Office to flats: the Class MA conditions that catch schemes
Office conversions under Class MA usually fail on prior use, vacancy, the floorspace cap or natural light. Here is how to test each condition before spending money.
Most office to residential schemes that fail under Class MA fail on one of four conditions: the building was not in Class E use for two years, it was not vacant for three months, the floorspace changing use exceeds 1,500 m², or the rear of the floorplate cannot be given adequate natural light. The first three are checked in an afternoon. The fourth needs a layout study before any money is spent, because it is the one condition where a building can satisfy every other requirement and still be refused.
Class MA sits in Part 3 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015. Work through its conditions in order before you commission anything.
The vacancy and prior use conditions
The building must have been in a use falling within Class E for a continuous period of at least two years ending on the date of the prior approval application. Offices moved into Class E(g)(i) when the use classes were restructured in 2020, so a conventional office qualifies, and so does a mixed building where the relevant part has been in Class E use.
It must also have been vacant for a continuous period of at least three months immediately before the application date. Vacant means vacant, and the authority is entitled to ask for evidence: marketing records, business rates correspondence, utility readings, lease surrender documentation.
Two practical traps sit here. A building occupied by a single remaining tenant on a short arrangement is not vacant, and a licence granted to a meanwhile user to deter squatters can break the vacancy period. Where part of a building is in Class E use and part in storage or industrial use, only the Class E part can change under Class MA, and buildings running two uses on a timetable raise their own classification questions, as set out in alternating uses in one building.
The floorspace cap in practice
The cumulative floorspace changing use must not exceed 1,500 m². That is a cap on the total across the building rather than per application, so a phased approach does not get round it.
On a typical 1980s office building the cap bites at around three to four floors. Larger buildings have to choose: convert part under Class MA and leave the remainder in Class E, or submit a full planning application for the whole building.
Converting part has consequences worth modelling. A building with flats on the lower floors and vacant offices above is harder to let, and the residual office floors need their own service core, refuse route and access arrangement. Check the cap against gross internal area measured from the drawings rather than from the agent's particulars.
Natural light to habitable rooms
This is the condition that defeats office conversions, and it is a prior approval matter the authority must consider rather than a condition you can argue around.
Office floorplates were designed for artificial light and deep plan working. A 18 metre deep floorplate with a central core produces flats whose bedrooms sit 10 metres from the nearest window, and no amount of specification solves that. The responses that work are structural: cut a light well, remove part of a floorplate to create a courtyard, place circulation in the dark zone and habitable rooms on the perimeter, or accept fewer and larger units.
Evidence needs to be quantitative. A room-by-room schedule with room depth, window area, glazing ratio and orientation, supported by daylight modelling where the geometry is marginal, is what persuades an officer. The methodology is the same as for a Daylight and Sunlight Assessment on a new build scheme, applied room by room to the existing shell.
Watch the window geometry of the existing building too. Deep reveals, solar control glazing with low visible light transmittance, and spandrel panels that look like glazing from outside all reduce the light actually reaching the room.
Noise from neighbouring commercial uses
The Order requires the authority to consider the impact of noise from commercial premises on the intended occupiers. On an office building in a town centre or on an industrial estate, that is a real assessment rather than a formality.
The sources that matter are plant and refrigeration on adjoining roofs, servicing and deliveries in the early morning, late-night licensed premises, and road or rail noise that an office with sealed facades never had to deal with as a residential use.
A Noise Impact Assessment measuring existing levels at the facade and setting out a glazing and ventilation specification is the standard answer. Pay attention to ventilation, because a specification relying on closed windows needs mechanical ventilation that also has to satisfy overheating requirements, and single-aspect south-facing flats behind sealed glazing are difficult on both counts at once.
Contamination and flood risk matters
Both are prior approval matters and both are narrower in scope than a full application would be, because the Order directs attention to risks in relation to the building.
Contamination is relevant where the site history includes industrial use, where the building has a basement in a former works area, or where ground floor use involved fuel or solvents. A desk study with a site walkover is normally proportionate, and a Land Contamination Phase 1 assessment will identify whether intrusive work is needed. Suitably qualified and experienced authorship is expected here, and the council will say so.
