Kieran Bradley is director of architecture at consultancy Pick Everard
As a society, much is made of our ability to repurpose where possible. Buildings are no different, and in recent years we’ve come a long way in making our construction choices more net-zero ambitious. Now, Labour is pledging to build 1.5 million homes by the end of the current parliament, with redevelopment a core theme of its plan.
“It is important to consider how exactly the office-conversion plan will be achieved, given the clock is ticking”
Britain has historically built fewer homes than its European peers, and today, on that measure, it has a shortfall of 4.3 million dwellings. Big firms are steadfast in their commitment to make use of derelict or unused spaces here. This is evidenced by John Lewis’ plan to build 10,000 rental homes above Waitrose stores, with one such development in Bromley recently gaining planning permission.
With the amount of vacant UK office space standing at its highest level since 2014, totalling 102 million square feet, it is clear that reuse of this stock remains up for examination.
Conversion challenges
In practice, perhaps the biggest difficulty is the most obvious one: structural conversion. A traditional office, while sharing some interior similarities, will have its own unique structure compared to a residential home or apartment block. Offices will generally be built in steel frames, as this process is quicker and more cost-efficient for developers.
Residential homes, on the other hand, are typically built with concrete frames due to their acoustic-insulation and fire-resistant qualities.
These two factors traditionally make concrete a much safer choice for residential developers, who must meet strict safety regulations to satisfy occupancy detailing, particularly in high-rise buildings.
This extends to the complex issue of a building’s facade, with some cladding systems used on office high-rises currently undergoing costly remediation work, as part of government building-safety action post-Grenfell. During the conversion process, any existing cladding should undergo a thorough survey to identify potential complications.
From a mechanical and electrical (M&E) perspective, typically, under an office build, and depending on how big the floor plate is, one system will be used to service the entire building. In contrast, each apartment may need its own M&E system, placing cost challenges at the forefront of developers’ minds.
Heating, lighting and plumbing are also set up to cater for much larger numbers of people than would be present in a family home or block of flats, so would likely need completely stripping out of an office and starting from scratch.
Structurally, further complications may also arise depending on the size of the floor plates. In an older building, the floor plates might be deep, meaning the build might need to account for the addition of lightwells into the structure to increase natural light visibility.
Adding or amending staircases, lifts for apartments or service risers, for example, essentially means chipping away at the structural integrity of a building, which could lead to increased costs.
Above all, developers must understand the whole lifecycle of embodied carbon that is emitted during this process. While ‘end of life’ is typically the best time for an office conversion, just exactly how viable this is from a cost perspective, or permissible with a net-zero hat on, must be at the forefront of minds pre-construction.
Societal shifts
There are also likely to be questions about who these new homes are for. John Lewis’ plan is very much limited to city centre areas, which are likely to have a higher number of individual occupants and middle-aged couples.
We must applaud new ways of living and working to meet shortfalls, including radical concepts like ‘15-minute cities’, but just how far these plans will go to appeal to families, particularly with how densely populated London is, remains to be seen.
It is important to consider how exactly the office-conversion plan will be achieved, given the noted challenges, and the countdown clock is ticking.
Perhaps, then, it is up to those across construction, including architects, contractors and engineers, to collaborate more closely on ambitious redevelopment initiatives, to ensure innovation becomes an enabler to a much cleaner net-zero future.
