Car Park of Death!

Via Tim I discovered the Observer’s architect critic has joined the chorus demanding the horror of Preston Bus Station be saved. The main argument appears to be that it ” it embodies the spirit of its 1960s age”, you can argue if that is a good or bad thing visually but in the world of civil engineering, particularly those parts related to large concrete car park type structures, that is reason enough to flatten it. Indeed the man himself admits the reason before attempting to dismiss it;

“The bus station is not alone. It is part of a company of buildings from the 1960s and 70s that fall victim to a vicious compound of circumstances. They are tough, not obviously charming and carry a label no PR expert would have chosen, of “brutalism”. Some have serious technical problems, albeit often exaggerated. Some have serious technical problems, albeit often exaggerated

I will now demonstrate why those serious technical problems have not been exaggerated. We begin in the 1960s when reinforced concrete was a new idea and building huge civic structures in the brutalist style was all the rage. After the architect had produced his swooping lines and grand gestures for the new Preston depot he handed it over to the designers to do the actual hard part of making it work and not fall down, and here is were things went a bit wrong. To be blunt the concrete specifications of the time allowed fairly weak, porous concrete and didn’t require much cover to the reinforcing steel, for those interested in water/cement ratios and porosity of concrete I commend you to this handy government guidance. To add to the fun the design codes of the time were also a bit ‘optimistic’ on concrete strength in shear so most designs weren’t really strong enough and didn’t have the safety margins the designers assumed.

So fast forward a few decades to the 1990s and these chickens begin to roost, car parks start rotting far faster than planned and a few demolition contractors get nasty surprises when the buildings fall apart faster than expected. The big change is probably Pipers Row car park, the top floors of which quite dramatically collapse overnight;

Pipers Row Car Park, pride of Wolverhampton. It got it's own HSE report you know, where do you think I nicked the photo from?

After the HSE investigation a whole generation of material engineers relax knowing their careers will be safe for life, looking after corroding 1960s/70s car parks will be a job for life for anyone who cares to do so. While the collapses generally get avoided these days that doesn’t mean the buildings are OK, it just means they get demolished earlier than expected leaving the owners to try and explain the problem to confused punters looking to park. A good one was Heathrow Terminal 3 car park;

Once a car park stood here, not anymore obviously.

You may be forgiven for thinking this was just part of the ongoing 'permanent rebuild' strategy for Heathrow Airport. However this is the old T3 car park, the one that was conveniently opposite the terminal till it was condemned by a mate of mine due to massive corrosion. So this car park was demolished and a new one built further away. If you've ever been at T3 and wondered why the car park is so far away and why the pick-up/drop off area is so huge, that's why.

This is still a live problem, a quick google throws up a car park in Nottingham that got the old ’emergency closure’ treatment a couple of years back and only last month a Southend car park collapsed during demolition, the top five stories letting go as they had corroded far worse than previously thought. It should now be obvious why Preston Bus Depot has to go, it’s not going to last long in any event so better to take it out while it’s safe before it decides to do the job itself.

I will leave the final word for today to another article in the Guardian, quoting a former Secretary of State for culture when the first listing of the depot was rejected;

“It therefore appears to the secretary of state that the main attractive feature of the design was the result of a miscalculation which led to a poor quality of construction.”

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