House Extension Cost London 2026 | Complete Pricing Guide

How Much Does a House Extension Cost in London in 2026?

A house extension cost in London can vary significantly depending on the type, size, and specification of the project. In London, where moving costs and stamp duty are extremely high, extending your current home is often the more practical and cost-effective choice. This guide provides detailed pricing for house extensions in London in 2026. For more information on planning requirements, visit GOV.UK planning guidance.

Average House Extension Cost London – By Type

• Side return extension: £20,000 to £40,000 – Infills the narrow side passage alongside terraced and semi-detached properties
• Single-storey rear extension: £30,000 to £60,000 – Extends the ground floor into the garden
• Wrap-around extension: £40,000 to £70,000 – Combines rear and side return extensions
• Double-storey extension: £50,000 to £100,000+ – Adds space on two levels
• Over-structure extension: £25,000 to £50,000 – Builds above an existing single-storey structure
• Orangery: £25,000 to £55,000 – Brick-built extension with lantern roof

House Extension Cost London – Per Square Metre

A useful way to estimate house extension cost in London is by square metre. In 2026, typical rates are:

• Basic specification: £1,800 to £2,200 per sqm
• Standard specification: £2,200 to £2,800 per sqm
• High specification: £2,800 to £3,500+ per sqm

These rates include all structural work, finishes, and professional fees but exclude kitchen and bathroom installations.

Additional Costs to Budget For

• Architectural drawings: £1,500 to £4,000
• Planning permission application: £234 (standard fee)
• Building Regulations application: £500 to £1,000
• Structural engineer: £500 to £1,500
• Party wall surveyor: £700 to £1,500 per neighbour
• Kitchen installation: £5,000 to £20,000
• Bathroom installation: £3,000 to £10,000
• Landscaping: £2,000 to £5,000

How Much Value Does a House Extension Add?

A well-designed house extension typically adds between 10% and 20% to your property value. In many North London areas, a ground-floor rear extension that creates an open-plan kitchen-diner can add £40,000 to £80,000 to the property value. A double-storey extension adding a bedroom and bathroom upstairs alongside ground-floor living space can add even more.

How Long Does a House Extension Take?

• Side return extension: 6 to 8 weeks
• Single-storey rear extension: 8 to 12 weeks
• Wrap-around extension: 10 to 14 weeks
• Double-storey extension: 14 to 20 weeks

Get a Free House Extension Quote

At Fixiz Ltd, we provide comprehensive quotes for all types of house extensions across North London. Our pricing is transparent with no hidden costs. Contact us today for a free site survey and detailed quotation. You can also explore our house extension services for more details.

Call us: 020 7971 1318 | Email: info@fixiz.co.uk