Commercial to Residential Conversion: A Guide on How It Works

That empty office floor in London is not sitting still. It is quietly costing you money. Business rates, service charges, insurance and security keep draining the account while the space stays dark and the market next door asks for homes, not desks. Most owners assume turning a commercial building into flats means a long, uncertain planning fight.

Often it does not. Recent changes to permitted development rules have created new opportunities for many commercial-to-residential conversions, but many property owners are still unaware of how these changes may affect their projects.

A commercial to residential conversion changes a building's legal use from business to housing and rebuilds the inside to match. Done well, it takes a low-yield or vacant asset and turns it into flats that sell or let at London residential values. Craftex handles this end to end, from the first feasibility check through to handover, as a single commercial to residential conversion service.

This guide covers how the process works, where projects stall, and how to tell early whether your building is worth converting.

Many commercial-to-residential conversions face challenges before construction begins because the wrong building was selected or the project was not assessed properly.

Commercial to residential conversion is the process of taking a building used for business, such as an office, shop, gym or former clinic, and turning it into one or more homes. It covers two separate things at once: the change of planning use, and the physical build that makes the space fit to live in.

The planning side matters more than most people expect. Since 2021, a permitted development right called Class MA has let many Class E commercial buildings switch to residential use through a lighter prior approval process instead of a full planning application. In March 2024 the government scrapped the old 1,500 square metre size cap and the three-month vacancy rule. A far wider pool of buildings now qualifies, including larger and still-occupied ones.

That does not make it automatic. Prior approval still tests specific things, and in London the bigger risk is local. Many boroughs have used Article 4 directions to switch Class MA off in town centres and employment areas, which pushes you back to full planning. Check that first, before anything else.

Every conversion we take on runs through the same five stages. We call it the SHIFT Framework: Suitability, Headroom, Infrastructure, Fit, and Testing. Each stage answers one question, and each one can quietly kill or save the project.

S - Suitability: is this building a real candidate?

Suitability is the honest first look at whether the numbers and the fabric stack up. This is where most commercial property conversion projects are won or lost, long before a single wall moves.

We look at floor plate depth, ceiling heights, the position of windows, and how much daylight can reach the middle of the building. A deep office with a dark core is far harder to turn into decent flats than a narrow period building with windows on both sides. We also model the sale value against the buy-in price and the build cost. If the finished flats will not clear the total spend with margin, the answer is no, and hearing that early saves you six figures.

The most common mistake we see is buyers choosing a property without first considering whether it is suitable for residential living.

H - Headroom: what is your planning route?

Headroom is your permission to convert, and it sets your timeline and your risk. You have two routes: Class MA prior approval, or a full planning application.

Class MA is faster and more certain. The council can only assess a defined list, including transport, contamination, flood risk, noise and natural light, rather than the full weight of planning policy. A decision usually lands within 56 days. Full planning is slower and more open to refusal, but you need it for anything beyond a change of use: extra floors, extensions, external changes, or a mixed-use scheme. Our property redevelopment and repurposing team maps the right route before you commit capital.

Here is what trips people up. Class MA is a change-of-use right only. The moment your scheme needs new windows cut into a blank wall or an added storey, you are into full planning, and the permitted development shortcut disappears.

I - Infrastructure: can the bones take it?

Infrastructure is the structural and services reality behind the design. A commercial building was engineered for open floors, heavy footfall and machinery, not for private homes with kitchens, bathrooms and quiet bedrooms.

This stage covers the frame, drainage, acoustics, insulation, fire strategy and the full mechanical and electrical layout. Homes need soil pipes routed to every bathroom, sound separation between flats, and thermal performance that meets current building regulations. Offices rarely have any of this in the right place. On most conversions we run, the services rethink, not the finishes, is where the real budget goes. Underprice this and the whole job unravels.

F - Fit: designing and building for living

Fit is where the building becomes a home rather than a chopped-up office. Layout, light, storage and flow decide whether flats feel worth their asking price or feel like a compromise.

Good conversion design places habitable rooms where the daylight falls, hides the servicing cleverly, and gives each unit a sensible run from the front door to living space. This is design work, not decoration, and it is why we bring in at the layout stage rather than after. A clever plan lifts the value of every flat in the block. A lazy one leaves money on the table on every single sale.

T - Testing: sign-off, safety and handover

Testing is the stage that makes the homes legal, safe and sellable. Planning permission and building regulations are two separate approvals, and passing one does not pass the other.

Building control signs off structure, fire safety, insulation, ventilation and electrical safety. On larger blocks the fire strategy carries real weight, especially in buildings above 18 metres. You also want the warranties and certificates that mortgage lenders and buyers will ask for. Skip the paperwork and your finished flats become hard to sell, which is a slow and expensive way to lose the margin you worked for.

Costs vary widely, but a fairly clean London office-to-flats conversion often runs from around £1,200 to £2,000-plus per square metre for the build, before professional fees, finance and planning. The spread depends almost entirely on the Infrastructure stage and how much structural and services work the building forces on you.

The return case is simpler. Commercial yields on tired London stock are thin, while residential values per square foot are usually far higher. That gap is the whole reason the conversion market exists.

An empty commercial building is a cost that grows every month you leave it. The March 2024 rule changes opened a genuine window, but Article 4 directions across London are steadily closing it in the areas with the strongest demand.

If you own a London commercial building and want a straight answer on whether it stacks up, talk to the Craftex team. We run the Suitability and Headroom checks first, tell you honestly if the numbers do not work, and take on only the projects that will actually make you money.