Class ZA: demolishing and rebuilding a block of flats

Class ZA demolition rebuild flats schemes are narrower than the headline suggests. The right permits one detached building to come down and one detached building to go up in its place, within the old footprint, up to 7 metres taller than what was there and never above 18 metres overall. The old block has to have been built on or before 31 December 1989, its footprint must be no more than 1,000 square metres, and it must have stood vacant for at least six months before you apply.

Read those limits as a filter rather than as a design brief. On most sites one of them is fatal, and the ones that pass are typically a single 1960s or 1970s block on a generous plot where the owner wants more homes in a better building without a full planning application.

What Class ZA permits and its footprint limits

Class ZA of Part 20 of Schedule 2 to the GPDO 2015 permits demolition of a single purpose-built detached block of flats, or a single detached building in office, research and development or light industrial use, and the construction in its place of either a single purpose-built detached block of flats or a single detached dwellinghouse.

The constraints that decide feasibility:

• The footprint of the new building must not exceed the footprint of the old one. Not the floorspace, the footprint. You gain floorspace through height, not through spread.
• The old building's footprint must be no more than 1,000 square metres.
• The old building must have been constructed on or before 31 December 1989.
• Both old and new must be detached and must be a single building. A pair of blocks is two buildings and outside the class.
• The old building must have been used for a single purpose. Mixed-use blocks with a shop at ground floor are excluded.

The word detached does more work than people expect. A block joined to a neighbouring structure by a covered walkway or a shared refuse store can be argued either way, and the answer governs whether the right exists at all.

Measure the existing footprint properly, from a measured survey rather than from a title plan, because the new building is pinned to it.

Height restrictions and the existing building envelope

The new building may be up to 7 metres taller than the highest part of the old building, subject to an absolute cap of 18 metres.

That produces three distinct situations. A two-storey building of around 7 metres can become roughly 14 metres, which is four or five storeys, and the right is worth having. A four-storey building at 12 metres can reach 18 metres but no further, so the gain is one or two storeys. An existing building already at or above 18 metres gains nothing at all.

Work the arithmetic on the real envelope. Height is measured to the highest part of the roof, and the new building's total has to include the roof structure, plant enclosures, lift overrun and parapet. A scheme designed to 18 metres at the main roof and then given a 2 metre plant screen is outside the class.

The 18 metre figure also matters for a second reason. A residential building of 18 metres or more, or at least seven storeys, falls within the higher-risk building definition used by the Building Safety Act 2022 regime, so a scheme designed right up to the cap lands in the most heavily regulated category at building control stage. Designing to 17 metres rather than 18 is often the better commercial decision, and the fire safety implications are worth checking against the Fire Statement requirements for the planning route you are using, since a licensed or competent fire engineering professional is legally required for that document under the Building Safety Act framework and the Development Management Procedure Order.

Prior approval matters including design and amenity

The council cannot refuse on general planning grounds. It can only consider the prior approval matters listed in the class, and for Class ZA that list is long:

1. Transport and highways impacts.
2. Contamination risks on the site.
3. Flooding risks on the site.
4. The design of the new building, including its external appearance.
5. The provision of adequate natural light in all habitable rooms of the new building.
6. Impact on the amenity of the new building and of neighbouring premises, including overlooking, privacy and loss of light.
7. Impact of noise from any commercial premises on residents of the new building.
8. Heritage and archaeology impacts.
9. The method of demolition.
10. Plans for landscaping, including tree planting and replacement.
11. Air traffic and defence asset impacts, and whether a protected view would be affected.

Design and external appearance being in scope is what distinguishes Class ZA from the older prior approval routes. An officer can refuse a poorly designed block, and many have. Submit the application as if it were a planning application for design purposes: contextual elevations, materials, a bay study and a landscape proposal.

Natural light in all habitable rooms is the technical item most often failed. A deeper plan on the same footprint with more storeys produces inner rooms, and single-aspect north-facing units at the lower levels of a taller building perform badly. Run the daylight analysis before you fix the unit mix.

Contamination is in scope too, so where the site history suggests a risk a desk study at least is needed, and PlanScope's draft of a land contamination assessment is a starting point for the suitably qualified person who must prepare it rather than a substitute for them.

Vacant building conditions and the qualifying period

The old building must have been vacant for at least six months immediately before the date of the prior approval application.

Evidencing vacancy is the part that trips applicants. Council tax and business rates records, utility consumption data showing no usage, tenancy records showing the date the last occupier left, and dated photographs are the usual bundle. A single statement from the owner is not enough, and councils do check.

The six-month vacancy requirement also creates a planning problem of its own. Deliberately emptying a block of flats to use Class ZA raises questions about the displacement of existing residents, and while that is not a prior approval matter, it can attract representations and political attention that affect how the application is handled.

The vacancy test works much like the one in the commercial-to-residential route, and the evidential approach set out in Class MA vacancy and continuous use conditions transfers across.

Watch the interaction with the Community Infrastructure Levy. Existing floorspace can usually be deducted from the chargeable amount only where the building has been in lawful use for at least six continuous months within the three years ending when permission first permits development. A block vacant for exactly six months may still satisfy that test from earlier occupation, but one empty for two years will not, and losing the deduction on a block of this size is a material cost. Check the levy position before you set the application date.

Construction management and demolition method

The method of demolition is a prior approval matter, which makes the demolition statement part of the application rather than a later condition.

Cover the sequence of works, the plant to be used, the arrangements for asbestos survey and removal, dust suppression, noise and vibration control to the construction noise standards, hours of working, hoarding and scaffold position, wheel washing, and the routing of demolition and construction traffic. Where the block adjoins other buildings, add a statement on party structures and monitoring.

Class ZA also carries a completion deadline. Both the demolition and the construction of the new building must be completed within three years of the date of prior approval, which is a short programme for a scheme of this kind once demolition, remediation and construction are added together. Build the deadline into the development appraisal, because overrunning it leaves the new building without the benefit of the right.

Landscaping is in scope as well, including tree planting and replacement, so a scheme that clears mature trees from the surrounds of a 1970s block needs a replacement strategy in the submission.

Where a full application remains preferable

Four situations point to a full application instead.

The scheme needs more footprint. Any increase in footprint takes it outside the class, and on most redevelopment sites a reconfigured footprint delivers far more homes than a taller version of the same plan.

The site is on article 2(3) land or otherwise excluded. Conservation areas, National Parks, National Landscapes, the Broads, World Heritage Sites, sites of special scientific interest, listed buildings and scheduled monuments all remove the right.

The design ambition needs flexibility. A full application lets you rethink the relationship to the street, the entrance position and the massing, none of which a footprint-locked rebuild allows.

Or the planning gain argument favours engagement. A full application brings affordable housing requirements and section 106 obligations, which is the cost, and in return it brings negotiation, a committee route and the ability to secure a larger scheme. Where the uplift available under Class ZA is one storey, the obligations avoided may be worth less than the extra units a negotiated scheme delivers.

Check the biodiversity net gain position for the route you choose as well, since the regime treats permission granted by development order differently from permission granted on application, and the current guidance should be verified rather than assumed.

Prior approval applications under Class ZA are determined within a statutory period, and the fee and submission requirements are set out in the procedure order. Your Planning Statement should address each prior approval matter in turn under its own heading, because an officer working through a long statutory list will look for exactly that structure.

This is general guidance, not legal advice. 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. For specialist technical reports, qualified professional input may be required. Enter your postcode on PlanScope to see which reports a Class ZA rebuild is likely to need.