Every few years the same proposal returns with fresh urgency: the city has empty offices and a housing shortage, so why not turn one into the other? The logic is appealing. The buildings exist, the structure and the embodied carbon are already paid for, the sites are usually well connected. In practice, office to residential conversion ranges from some of the best homes in London to some of the worst, and the difference comes down to a handful of physical facts about the building and a few rules about what the conversion has to deliver.
The rules in England
Converting an office into flats has two routes through the planning system. The first is an ordinary planning application, which gives the council full control over the design, the mix of homes, affordable housing and everything else. The second is permitted development, which allows a change of use without a full application, subject to a narrower “prior approval” process.
Permitted development for offices to homes was introduced in England in 2013. Today the relevant right, known as Class MA, covers a broad range of commercial, business and service uses. Under the current rules the building must have been in one of those uses for a continuous period of at least two years before the application, and listed buildings are excluded. The council cannot refuse on general design grounds, but it does assess a defined list of matters, including:
- transport impacts and safe access to the site;
- contamination and flooding risks;
- noise from nearby commercial premises;
- adequate natural light in all habitable rooms;
- in conservation areas, the effect of changes to the ground floor;
- fire safety, for taller buildings.
The rules were tightened after years of criticism. Since 6 April 2021, homes created through permitted development must meet the nationally described space standard, and none can have a gross internal floor area of less than 37 square metres. Before that, there was no minimum, and some conversions produced flats smaller than a hotel room.
Why the early conversions gave the idea a bad name
The first years of the right produced some notorious schemes: former office blocks on business parks and ring roads turned into hundreds of tiny single-aspect flats, some without windows that opened onto anything but a car park, some far from shops, schools or doctors. Government-commissioned research into the quality of homes delivered through permitted development found that they were much less likely than homes approved through full applications to meet space standards or to have adequate access to light and amenity space.
The problems were not inherent to conversion. They came from converting the wrong buildings, in the wrong places, with no requirement to meet basic standards. The same office stock converted through a full planning application, with a council able to insist on proper flats, tended to produce far better results.
The physics of a good conversion
Offices and homes want different things from a building, and some offices can bridge the gap far more easily than others.
Floor plate depth
Modern offices are deep. A large open floor with the lifts and stairs in the centre suits desks and artificial light. Homes need daylight in every habitable room, and daylight fades quickly with distance from the window. A deep plan converted into flats leaves the back of each unit dark, or forces long corridors lined with single-aspect units, the exact configuration that performs worst on daylight, as discussed in our piece on density and daylight. Narrow, older office buildings, often from the early twentieth century, convert much better.
Windows
Sealed glass curtain walls were designed for air-conditioned offices. Homes need opening windows for ventilation and to avoid overheating, and replacing or adapting a facade is one of the largest costs of conversion. Buildings with punched windows in a masonry facade are far easier.
Plumbing and servicing
An office has toilets clustered around the core. Flats need kitchens and bathrooms in every unit, which means new drainage runs across the whole floor, and drainage needs a fall. Floor to floor heights in older offices can be generous enough to accommodate this; in others the soil pipes eat into ceiling heights and determine where every flat’s bathroom can go.
Fire safety and access
Residential buildings are held to different fire standards from offices, and taller buildings now require more robust stair provision. An office core designed for daytime occupancy by people who will be awake may need significant changes before people can sleep in the building.
Location still decides most of it
A building in a town centre, close to transport, shops and schools, becomes a normal part of a neighbourhood when it turns residential. The same building on an isolated business park becomes a cluster of homes with nothing around them, and no amount of internal design can fix that. The best conversions are usually on high streets and in town centres, where new residents bring evening activity to streets that used to empty at six, and support the shops below.
What works
- Narrower, older buildings with punched windows and modest floor depths.
- Central locations with everyday services within walking distance.
- A mix of flat sizes, including some family homes where the building allows, rather than wall-to-wall studios.
- Using the deep parts of the plan for the right things: storage, bathrooms, circulation, cycle stores and shared spaces, keeping the perimeter for living rooms and bedrooms.
- Keeping the ground floor active, with a shop, café or workspace on the street rather than a blank residential lobby.
- Planning ahead for the flats as homes, with private or shared outdoor space where the building can provide it: roofs, balconies within the structure, courtyards.
The honest assessment
Office conversions will not solve London’s housing shortage. The stock that converts well is limited, and much of the most vacant space is in exactly the deep, sealed buildings that convert worst. But done in the right buildings, with the right standards, conversion retains structures that would otherwise be demolished, adds homes in places with excellent transport and brings life back to streets that lost it. That is a good outcome, as long as the quality rules stay firmly in place.
