)

Cheers, T i m

[newshound]

The actual floor will be a concrete screed with a rebar mesh, that spreads the load. The EPS doesn't have to be all that strong, if you work out the average floor loading.

[pamela]

It may be cheaper but I wonder if it meets requirements for the insurance to be valid?

[Chris Hogg]

It's also used under roads, IIRC in places where there are long cold winters IIRC, see

Maybe it insulates the sub-base from the road getting warm when the black-top absorbs heat from sunshine. Or maybe it keeps the road surface from freezing. Or maybe it just accommodates distortions due to frost heave, so keeping the road surface intact. IOW I haven't a clue why it's used! :-)