Class ZA demolition and rebuild prior approval explained

Class ZA prior approval lets you demolish a single detached block of flats, or a single detached commercial building, and put a new residential building up in its place without a full planning application. It sits in Part 20 of Schedule 2 to the General Permitted Development Order 2015 and was introduced in 2020. On paper it is the most far-reaching permitted development right ever granted in England. In practice it is used rarely, and the reasons why are instructive.

The right is narrow in ways that only become apparent when you test a real site against it.

What Class ZA permits

Class ZA covers two operations taken together: demolition of a qualifying building, and construction of a new building in its place. The new building must be either a single dwellinghouse or a block of flats, and in some circumstances the previous use can be continued instead.

Both halves are permitted by the same class, which matters procedurally. You do not demolish first and then apply. The prior approval application covers the whole operation, and the authority sees the replacement building before anything comes down.

The right is exercised by applying to the local planning authority for prior approval of specified matters. It is not a notification. The authority can refuse, and a refusal carries a right of appeal.

The building types and the date limits

Only certain buildings qualify. The building must be detached and must be a single purpose-built block of flats, or a single building used for offices, research and development, or industrial processes.

Two dates apply. The building must have been built before 1 January 1990, and it must have existed on 12 March 2020. A building put up in 1992 is outside the class however unloved it is, and so is a building constructed after the 2020 cut-off. There is no route to bring either within it.

The building also has to be vacant. The class requires vacancy for a continuous period immediately before the prior approval application, which is where most schemes fall over rather than on the dates.

Height, footprint and volume constraints

The dimensional limits are the reason the arithmetic rarely works.

Read the footprint rule carefully. The new building must sit within the footprint of the old one, so you cannot square off an awkward plan, add a lift core on the flank or push out a ground floor. Any uplift in floorspace has to come from the additional height, which is capped at seven metres and at 18 metres absolute.

Eighteen metres is also the threshold where the higher-risk building regime bites for fire safety, so a scheme designed to the ceiling of Class ZA sits right at the edge of Gateway One and the Building Safety Regulator's involvement. The practical effect of that on programme is set out in building safety regulator gateways for planning teams.

The prescribed matters for prior approval

Part 20 lists what the authority may consider. The list is long enough that a Class ZA application is closer to a full application than the phrase permitted development suggests. It covers transport and highways, contamination, flood risk, the external appearance of the new building, the amenity of the new building and of neighbouring premises including overlooking, privacy and loss of light, air traffic and defence assets, noise from commercial premises affecting the new occupiers, the introduction of residential use in an area the authority considers important for general or heavy industry, storage, distribution or waste, means of access for the fire service, and the adequacy of natural light in all habitable rooms.

Later amendments to Part 20 added requirements about natural light in habitable rooms and about new dwellings meeting the nationally described space standard.

In evidence terms that means a contaminated land assessment on a former industrial site, a flood risk assessment where the site falls in Flood Zone 2 or 3, a transport statement, a noise assessment where commercial neighbours remain, and a daylight and sunlight assessment covering both the neighbours and the internal light in the new flats. A construction management report dealing with demolition method, hours and dust and noise control is also part of the submission.

Part 20 sets its own procedure for prior approval, including the information to be submitted, notification of neighbours and the period for determination. Read that procedural paragraph alongside the class, because the timescales and the consequences of a failure to determine differ between the prior approval regimes in Parts 3, 16 and 20.

Vacancy evidence and its proof

Vacancy is a question of fact and the authority will test it. Assertion in a covering letter is not evidence.

What works is a bundle: business rates records showing the empty rate period, utility bills or meter readings at negligible consumption, a marketing file if the building was on the market, dated photographs of the interior, a statutory declaration from the owner, and where there were tenants, copies of the surrender documents with dates.

What does not work is a building with a caretaker in a flat, a mast agreement generating income from the roof, or storage still in the basement. Any continuing occupation of part of the building will be raised, and the vacancy period restarts from the date the last occupation ceased.

Where the building is vacant because a tenant was removed shortly before the application, expect the authority to look at the sequence closely, particularly if the previous use was one the local plan protects.

Where the class is excluded

Class ZA does not apply on a long list of land. Conservation areas, National Parks, the Broads, National Landscapes, World Heritage Sites, sites of special scientific interest, land within the curtilage of a listed building, scheduled monuments, safety hazard areas and military explosives storage areas are all out. A listed building itself is out.

It also does not apply where the existing building is not detached, which removes most terraced and semi-detached commercial stock and every block of flats that shares a party wall.

Article 4 directions can remove the right as well, so check the authority's Article 4 register before spending anything on design.

Why the class is used less than expected

Four reasons, in the order they usually kill a scheme.

The footprint restriction caps value. A site that would take a larger building through a full application is worth more that way, and the developer only loses the certainty of the prior approval route.

The vacancy requirement costs money. Six months of empty rates and no income on a building you intend to demolish is a real holding cost, and it has to be incurred before the application is even made.

The prior approval matters are broad enough that the design work approaches that of a full application, without the flexibility to negotiate a better scheme in return.

And the financial regimes still apply. Development permitted by the order can still be chargeable development for the community infrastructure levy, and lenders and warranty providers sometimes treat a Part 20 consent with more caution than a planning permission. Because the permission comes from the order rather than from an application, some regimes that attach to a grant of permission operate differently, including the biodiversity gain condition, and the position for small sites is worth checking against the biodiversity net gain small sites rules.

None of that makes the class useless. On an isolated 1970s office block of 600 square metres, vacant after a lease expiry, in an area with a hostile local plan policy on loss of employment floorspace, Class ZA can be the only viable route. That is a narrow set of facts, which is why the class appears in so few decision notices.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it, and read the current text of Part 20 rather than a summary, because it has been amended several times since 2020. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.

Follow amendments to the order and other reforms on the PlanScope planning law timeline.