Homes from offices

Plans for office-to-residential conversions are being presented as a panacea for many ills, but how would it really work?

The proposed relaxation of development rights, due to be implemented this spring, will allow an automatic change in Use Class from B1(a) office to C3 residential in a move intended to address the twin problems of widespread unoccupied office buildings in towns and the housing shortage. 
The government hopes this planning shortcut will give construction a shot in the arm and help boost regional economies, while developers stand to profit as residential space is generally worth a great deal more than office. 

However, local councils are seeking exemption from communities secretary Eric Pickles’ policy, fearing that an unco-ordinated building boom could flood parts of the market with sub-standard properties and perhaps create long-term problems for commercial districts. As a result, some of the UK’s largest cities and most of the London boroughs have applied for exemption. Now planning experts are warning that ministers may be forced to delay implementation or face legal challenges.

Whatever form the planning policy eventually takes, architects targeting such schemes need to prepare themselves for the many logistical and technical design challenges involved. While some office buildings will already offer generous heights and daylight levels, others will need intelligent re-inventions of deep-plan offices, incorporating courtyards, light wells and other spaces not seen in most standard new-build housing. 
Externally, large office windows and balconies may fall well below the thermal requirements of Part L 1B and the aesthetic needs of potential tenants, making a re-clad the only option. Meanwhile, issues related to sound transmission, privacy, fire protection, increased drainage and other services, outside amenity space and parking provision, may also affect designs.

As a result, some offices will struggle with a change in use but others will flourish, says Stephen Marshall, architect director at Building Design Partnership (BDP), who designed Witham Wharf, the conversion of a 1970s concrete-framed office block in Lincoln: ‘The office-to-resi market has so far largely focused on period buildings, but I’m always surprised that there weren’t more conversions of concrete office blocks built in the 1960s and 1970s. There’s a surfeit of this type of stock, much of it empty and under local authority ownership, and the 3m floor-to-floor heights, great views and relatively open concrete structural frame make it perfectly suited to residential,’ he says.

There is an obvious logic to converting office space to residential, especially outside London, where offices are in over-supply. Many councils have gone through a consolidation of their services, leaving significant amounts of city office space lying dormant and un-lettable in this economic climate. Communities and Local Government figures suggest that relaxing the rules could potentially create 22,000 (net additional) new homes.
Frustratingly, however, developers may be most interested in investing in the capital, where house prices are performing best. Without a national house pricing rebound the policy may fall flat. 

 

Lincoln’s 1970s Witham Wharf office block before conversion.
Lincoln’s 1970s Witham Wharf office block before conversion.
Witham Wharf after BDP’s residential conversion.
Witham Wharf after BDP’s residential conversion.

Still stuck with planning 

Although it is intended to simplify the planning process and help bring schemes to site faster, the proposed deregulation only applies to the Use Class of a building and will not allow design teams to circumvent other time-consuming aspects of planning. For example, material changes to the building facade will still have to be submitted for assessment and listed buildings still need consent. 

‘It takes things back into the realm of the planning authority, which to some extent defeats the whole object of speeding up development,’ says Roger Zogolovich, developer and architect at Solid Space. ‘As a result, this is unlikely to lead to a wholesale transformation of our towns and cities with every empty office suddenly becoming a block of flats.’ 

Still, architects will relish the opportunity to breathe new life into buildings that have outgrown their roles and create more diverse urban environments that cross the conventional boundary between live and work spaces that Use Class orders impose.

‘London and other UK cities are increasingly controlled by the over-enthusiastic implementation of planning policy, which stifles evolution of the city and prevents densification of use,’ says Philip Turner, associate director at architect Allford Hall Monaghan Morris (AHMM). ‘This new approach could open the door for housing with a greater density of residential footprint, subverting the utopian BRE guidance on minimum overlooking distances, daylight factors etc.’

Turner points to a new typology of housing created from low and medium-rise groundscrapers, whose deep floor plates will require the insertion of courtyards to bring light and ventilation into the plan. ‘This type of housing, designed around an internalised aspect, is quite common in the Middle and Far East and more akin to modernist schemes of the 1960s and 1970s and some of Ralph Erskine’s work, than what volume house builders have been producing lately,’ he says.

Carving courtyard spaces from existing floor plates can require major modifications to the building frame, as could the inclusion of extra services and drainage for bathrooms and kitchens, perhaps dropping extra service risers through floors, or in the case of offices with tall floor to ceiling heights, gathering services under raised floors or false ceilings. And new stair cores may needed.

‘In many cases you’re not going to know exactly what’s inside the structure until you start work on site,’ says BDP’s Marshall. ‘Our initial survey at Witham Wharf failed to reveal that some of the floor plates were different sizes, which held things up and added to our risk profile. The biggest alterations were needed at ground floor level, taking drainage connections outside the building perimeter meant a lot of work breaking out the slab.’

A change of use from office to resi will certainly affect Building Regulations, specifically sections on structure (Part A), fire safety (Part B), and conservation of fuel and power (Part L). A building that falls under Section 20 of the London Building Act may also require extra fire safety measures.

Increased thermal performance requirements will often require an upgrade to the facade using an over-clad or re-clad solution, which has the added advantage of increasing the building’s lifespan and improving its appearance for potential buyers.

At Witham Wharf, BDP found the existing exposed concrete facade could be easily dismantled to enable a complete re-clad with a high-performance system. But windows in period buildings will almost certainly need upgrading, which could prove a challenge if it is listed.

Replacing mechanical with natural ventilation will be a common path for conversions to allow tenants to open windows, making more recent office blocks appealing to architects, says AHMM’s Turner: ‘The office and housing sectors are already converging somewhat in environmental terms. Office owners and tenants today often want mixed-mode ventilation, a better quality of construction and reduced energy use with hyper insulation, high performance double glazing, clean plant.

Berkeley Homes’ Rowan House. City of London, exterior visualisation.
Berkeley Homes’ Rowan House. City of London, exterior visualisation.

There may be a dearth of housing, but who is to say that in 10 years the same will not apply to offices, necessitating another round of refurbishment or replacement?

Cost benefits

Where clients have the will even Passivhaus levels of energy efficiency can be achieved on a conversion, adds Marie-Louise Dunk, director at Aberdeenshire-based refurb specialist JamStudio: ‘A number of practices have been working with the Scottish Passivhaus Centre and Scottish housing associations to refurbish empty offices to Passivhaus standards, and provide amazing quality accommodation that is cheap to run. Cost-wise this is more achievable than previously appreciated: some HAs have spent £30,000-40,000 per flat and expect to recoupe their costs in just over 10 years.’

Although the changes are almost certain to go ahead, many councils feel a switch to residential will create a long term change to the character of business centres, potentially reducing employment levels. And the government’s lack of clarity over developer liability for Section 106 payments or affordable housing provision could affect revenue. A spokesman for Croydon Council told PIP: ‘The office market remains strong with new development, refurbishment and transactions. Clearly the contemplated permitted development rights will undermine this economic activity.’  Leeds and Manchester city councils voiced similar concerns.

But perhaps the real problem is inflexibility in building design. Today there may be a dearth of housing, but who is to say that in 10 years the same will not apply to offices, necessitating another round of refurbishment or demolition and replacement? ‘The renewal cycle of buildings is speeding up at time when it should be slowing down,’ says AHMM’s Turner. ‘The development of a building type that can adapt over time rather than requiring total re-working could ultimately render the idea of Use Classes and separate Building Regulations obsolete,’ he concludes. ‘We already build schools like offices and healthcare like housing. Perhaps we need a Universal Use Class for all new buildings.’