Class ZA Permitted Development: A Practical Guide

As working habits continue to evolve and more people operate remotely or flexibly, demand for traditional office space has fallen sharply.

For developers, this shift presents a clear opportunity — particularly in urban areas where underused commercial buildings sit on valuable residential land.

That’s where Class ZA permitted development comes in.

What is Class ZA permitted development?

Class ZA is a permitted development right that allows the demolition of certain commercial buildings or blocks of flats and their replacement with new residential development, without applying for full planning permission.

Unlike other PD rights that focus on change of use, Class ZA enables:

• complete demolition of an existing building
• construction of a new residential building in its place
• additional height through airspace development

It is one of the few permitted development routes that allows demolish and rebuild, making it particularly attractive for outdated or inefficient buildings.

What qualifies under Class ZA?

Class ZA applies to either:

• a single detached building in former Use Class B1, or
• a standalone block of flats

The existing building must have been in place on 12 March 2020.

Eligible former uses include:

• B1(a) – offices
• B1(b) – research and development
• B1(c) – industrial processes
• existing residential blocks of flats

With Class ZA, the demolished building can be replaced by:

• a new block of flats, or
• a single detached house

with up to two additional storeys in the airspace, subject to height limits.

Size and height limits under Class ZA

Class ZA comes with clear dimensional constraints.

Key limits include:

• the footprint of the existing building must not exceed 1,000 sqm
• the highest part of the existing building must be no taller than 18m

When replacing the building:

• the new structure must sit within the same footprint
• the building may be no taller than 18m in total
• or no more than 7m higher than the original building (whichever is lower)

Interestingly, a basement can be added, regardless of whether the original building had one.

How big can you go?

When planning a Class ZA scheme, two principles govern scale:

1. Footprint
   The base area of the new building cannot exceed that of the original.
   If the existing building footprint is 1,000 sqm, that is your maximum site area.
2. Height
   The replacement building may:
   • replicate the existing number of storeys
   • add up to two additional storeys
   • remain within the 7m / 18m height cap

This makes Class ZA well suited to urban intensification, particularly in town and city centres.

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What to consider when assessing Class ZA opportunities

Class ZA is powerful, but it is tightly defined. Key criteria include:

• the building must have been constructed no later than 31 December 1989
• the building must have been vacant for at least 6 months
• the existing footprint must be 1,000 sqm or less
• demolition must involve the entire building (partial demolition is not permitted)
• only one building can be demolished under each application
• the replacement building may include the same number of storeys plus two additional storeys, within height limits
• once completed, the new dwellings cannot be converted to C4 HMO without full planning permission
• Class ZA does not apply in:
  • Article 2(3) land
  • conservation areas
  • SSSIs
  • listed buildings
  • scheduled monuments
  • safety hazard areas
  • military explosives areas
  • land within 3km of an aerodrome

Early checks against these criteria are essential.

Class ZA prior approval requirements

Although full planning permission is not required, prior approval is mandatory.

Local authorities may assess:

• transport and highways impacts
• contamination risk
• flood risk
• design and external appearance
• provision of adequate natural light
• impact on neighbouring buildings and occupiers

As with other PD rights, success often comes down to context, design quality and early due diligence.

Why Class ZA matters right now

Class ZA responds directly to:

• structural oversupply of office space
• rising vacancy in urban commercial areas
• continued demand for housing in city locations

For developers, it offers:

• access to prime urban land
• a faster route to residential delivery
• the ability to replace inefficient stock entirely
• opportunities in markets where change-of-use alone isn’t viable

In many locations, Class ZA provides a rare route to full redevelopment without full planning risk.

How to source Class ZA opportunities at scale

Identifying suitable Class ZA sites manually is challenging — requiring historic use checks, vacancy confirmation, footprint analysis and constraint screening.

With Searchland, you can:

• identify vacant B1 buildings and blocks of flats
• filter by footprint size and constraints
• review planning history and surrounding context
• understand ownership and title details
• assess multiple sites quickly across towns and cities

If you’re unsure how to structure a Class ZA search, our team can help you apply the right filters and sense-check opportunities early.

TL;DR: why Class ZA should be on your radar

Class ZA permitted development allows certain commercial buildings or blocks of flats to be demolished and replaced with new homes, without full planning permission.

With office vacancy rising and urban land at a premium, it provides a powerful route to:

• unlock underused buildings
• intensify city sites
• deliver housing where demand remains strong

For developers focused on urban regeneration and redevelopment, Class ZA is a permitted development right worth close attention.

To get started,  jump on a demo with our team so they can show you our full set of features.