Building a New House in London 2025: Planning, Costs, and What the Process Really Involves

New build residential development in London is subject to strict planning control. The supply of sites suitable for new residential development in London is highly constrained — most potential development sites are either already developed, are in use as parking or garden land where development may be resisted, or are in Green Belt (where residential development is tightly controlled). Types of site where new dwelling planning permissions are granted in London: Infill plots: a gap site between two existing dwellings in a terrace or semi-detached row, or a side garden plot that is large enough to accommodate a new dwelling. Infill plots are the most common type of small new-build residential site in inner London. The planning assessment focuses on: whether the plot can accommodate a dwelling of appropriate scale and massing that is in keeping with the character of the street; whether the plot provides adequate daylight and privacy for the new dwelling and maintains adequate daylight and privacy for the neighbouring properties; the quality and amenity of the new dwelling (minimum space standards from the London Plan — nationally described space standard applies in London). Backland development: a new dwelling built behind an existing house or in a back garden. Backland development is strongly resisted in many London boroughs because of the potential harm to the character and appearance of residential streets, the creation of car-free or limited-access plots, and the impact on neighbouring amenity. Some backland plots do gain consent where the design is innovative, the site is well-screened, and the access and amenity questions can be resolved. Demolish and rebuild: demolishing an existing house and building a larger new dwelling on the same footprint. Demolish-and-rebuild is subject to planning permission — the principle of demolition and replacement with a new dwelling is generally acceptable in planning terms in London if the replacement is appropriate in size, scale, and character for the street. Conversion and change of use: converting a non-residential building to residential use (a Class MA permitted development or planning application for change of use from Class E commercial to Class C3 residential, for example). Change of use conversions in London have been a productive source of new residential supply. The planning assessment: a planning application for a new dwelling (Outline or Full Planning Application — not a Householder Application) is submitted to the LPA. The LPA assesses the proposal against: the London Plan (Mayor of London's strategic planning policies — the 2021 London Plan includes policies on housing delivery, design, sustainability, and amenity); the local plan of the relevant London borough; any site-specific material considerations. For a new dwelling in a sensitive location (conservation area, AONB, Green Belt), the design, scale, and materials are assessed very carefully. Pre-application advice from the LPA (pre-app meetings) is strongly recommended before a planning application is submitted — the cost and timescale investment in a planning application for a new dwelling is significant.

The cost of building a new house in London depends on: the size of the dwelling (gross internal area in square metres); the specification level (standard, mid, or high specification finishes and M&E systems); the site complexity (access restrictions, ground conditions, proximity to a public sewer, party wall implications, basement or underground car park requirements); the contract route (design-and-build with a principal contractor, self-build managing individual trades, or contractor-procured package). New build construction costs in London (2025, gross internal area, excluding land, professional fees, planning costs, and VAT): Standard specification (functional, contractor-grade finishes — emulsion walls, standard sanitary ware, carpet or LVT flooring, mid-range kitchen, UPVC windows, standard boiler): £2,000-£2,600/sq m GIA. Mid specification (good quality finishes — tile and hardwood floors, mid-range fitted kitchen with stone worktops, double-glazed timber or aluminium windows, combi or system boiler, quality sanitaryware): £2,600-£3,500/sq m GIA. High specification (premium finishes — natural stone or engineered oak floors throughout, bespoke joinery, premium kitchen (Bulthaup, Gaggenau), integrated home automation, underfloor heating, ASHP, triple glazing, external rendering or brick slips): £3,500-£5,000+/sq m GIA. For a 150 sq m (GIA) new build house in London (a typical 3-4 bedroom family home): Standard specification: £300,000-£390,000 construction cost. Mid specification: £390,000-£525,000 construction cost. High specification: £525,000-£750,000+ construction cost. Additional costs to budget separately: land acquisition: the dominant cost for London new build — a plot for a 150 sq m house in inner London: £400,000-£900,000+; outer London: £200,000-£500,000+ (varies enormously by location). Professional fees: architect (10-15% or fixed for a new build, covering RIBA stages 1-6+); structural engineer (£3,000-£12,000+ for a house); M&E consultant (for larger or higher-spec projects); planning consultant; CDM Principal Designer; QS/cost consultant. Planning application fee: £462 per dwelling for a full planning application (England 2024). Building Control fee: £1,000-£4,000+ for a new build house. VAT: standard rated at 20% for new build residential properties where the contractor is VAT registered. Self-builders can reclaim VAT on materials used in a new build dwelling under HMRC's DIY Housebuilder VAT Refund Scheme. Timescale: a typical new build 3-4 bedroom house in London (excluding planning): groundworks and foundations (4-8 weeks); structure — timber frame or masonry walls (8-16 weeks); roof structure and waterproofing (4-8 weeks); first fix M&E and insulation (6-10 weeks); plasterboard, plaster, and screed (4-8 weeks including drying time); second fix and finishes (8-16 weeks); external works (4-6 weeks). Total: 10-18 months on site for a standard new build house in London, excluding planning. Including planning and pre-construction: allow 18-36 months from land acquisition to occupation.

Self-build and custom build housing are specific routes to owner-occupier new build that give individuals greater control over the design and specification of their new home. The Self and Custom Build Register: under the Self-build and Custom Housebuilding Act 2015 (and as amended by the Housing and Planning Act 2016), every London borough is required to maintain a register of individuals and groups who want to acquire serviced plots to build their own homes. Registering on a local authority self-build register: (a) is free; (b) requires the LA to have regard to the level of demand shown by the register when planning for land supply for self and custom build. The Right to Build: the Act creates a duty on local authorities to grant sufficient development permissions on serviced plots to meet the demand shown on the register in a 3-year period. In practice, the Right to Build has had limited impact in London — serviced plots in London suitable for self-build are extremely scarce, and many London boroughs are unable to meet the demand shown on their registers. Self-build routes: managing your own new build house project (appointing an architect, structural engineer, and contracting individual trades — groundwork sub, timber frame package, roofing sub, M&E sub, plasterer, joiner, decorator). The self-builder acts as their own project manager. Requires significant time, knowledge, and risk appetite. Potential cost saving of 20-30% over a main contractor build, but with commensurate risk. Timber frame package build: procuring the structural shell (foundations, ground floor, walls, roof structure) from a timber frame package supplier (Potton, Huf Haus, Scandia-Hus in London, Border Oak) — the package includes the structural engineering, the panels or modules, and often the roof and external cladding. The client or their builder carries out the remainder of the work. Custom build: the client works with a developer or a specialist custom build enabler to specify their new home within a framework designed by the developer. The developer provides the plot, the planning permission, the services infrastructure, and the structural shell — the client specifies the internal layout, finishes, and M&E systems. Custom build is not yet well-established in London at scale, but some housing associations and developers have begun to offer custom build plots.