Splitting one unit into two commercial premises

Subdividing a commercial unit is usually worth doing and almost always needs an application. Two smaller shops let more easily than one large one, and the rent per square metre goes up. What landlords underestimate is that splitting one planning unit into two can be development in its own right, even where both halves stay in exactly the same use class, and the works that make the split usable generally need permission whatever the use position is.

This is the execution guide. The legal tests are set out separately in the piece on the planning tests for subdividing a commercial unit, and what follows assumes you have satisfied yourself on those and want to know what to submit and in what order.

Whether subdivision is development

Start with the planning unit. The courts have approached the question by asking what the unit of occupation is and whether the activities within it are ancillary to a single main use, an approach that traces back to the reasoning in Burdle. Where one occupier holds the whole and one main use runs through it, that is a single planning unit.

Create two separate occupations with independent access, servicing and control, and you have created two planning units. Whether that amounts to a material change of use depends on the effects in planning terms: trip generation, servicing demand, hours, noise, waste, and the character of the frontage. Doubling the number of shopfronts on a parade is a change in character that officers notice.

For dwellings the position is settled by statute, because the Town and Country Planning Act 1990 treats the use of a building as two or more separate dwellinghouses as involving a material change of use. There is no equivalent provision for commercial premises, which is why the commercial answer is fact-sensitive rather than automatic. Where the position matters commercially, a certificate of lawfulness for a proposed use or development under section 192 of the 1990 Act is the formal way to establish it.

Creating separate planning units in practice

The features that make two units two units are the ones to describe clearly in the application.

• Separate customer entrances from the street or from a common lobby
• Separate service and refuse arrangements, with bin capacity for each
• Separate sanitary provision and separate staff facilities
• Independent metering and, where needed, independent plant
• A physical division that is not readily reversible
• Separate leases and separate rating assessments

That last pair sits outside the planning system, and it is evidence of the position rather than the cause of it. A single lease over both halves with a partition that could be removed in a weekend is a weaker case for two units than two leases and a masonry wall.

Shopfront and access alterations

Internal works alone are rarely development, because the definition of development turns on building works that materially affect the external appearance or on a material change of use. The moment the split needs a second door, a new shopfront, a mullion where the glazing ran continuously, or a change to the fascia, external works are engaged.

Shopfront design is where these applications get refused. A wide traditional shopfront divided into two narrow ones can lose the proportions that made the frontage work, particularly on a historic parade. The moves that succeed are keeping the original stallriser, cornice and fascia line running across both halves, dividing with a pilaster that matches the existing rhythm rather than a plain post, and keeping the two fascias to a single depth and alignment. Where the building is listed, listed building consent is needed in addition to planning permission, and the internal division becomes part of that assessment because internal works to a listed building require consent.

New fascia signs and any illumination may also need express advertisement consent, and it is cleaner to apply for that separately than to leave signage undrawn.

Servicing, waste and parking for each unit

Two units generate more of almost everything than one did. Officers will ask for the arithmetic.

Parking standards are applied per unit, and two units of the same combined floorspace can attract a higher requirement than one. In a town centre with a controlled parking zone that may not matter. In an out-of-centre parade with a shared forecourt it frequently does, and a Transport Statement covering servicing and parking demand for both units is proportionate evidence.

Think about the likely occupiers rather than the theoretical ones. If half the unit will realistically end up as a takeaway, the extraction, odour and late-hours questions arrive with it, and applying for the split without addressing them just moves the argument to the next application.

Conditions attached to the original permission

Check the planning history before anything else. Conditions restricting subdivision are common, particularly on retail parks, industrial estates and units granted permission as a single large floorplate to protect a town centre.

Typical wording prevents the unit being subdivided into more than one retail unit, or restricts the goods that may be sold, or limits the net sales area. Where such a condition exists, the application is an application under section 73 to vary or remove it, and the council will reconsider the reason the condition was imposed. On a retail unit that reason is usually town centre impact, so expect to address the sequential test and impact policy in the supporting statement if the resulting units fall within the relevant thresholds.

Conditions on a use class basis matter too. A permission granted for a specific use before the 2020 use class changes may be tied to that use by condition, which can restrict the flexibility that Class E otherwise gives. And some uses sit outside the classes altogether, so understanding which uses are sui generis tells you what each half can actually be let to without a further application.

Building Regulations implications

Planning and Building Regulations are separate consents, and subdivision engages the Regulations comprehensively.

Means of escape has to work for each unit independently, which on a deep unit with one frontage is the technical problem that decides whether the split is viable at all. Fire separation between the units to the standard in Approved Document B, protected escape routes, accessibility and sanitary provision under the other Approved Documents, and any structural work to form openings all need a Building Regulations application. Get a designer to test escape before you spend on a planning application, because a split that cannot be made to comply is not worth pursuing.

The application pack

1. Existing and proposed floor plans and elevations, drawn to scale, with the division and each unit's area clearly marked.
2. A Planning Statement covering the planning unit analysis, the use class position for each half, the planning history and any condition to be varied.
3. Section 73 application where a condition restricts subdivision, quoting the condition in full.
4. Servicing and refuse details, with bin capacity per unit.
5. Transport and parking evidence where standards or access make it necessary.
6. A Ventilation and Extraction Statement where any half is intended for food preparation.
7. Advertisement consent application for new or altered signage.
8. Listed building consent where the building is listed, covering internal as well as external works.

Draft the supporting statement and the servicing details together, since the officer will read them as one document whatever order you submit them in. This is general guidance rather than legal advice, so check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.