Self-Build in London: Planning, Costs, Routes to Building, and What to Expect

Self-build -- commissioning the construction of a new home rather than buying an existing or developer-built one -- is both more complex and more interesting in London than in most other UK regions. London's extremely constrained land supply, high site values, and complex planning environment make finding a suitable building plot and obtaining planning permission significantly more challenging than in suburban or rural areas. But for those who succeed, self-build in London can produce a home that is precisely tailored to the owner's needs, potentially at a lower total cost than an equivalent developer new-build would command on the open market.

Developer new build: a developer acquires land, obtains planning permission, builds a scheme of multiple units, and sells the completed homes. The buyer has no input into the design.

Self-build: the future occupier directly commissions the construction of their own home. The self-builder typically acquires the land, obtains planning permission, and manages the construction process themselves (either employing a main contractor, managing trades directly, or doing some of the work themselves).

Custom build: a variant where a developer provides serviced plots with pre-approved planning consent, and the buyer commissions the construction of their home to their own specification. The developer has arranged the land, infrastructure, and planning envelope; the buyer controls the design and construction within it. Custom build reduces the land-finding and planning risk compared with full self-build.

Right to Build: the Self-build and Custom Housebuilding Act 2015 created a Right to Build that obliges local authorities to keep a register of people seeking self-build and custom build plots, and to make sufficient serviced plots available to meet the demand. In London, this right exists but the number of available plots is extremely limited by land constraints and competing development pressures.

London building plots are rare and expensive. Common sources include:

• Gap sites and backland plots: narrow infill sites between existing buildings, rear garden plots where planning consent has been obtained for a detached dwelling, and former outbuilding sites.
• Demolition and replacement: purchasing an existing property in very poor condition, demolishing it, and building a replacement to a modern design. This is a common self-build route in inner London where plot values support the demolition economics.
• Single-unit conversions and change of use: former commercial premises (retail, office, workshop) converted to residential use under change of use or prior approval.
• Estate agents (land specialists): some estate agents specialise in London building plots and development opportunities.
• Land registry searches and direct approaches: identifying underused land or properties and making direct approaches to owners.

Planning permission for a new dwelling in London is a significant hurdle. Key considerations:

• Backland development: London councils are generally restrictive about backland development (building behind existing homes) due to concerns about loss of amenity, overlooking, and character impact. Each borough has its own policies.
• Design quality: London planning authorities typically require high-quality architectural design for new buildings in residential areas. A design that fits the character of the street and makes a positive contribution is essential.
• Sustainability requirements: new buildings in London must comply with Part L Building Regulations (minimum energy performance) and may also need to meet London Plan energy policies (SAP calculations, zero carbon or near zero carbon requirements).
• Planning policy for self-build: some London boroughs have specific policies that are supportive of self-build and custom build; others are more restrictive. Researching the relevant borough's local plan and speaking to the planning authority before acquiring a site is essential.

Traditional self-build (architect and main contractor): the self-builder appoints an architect to design the house and prepare planning and building regulations drawings, then puts the project out to tender to building contractors. The self-builder manages the professional team and contractor directly. This route provides maximum design flexibility but maximum management involvement.

Design and build self-build: the self-builder appoints a design-and-build contractor who provides both the design (often from a range of standard designs) and the construction. Less flexible on design but simpler to manage.

Package house (Huf Haus, Baufritz, etc.): a package house supplier provides a factory-engineered structural frame (typically timber or SIPs), which is erected on the self-builder's prepared foundations by the manufacturer's team. The self-builder arranges the plot, foundations, planning, and internal fit-out independently. Fast erection but a specific aesthetic.

SIPs or structural insulated panels: structurally insulated panel systems (used by companies such as Potton, Scandia-Hus, and Kingspan TEK) provide a fast-erect, highly insulated structural frame suitable for self-build projects seeking high energy performance.

London self-build costs are significantly higher than UK averages due to labour costs, ground conditions, access constraints, and planning requirements:

• Land: the dominant cost in London. An infill plot or demolish-and-replace opportunity in inner London may cost £400,000--£1,500,000+ depending on location and size.
• Construction (shell and core, traditional self-build): typically £2,500--£4,500/m2 for a well-specified London self-build, excluding land and professional fees. A 150m2 house might cost £375,000--£675,000 to build.
• Professional fees (architect, structural engineer, planning consultant, CDM coordinator): typically 12--18% of construction cost.
• Planning and legal fees: typically £5,000--£20,000 depending on complexity.

VAT: self-build new homes are zero-rated for VAT, meaning the self-builder can reclaim VAT on most construction materials and services. This is a significant financial benefit compared with buying a second-hand property (where works attract 20% VAT).

rcbGroup has experience of small-scale new residential construction in London, including replacement dwellings and infill development. We provide full design-and-build services from planning through to handover. Contact our team to discuss new build and self-build projects in London.