Demolish or adapt?

When should the new replace the old?
17 March 2020

Interview with 

Hannah Baker, University of Cambridge


A skyscraper under construction with cranes on the roof


What if the greenest building is the one that is already built? Melanie Jans-Singh went down to the Flying Pig pub in Cambridge and spoke with Hannah Baker, to find out more about when to demolish buildings or leave them standing...

Mel - The Flying Pig is the Naked Scientists' old local pub and has been a live music venue for decades. Over the time, there's been some famous people here too, Syd Barrett is said to have met the future pink Floyd member David Gilmore here in the 50s. However, the pub was under public consultation to be demolished last summer. To find out why, I met with Hannah Baker, a researcher at Cambridge University, who studies how the decisions to demolish or adapt buildings are made, and I met her outside The Flying Pig.

Hannah - So it was being considered in terms of demolition because for the whole site they want to provide new offices. They were also, I think, at some point considering housing, and one of the key issues is that if you demolish a building you can provide much larger floor areas. And the developers were saying that although they recognised it had been a live music venue, that use could maybe be put inside a different building, but then because of the reaction of the community they've kept it. And one of my favourite quotes is that this whole idea of heritage being soaked into the walls, the music, and when we go inside, you'll see that there's posters covering absolutely everywhere reflecting this.

Mel - We found a quiet table inside to discuss what is the process of deciding whether to demolish or adapt a building.

Hannah - So initially you would do a number of different assessments of the building. So a key one in terms of heritage is the heritage impact assessment. It looks at its significance and different values attached to that: is it architecturally significant, historically significant, socially significant? Has it got a listing? So is it protected by planning policy? And then you also do, particularly for larger urban regeneration sites, environmental impact assessments.

Mel - So who are the people who do this? Is it the architects or the people who live there and decided they wanted to develop their building?

Hannah - So there was a huge number of stakeholders - people who are affected by the decision. So there's a difference between stakeholders and decision makers. So your decision makers here are going to be mainly your developers and your planners within the local authority. Often your landowners and your developers are the ones that are going to be investing in the site, spending the money to regenerate it, and then obviously they will make the profits from that. But because of the planning system that we have here in the UK, you do need to get planning permission to be able to do that. And at the same time behind the developers, you've got a huge number of people as part of the design team, and so they're the people who calculate whether it will be better to demolish or adapt.

Mel - And so what metric do they use and on what basis do you make that decision?

Hannah - It often comes down to economic viability. They will look at the physical attributes of a building and whether it can be made fit for purpose. So often a building will be demolished, it it's become obsolete so it can't be used anymore. And they will look at things like the floor to ceiling heights, whether or not you can fit in updated services, look at the structure wall arrangement, and that can all determine the costs of intervention.

Mel - It's not just the cost though. When considering the environmental impact of a building, it's a trade-off between the embodied emissions, from the building process and its materials. But new builds could also be more energy efficient to operate. However, a recent study has found that a third of the emissions from office buildings are from these embodied emissions. Architects are therefore campaigning that the "greenest building is the one that already exists" because it's also important to keep that local heritage in the area that people want.

Hannah - So one of the things about where we are at the moment is it is a large urban development site. So we've got The Flying Pig and that seems to be a fairly easy decision now that it will be kept, because of that community campaign to save it and those connections to heritage. But what I actually find interesting is that we also have some big office blocks behind us and to the right of us. And from the looks of it, they're going to be demolished, because they don't have this whole heritage value attached. And if you look at some of the consultation presentations which developers have put out, they do talk about how they're going to consider embodied carbon. But it'd be interesting to see if they actually do a comparison between retaining those buildings, which are already here against the demolishing and new build, or whether it's just they're trying to reduce the material in the new builds. But then when we go back to that embodied carbon argument, potentially, maybe you should keep everything and then decide what goes.


I know it’s fashionable in the scientific community, but must you start every sentence with “So”?

...but it bugs the hell out of me!

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