Flood risk matters where the building sits in Flood Zone 2 or 3. Residential use is more vulnerable than office use, which is the whole point: a ground floor office in a flood zone becomes a ground floor flat with bedrooms at risk. Expect to need a Flood Risk Assessment addressing safe access and egress, finished floor levels, flood resilient construction and a flood warning and evacuation plan.
| Condition or matter | What it requires | Common failure |
|---|---|---|
| Prior use | Class E use for two years before application | Part of building in storage or industrial use |
| Vacancy | Three continuous months immediately before | Meanwhile use or a remaining short-term tenant |
| Floorspace | No more than 1,500 m² cumulatively | Phasing attempted to beat the cap |
| Natural light | Adequate light to all habitable rooms | Deep floorplate with central core |
| Noise | Effect of commercial noise on occupiers | Plant on an adjoining roof, no ventilation strategy |
| Space standards | Compliance with the described space standard | Units squeezed to raise the count |
| Completion | Development completed within three years | Funding delay after prior approval |
Space standards and the unit mix
A condition attached to Class MA requires the development to comply with the nationally described space standard. That covers minimum gross internal areas by bedroom and occupancy, minimum bedroom sizes, built-in storage and floor-to-ceiling height.
On a deep office floorplate the space standard and the natural light requirement pull in opposite directions. Larger units reduce the number of windowless rooms and are easier to light, but they reduce the unit count and the appraisal.
Resist the temptation to resolve it by proposing a different residential use. Class MA permits change to Class C3 dwellinghouses only, so co-living, student accommodation, aparthotels and most care models are outside it, and the boundary between residential classes is less obvious than it looks, as discussed in retirement villages and the C2 to C3 boundary.
Where the building is 18 metres or more in height, the Building Safety Act regime applies at construction stage whatever the planning route, so take fire engineering advice on feasibility before committing. Check whether a fire statement is required for the particular application type you are making.
Where an Article 4 direction removes the right
A number of authorities have made Article 4 directions removing Class MA across defined areas, typically town centres, designated employment areas and secondary office cores. Where one applies, the scheme needs a full planning application and the authority's employment land policies then apply in full.
Check the direction on the authority's own policies map and read its wording, because directions vary in what they remove and in the area they cover. Some remove Class MA entirely, some remove only part of the class, and boundaries can run down the middle of a street.
Two further points on timing. A prior approval application must be determined within 56 days, and development must be completed within three years of the prior approval date. Fees are set by the national fee regulations and indexed annually, so check the current schedule rather than a figure from a previous scheme.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. A Lawful Development Certificate is the only formal way to confirm that an existing use is lawful, which matters where the two-year Class E history is uncertain.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
How long must an office have been vacant for Class MA?
Three continuous months immediately before the date of the prior approval application, on top of two years of Class E use. Authorities ask for evidence such as marketing records, rates correspondence and lease documentation. A meanwhile use or a remaining short-term occupier can break the vacancy period and restart the clock.
Does the 1,500 square metre cap apply per application?
No. It is a cap on cumulative floorspace changing use in the building, so splitting a larger conversion into phases does not avoid it. On a typical 1980s office building the cap is reached at around three to four floors, which forces a choice between partial conversion and a full planning application.
Why does natural light defeat office conversions?
Office floorplates were designed for deep plan working under artificial light. A deep plan with a central core produces habitable rooms many metres from a window, and Class MA makes adequate natural light to all habitable rooms a matter for prior approval. The fixes are structural: light wells, courtyards, or fewer, larger units.
Can Class MA deliver student housing or co-living?
No. Class MA permits a change to Class C3 dwellinghouses only. Student accommodation, co-living, aparthotels and most care models sit outside C3, so they need a full planning application. The boundaries between residential classes are less obvious than they appear and are worth checking early.
What if an Article 4 direction covers the building?
The permitted development right is removed in that area and a full planning application is needed, with the authority's employment land policies applying in full. Read the direction's wording and extent on the policies map, because some remove the whole class, some only part, and boundaries can run down the middle of a street.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.