Two-storey extension cost 2026: prices and fees

Guide prices by extension type

Prices are per m² of new floor space, counting both floors on a two-storey extension. They include VAT at 20% and cover the build to a decorated-ready finish: structure, roof, windows and external doors, electrics, plumbing, plastering and making good. Kitchens, bathroom fittings and flooring are separate. Figures below are for the West Midlands.

Type	Essential	Standard	Premium	Typical size
Two-storey rear extension	£1,840–£2,480 per m²	£2,000–£2,700 per m²	£2,400–£3,240 per m²	A 4 m × 3.5 m footprint on two floors (28 m² of new floor space)
Two-storey side extension	£1,890–£2,530 per m²	£2,050–£2,750 per m²	£2,460–£3,300 per m²	A 3 m × 7 m footprint on two floors (42 m² of new floor space)
Two-storey wraparound extension	£1,980–£2,710 per m²	£2,150–£2,950 per m²	£2,580–£3,540 per m²	An L-shaped footprint of about 28 m² wrapping the side and rear, on two floors (56 m² of new floor space)
Part single, part two-storey	£1,840–£2,530 per m²	£2,000–£2,750 per m²	£2,400–£3,300 per m²	A 6 m × 4 m ground floor and a first floor over half of it (36 m² in total)
Extension over a garage	£1,610–£2,350 per m²	£1,750–£2,550 per m²	£2,100–£3,060 per m²	3 m × 6 m of new first-floor space (18 m²)
First-floor extension over an existing single storey	£1,660–£2,390 per m²	£1,800–£2,600 per m²	£2,160–£3,120 per m²	4 m × 3.5 m of new first-floor space (14 m²)
Two-storey front extension	£2,020–£2,760 per m²	£2,200–£3,000 per m²	£2,640–£3,600 per m²	A 3 m × 2 m footprint on two floors (12 m² of new floor space)

Typical project totals (Standard spec, West Midlands)

Type	Typical total
Two-storey rear extension	£56,000–£75,500
Two-storey side extension	£86,000–£115,500
Two-storey wraparound extension	£120,500–£165,000
Part single, part two-storey	£72,000–£99,000
Extension over a garage	£31,500–£46,000
First-floor extension over an existing single storey	£25,000–£36,500
Two-storey front extension	£26,500–£36,000

How prices change by region

Labour and materials cost more in London and the South East and less in the North East and Northern Ireland. We apply these regional factors to every price on the site.

Region	Factor	Rear (typical)	Side (typical)	Over a garage
London	120%	£67,000–£90,500	£103,500–£138,500	£38,000–£55,000
South East England	110%	£61,500–£83,000	£94,500–£127,000	£34,500–£50,500
East of England	103%	£57,500–£78,000	£88,500–£119,000	£32,500–£47,500
South West England	103%	£57,500–£78,000	£88,500–£119,000	£32,500–£47,500
West Midlands	100%	£56,000–£75,500	£86,000–£115,500	£31,500–£46,000
East Midlands	98%	£55,000–£74,000	£84,500–£113,000	£31,000–£45,000
North West England	95%	£53,000–£72,000	£82,000–£109,500	£30,000–£43,500
Yorkshire and the Humber	92%	£51,500–£69,500	£79,000–£106,500	£29,000–£42,000
North East England	90%	£50,500–£68,000	£77,500–£104,000	£28,500–£41,500
Wales	92%	£51,500–£69,500	£79,000–£106,500	£29,000–£42,000
Scotland	94%	£52,500–£71,000	£81,000–£108,500	£29,500–£43,000
Northern Ireland	88%	£49,500–£66,500	£76,000–£101,500	£27,500–£40,500

Specification levels

Essential (92%): Good-quality standard finishes, matching brick or render, uPVC windows.
Standard (100%): Our usual spec: matching materials, aluminium or high-grade uPVC glazing, upgraded insulation.
Premium (120%): Larger glazing, architectural finishes, more structural steel and higher-spec fittings.

Common extras

Extra	Guide cost
En-suite shower room upstairs	£5,500–£11,000
Large sliding or bi-fold doors	£4,000–£9,000
Juliet balcony	£1,200–£2,500
Underfloor heating (ground floor)	£1,500–£3,500
Wide open-plan opening into the house	£3,000–£7,000

Design, engineering and approval fees

Item	Typical cost
Planning drawings (survey and design)	£2,000–£3,500
Building regulations drawings and specification	£1,500–£4,000
Structural engineer (calculations and beam design)	£750–£2,200
Building control or building warrant fee	£800–£1,900
Party wall surveyor, one agreed surveyor (England and Wales only)	£1,300–£1,500 plus VAT

Planning application fees

England: £548 (or £575 for applications made from 8 December 2026)
Wales: £585
Scotland: £371
Northern Ireland: £347

A lawful development certificate for a proposed extension in England costs £274 (about £288 for applications from 8 December 2026).

How to use these numbers

Use the guide price to decide whether a project is worth exploring, not to compare quotes line by line. Ground conditions, drains, trees, steelwork and access all change the final figure. Keep a contingency of around 10%. We price the design stage in writing before it starts, and fix the build price in writing once the drawings and calculations are agreed.

Our bands are our own, informed by 2026 published cost guides from Job Prices, MyJobQuote and BestBuilders.

Questions people ask

Why are prices quoted per m² of new floor space?

Because that's what you are buying. On a two-storey extension we count both floors, so a 4 m by 3.5 m footprint gives 28 m². It lets you compare a rear, side or over-garage extension on the same basis.

Do the prices include VAT?

Yes. Every price on this site includes VAT at 20%, which applies to most building work on existing homes.

What isn't included?

Kitchens, bathroom sanitaryware (except where an en-suite is listed as an extra), flooring, decoration, landscaping, and design, engineering and approval fees, which are listed separately.

Why is a two-storey extension cheaper per m² than a single-storey one?

The foundations and roof are among the most expensive parts of any extension. On two storeys they serve twice the floor area, so the cost per m² falls even though the total rises.

Two-storey extension prices