Rebuild or retrofit

The big question...

In the context of the Climate Emergency declared by Cambridge City Council in February 2019, Cambridge Architecture asks whether the Park Street Car Park site is a prime candidate for leading by example with repair, retrofit and responsible reuse

WORDS THE SECRET ARCHITECT / ILLUSTRATIONS ANDREW DRUMMOND

Park Street Car Park is scheduled for demolition. Its replacement will re-provide a reduced provision of car parking (-165 spaces), an increased provision of cycle parking (+70 spaces), a 200-bed Aparthotel, and a bee hotel.

The £90m new build will take four years to complete – the car park will open after two years followed by the above-ground hotel.

The existing four- to five-storey concrete frame contains about 3,245m3 of reinforced concrete.

Filling 750 30-tonne tipper trucks, generating 1,500 more vehicle movements through the city.

The new frame requiring 775 fully loaded 8m³ concrete trucks arriving on site, generating 1,550 vehicle movements.

The existing structure offers 390 car spaces and 200 cycle spaces, public toilets and a small retail unit.

The upper parking deck could offer a secure working space with low rent space for makers, craftspeople, artists and start-ups. An estimated 300 30-tonne tipper trucks will be filled, generating 600 vehicle movements through the city’s historic core.

If the demolished waste and spoil from excavation were combined, the resulting ‘hill’ could rival Castle Mound.

So, in some ways we’re back to the start with a concrete frame ready for fit-out, and another year of work to turn it into an Aparthotel.

Reduce car parking and increase cycle spaces, erect prefabricated workspace on upper decks and crane 20-30 housing units on roof.

It could offer a more sustainable transport hub, affordable workspace and up to 1,500m² of affordable small-unit housing. When the existing frame is removed, the digging can start. A 10m-deep hole across the site will need to be excavated.

After three years, a new framework would be in place including 6,205m³ reinforced concrete. This equates to about 1,800 tonnes CO2.

Could we just inhabit the existing frame? What could it offer?

The views from the rooftop car park deck become the views from people’s homes.

So, rebuild or retrofit? Low-carbon conversion or investment in new build to create capital for larger family housing?