Building Costs Per Square Metre in London 2026: The Complete Guide for Prime and Standard Projects
- Jul 25, 2025
- 5 min read
Updated: Jul 16
Whether you are planning a bespoke new build, high specification refurbishment, London basement or major extension, understanding current building costs per square metre is essential for confident budgeting. NU Projects has updated this quantity surveying guide for 2026 while preserving the page’s established search history.
The figures below are broad cost planning benchmarks. They are not quotations and must be tested against the actual property, drawings, structural requirements, access, programme and specification.
London building costs per square metre in 2026
Project type | Standard specification | Mid to high specification | Prime specification |
Single storey rear extension | £2,200 to £2,800 | £2,800 to £3,500 | £3,500 to £5,000 |
Loft conversion with dormer | £1,800 to £2,500 | £2,500 to £3,200 | £3,200 to £4,500 |
Full internal renovation | £1,600 to £2,400 | £2,400 to £3,200 | £3,200 to £5,000 |
Basement construction, shell only | £4,000 to £5,500 | £5,500 to £7,000 | £7,000 to £9,500 |
Detached new build | £2,200 to £3,000 | £3,000 to £4,500 | £4,500 to £6,500 |
These benchmarks exclude VAT, professional fees, furnishings and external works unless a project specific cost plan states otherwise. Basement shell figures do not include the full luxury fit out.
Prime Central London cost premiums
Location | Prime specification build cost per m² |
Mayfair | £6,000 to £8,500 |
Knightsbridge | £5,800 to £8,200 |
Belgravia | £6,200 to £9,000 |
Chelsea | £4,800 to £6,800 |
South Kensington | £4,500 to £6,500 |
Notting Hill | £4,200 to £6,000 |
Fulham | £3,200 to £4,800 |
Hampstead | £4,000 to £6,000 |
St John’s Wood | £4,500 to £6,500 |
Holland Park | £4,800 to £7,000 |
The location ranges reflect more than the postcode. Prime properties frequently require superior materials, detailed craftsmanship, heritage expertise, restricted access planning, stronger neighbour management and longer specialist procurement.
What does specification mean?
Standard specification
A controlled palette of dependable products, straightforward details and limited bespoke work. Standard does not mean poor quality, but it assumes fewer specialist systems and simpler coordination.
Mid to high specification
Better kitchens, bathrooms, lighting, services and finishes, with selected bespoke joinery and more detailed design coordination.
Prime specification
Exceptional materials, extensive bespoke joinery, specialist stone and metalwork, advanced heating, cooling, lighting and security, detailed restoration and a higher standard of site management and handover.
What cost per square metre does not tell you
Whether structural steel, underpinning or temporary works are included.
Whether the rate covers kitchens, sanitaryware, appliances and fitted joinery.
Whether mechanical and electrical systems are basic or fully integrated.
Whether the property is listed, occupied or subject to a licence to alter.
Whether VAT, professional fees and statutory costs are included.
Whether restricted hours, access, protection and neighbour requirements have been allowed.
Whether the rate is measured against gross internal area, new area or the area being refurbished.
Why building costs change
Construction costs respond to labour availability, material pricing, energy, logistics, regulation, demand and the complexity of individual projects. The 2021 and 2022 period demonstrated how quickly lead times and supplier prices can change. Those historic predictions should not be used as a current forecast, but the lessons remain valuable.
Current cost pressures to plan for
Skilled labour availability, particularly for prime finishes and heritage work.
Subcontractor prices that may be reviewed during a long design or approval period.
Heating, cooling, ventilation, insulation and sustainability requirements.
Planning, party wall, freeholder and building management costs.
Imported stone, specialist ironmongery, bespoke lighting and custom manufacture.
Long lead kitchens, glazing, joinery and mechanical equipment.
Restricted London logistics, storage and waste removal.
Procurement lessons from earlier supply disruption
The correct response to changing markets is not panic buying or an oversized blanket allowance. It is early design, package specific procurement and clear ownership of decisions.
Identify long lead items during technical design.
Obtain current supplier and specialist feedback before the cost plan is fixed.
Separate firm prices from provisional allowances.
Record quotation expiry dates and inflation assumptions.
Approve samples and technical information before manufacture.
Maintain appropriate alternatives without weakening the design.
Track procurement against the construction programme.
How NU Projects estimates a project
NU combines benchmark information with the facts of the property. Our quantity surveying approach considers measured scope, surveys, design information, specification, access, programme and live specialist feedback.
Layered cost breakdowns rather than one headline rate.
Measured quantities and transparent assumptions.
Current market feedback from relevant trades and suppliers.
Risk allowances linked to identifiable project conditions.
Provisional sums for genuinely unresolved packages.
Cash flow forecasting across design, procurement and construction.
Regular cost plan updates as decisions are made.
An example of how the same area changes cost
A 100 square metre rear extension with a simple structure and controlled specification is a different commercial proposition from the same area containing specialist glazing, complex steelwork, a bespoke kitchen, stone flooring, underfloor heating, air conditioning and restricted access. The floor area is identical; the scope is not.
This is why early cost per square metre figures should be used to test feasibility, then replaced by a measured project cost plan as the design develops.
Professional fees, VAT and contingency
Architecture, interior design, structural engineering, mechanical and electrical design, quantity surveying, project management, party wall work and statutory approvals may sit outside a construction benchmark. VAT should also be shown clearly.
Contingency should reflect surveys, design maturity and property risk. It is not a spare budget for optional upgrades and should not disguise incomplete information.
For a closer look at prime refurbishment budgeting, read How Much Does a High End Home Renovation Cost in London in 2026?.
Design and build or traditional tender?
The procurement route affects when construction knowledge enters the project and who coordinates cost, design and buildability. Design and build can identify risk earlier, while traditional tender can work well when the information is complete and responsibilities are clear.
Compare the two routes in Design and Build or Traditional Tender: Which Route Gives Homeowners More Cost Certainty?.
Frequently asked questions
What is the average building cost per square metre in London in 2026?
It depends on project type and specification. The NU Projects benchmarks range from approximately £1,800 per square metre for straightforward loft work to £9,500 per square metre for a prime basement shell. A project specific cost plan is still required.
Why are prime London costs higher?
Prime projects combine higher specifications with heritage constraints, restricted logistics, specialist trades, complex services and demanding management requirements.
Are professional fees included in cost per square metre?
Not automatically. Every benchmark must state its exclusions. Consultant fees, VAT, furnishings, external work and contingency are often separate.
How often should a cost plan be updated?
At key design stages and whenever the scope, specification, programme or market information changes materially.
Replace ballpark figures with a proper cost plan
NU Projects is the No 1 integrated choice for clients who want architecture, interiors, quantity surveying and construction aligned from the start.
For a detailed budget tailored to your property, book a confidential consultation with NU Projects.
