Airspace development: the sky’s the limit

Airspace development: the sky’s the limit Conversions & Extensions

Airspace developments provide existing owners and property developers with the opportunity to add new storeys onto their residential and commercial premises. Better still, the government and local authorities are keen to support property developers’ airspace development projects, particularly when they involve the creation of new apartments.

In this article, we share the basic information you need to know about airspace developments. Please book a discovery call with us to discuss your idea.


  1. What is airspace development
  2. What are the benefits of airspace development
  3. Do permitted development rights cover rooftop developments?
  4. What do local authorities think of airspace development projects
  5. Challenges to consider before building additional storeys
  6. Book a Discovery Call

What is airspace development?

An airspace development is the building of new storeys onto existing residential or commercial properties.

What are the benefits of airspace development?

The five main benefits of airspace development are:

  1. Improved saleability and value of your property
  2. Earn additional income from renting out or selling the new units
  3. More affordable and can be easier to find funding for than a demolish & rebuild project
  4. More environmentally friendly than a demolish & rebuild project
  5. Planning permission, when required, may be easier to obtain than for a demolish & rebuild project
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Do airspace developments fall under permitted development rights?

Yes. In August 2020, airspace development projects became “permitted developments” under Part 20 of the Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended).

The change of law came about because the government and local authorities hoped that it would make rooftop development onto existing properties an appealing option for property owners and developers.

  • Sustainable land use and biodiversity
  • Good health and wellbeing
  • Sustainable communities and social value
  • Sustainable life cycle cost

What do government and local authorities think about adding new floors to existing buildings?


Local authorities like airspace developments for the following reasons:

  • Addresses the housing shortage: This is a big opportunity to create new affordable housing and sustainable housing. In London, planners believe that building on existing blocks can add 180,000 homes to address housing supply issues.
  • Costs them nothing: For new build housing, a local authority normally has to buy land and pay for the construction costs. Here, the bill falls on property owners and developers.
  • Reduced impacts: Building on existing rooftops takes far less time than building new homes. This means minimal disruption during construction.
  • Less controversial: Older buildings get brand new use cases preventing them from having to be demolished unnecessarily.

It strengthens existing communities: It can give existing communities a new lease of life. It also means more taxpayers to send bills to meaning that servicing these areas becomes more economically viable for the council.

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Adding storeys on top of existing buildings - the challenges

Although local authorities generally now support airspace, you may need a Certificate of Lawfulness (sometimes known as a Lawful Development Certificate (LDC)) to proceed without planning permission. You will of course have to comply with Building Regulations, health and safety regulations and so on.

If you can’t get a Certificate of Lawfulness, the main issues you’ll face from a planning and construction perspective are:

  • Tenants/leaseholders: If your project does need planning permission, long leaseholders can raise their objections. The local authority may take these into account when coming to their decision.
  • Planning (the neighbours): The neighbours can be a big problem. To assuage that as much as possible, engage with them early and throughout. Address their specific concerns when practicable and share your project visualisations. Be prepared to adjust your design in some instances. Consider incentivising them with a project profit share, improving communal areas, reducing service charges and allocating them more parking spaces.
  • Construction: Assess the suitability and loading capacity of your building to determine project feasibility. Many airspace developments use modular constructions to minimise disruption and reduce construction time but they do present issues, especially in the provision of services, weather-/water-proofing and aesthetics.
  • Building height: If you add more stories to an existing building and it means the top storey is more than 11m above ground level, be careful as it becomes subject to Approved Document B of the Building Regulations in England. Your project may be blocked if you don’t address the presence, if any, of combustible materials in external walls among other issues.

From a legal perspective, you may come up against:

  • Leases: Do the airspace rights belong to the freeholder or tenants? Some leases may restrict development and alteration of a building and the location of its utility, ventilation and heating services. You should also factor in leaseholders’ right to quiet enjoyment of their property during planning.
  • First refusal rights: Your leaseholders may have the right to first refusal under the Landlord and Tenant Act 1987. If they do, they have the legal right to purchase the airspace from your first before you sell, lease or develop it.
  • Collective enfranchisement: Leaseholders may also be able to force you to sell roof space and airspace rights to them under the Leasehold Reform, Housing and Urban Development Act 1993. If they can persuade a judge that the roof and airspace have amenity value (that is, it provides recreational space and access to fresh air and natural light), they can force the price down.

Work with us on your airspace development project

Explore the value and potential of an airspace development with one of WindsorPatania’s architects.

We’ll answer your question and provide guidance on planning and construction. For any legal issues pertaining to your proposed development, we can put you in touch with experienced property solicitors.



Contact us about your airspace development


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