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Drone view of the roofs of a Belgravia terrace

Airspace Development in London: Add Storeys to Your Building

Airspace development adds new storeys on top of a building you already own, creating floorspace with no land to buy. We check the structure and planning, secure consent under Part 20 permitted development or full planning, and build it.

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What our clients say

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Schemes from £3M to £150M GDV

We assess airspace on mansion blocks and commercial buildings for schemes of this size.

Our airspace development service

Not every roof can carry a storey. We answer the two questions that decide it, planning and structure, before anyone spends on design.

  • Structural check

    Can the building and its foundations take the extra load?

  • Part 20 or full planning

    Part 20 depends on the building's age, height and type; otherwise full planning.

  • The value case

    New homes or space where the land cost is already sunk, shown in an appraisal.

  • Residents and tenants

    Access, consents and a plan for the people living or working below.

  • Rooftop construction

    Craning, access and weathering-in above a building in use.

  • Selling the airspace

    Prefer not to build? See options and promotion agreements.

How an airspace scheme runs

We review the building, its designations and the planning context.

Structure, access and design options tested and priced.

Part 20 prior approval or a full application, prepared and managed by us.

Structure, services and logistics detailed for building above occupied floors.

One team builds what was consented, so the approved scheme is the one that gets built.

Drone survey of flat roofs from above

Is there value above your building?

Send us the address. We will check the planning position and the structure question, and tell you if a storey is realistic, free.

Drone view of a corner site in St John's Wood and the streets around it

Free Airspace & Upward Extension Guide

Whether your roof can take new homes: Part 20 permitted development or full planning, plus the structural checks.

Rights of light, party walls, residents and tenants, and five ways a freeholder can take the value.

Why freeholders choose Craftex for airspace

  • Builders, not only planners

    Rooftop schemes live or die on structure and logistics; our construction team is in from the start.

  • Senior people on every scheme

    Our Preconstruction Director, Martin Hickey, brings 50+ years in construction to every appraisal.

  • The deal that suits you

    Depending on the stage we co-invest, take 100% of the risk, or work on a fee or percentage basis.

Independently Certified Contractor for Quality, Safety & Reliability

  • British Assessment Bureau
  • British Assessment Bureau certificate
  • British Assessment Bureau
  • Constructionline
  • CHAS Accredited Contractor
  • Alcumus

Airspace development: questions

Can I add a floor to my building?

Many London buildings can, either under Part 20 permitted development or with full planning permission. It comes down to age, height, structure and designations, which the free appraisal checks. Our airspace guide covers who owns it and the tests in detail.

What is Part 20 permitted development?

A set of permitted development rights (Classes A to AD) that allow new homes to be added on top of certain buildings, subject to prior approval on specific matters. Where it applies, it is a faster, more certain route than a full application. Extra storeys on a single house fall under Part 1 Class AA instead. Which buildings qualify: who owns airspace and can you sell it.

Do I need planning permission for a rooftop extension?

If Part 20 does not apply, yes, and central London schemes usually go the full-planning route. See planning permission.

Can you build above an occupied building?

Yes. We plan access, craning and weathering-in around residents and tenants, as we did at Portsoken House, delivered around occupied tenants.

What is my airspace worth?

It depends on what can be built and what it would sell for. Our appraisal shows the value with consent. See land value uplift.

Find out what your roof is worth

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