Office to residential: what Class MA permitted development allows

When an office building stops letting, turning it into flats is usually one of the first ideas on the table. The planning shortcut tends to get discussed first and the building itself last. I'd argue it should be the other way round, because the building is what decides whether the scheme works.

This is a builder's overview, not planning or legal advice. Class MA has been amended since it was introduced, so read the current rules on GOV.UK or the Planning Portal, and speak to your council or a planning consultant before you buy or commit.

What Class MA is

Class MA is a permitted development right in England. It allows a building in Class E use, the commercial, business and service class that includes offices, to change to residential use without a full planning application. Instead, you apply to the council for prior approval.

It comes with conditions. Some relate to the building's recent use, and some buildings and locations are excluded altogether, including listed buildings. Councils can also remove the right in parts of their area with an Article 4 direction. Check all of these for your building before you count on the route.

It's also worth being clear about what Class MA covers. It's a right to change the use. Changes to the outside of the building, such as new windows, balconies or extra floors, may well need planning permission in the usual way.

What prior approval looks at

Prior approval isn't a rubber stamp. The council considers a set list of matters, including transport, contamination, flood risk, noise from nearby commercial uses on the people who will live there, and whether every habitable room has adequate natural light. Others apply depending on the building and where it is.

Natural light is the one that catches office buildings out. Office floors are often deep, with windows round the outside and a dark middle. In a flat, bedrooms and living rooms need daylight, so the middle of the floor ends up as bathrooms, storage and corridors. On some floor plates there simply isn't enough window to go round.

Homes created through permitted development also have to meet the nationally described space standard. So the number of flats is set by floor area and windows, not by how many you can fit on a drawing.

Prior approval tells you the council accepts the principle. It tells you nothing about whether the building can meet building regulations as homes.

Building regulations still apply

Turning a building into dwellings counts as a material change of use under the building regulations. That brings in a long list of requirements for the new homes, including fire safety, sound insulation, ventilation, energy efficiency and drainage. This is where most of the cost and most of the design work sit.

Fire. An office is designed for people who are awake and leave together. Flats are designed for people who are asleep. Each flat is normally its own fire compartment, the common stairs and corridors need protecting, and flat entrance doors need to be fire-resisting and self-closing. An office with open floors and a single stair may need significant work to get there.

Taller buildings. If the building is at least 18 metres high or has at least seven storeys, and will contain two or more homes, it is likely to be a higher-risk building under the Building Safety Act 2022. Building control then sits with the Building Safety Regulator, and its approval is needed before work starts. That adds design time and scrutiny, so allow for it from the beginning.

Sound. Office floors were never built to stop sound between neighbours. Separating floors and walls between flats need upgrading to meet the regulations, and sound testing before completion is normally required.

Services and drainage. Offices have toilets in the core. Flats need a kitchen and bathroom each, spread across the floor, and drainage needs a fall. Whether you can get those falls within the floor-to-ceiling height, without stepping floors, is often the question that decides the layout. Each flat also needs its own heating, hot water, ventilation and metering.

What I'd look at before buying

Before anyone gets attached to a unit count, I'd look at:

• Floor plate depth and where the windows are
• Floor-to-ceiling heights, for drainage falls and services
• The number, width and position of the stairs
• The structure, and whether it can take new partitions, screeds and plant
• The condition of the roof, windows and facade
• Asbestos, in any building old enough to contain it

Sometimes the honest answer is that the building works better as offices, refurbished and relet. That route is covered in refurbishing a vacant office floor to let it faster.

Send us the floor plans

If you're weighing up a conversion, send us the floor plans, elevations, the address and some photos. We'll tell you whether the floor plate works for homes, what the building regulations side is likely to involve, and what we'd want surveyed before anyone commits to a number. Pre-construction work is where a scheme like this is won or lost, and more on how we handle change of use is on our building conversions page.