Double-Storey Extension Cost UK: 2026 Prices by Size
A double-storey extension costs from £44,000 in 2026, with typical projects running £44,000-£67,500 by region. You pay roughly 1.5-1.6× the single-storey price for double the space, around 20 percent less per square metre. Below: real 2026 prices by footprint, floor area and type, plus the materials split, from live pricing across 519 UK towns.
- ✓ From £44,000, all prices include VAT at 20%
- ✓ Every common footprint, 3m×4m to 6m×6m
- ✓ Rear, side, wrap-around and second-storey additions
- ✓ Free quotes from vetted local builders
Double-Storey Extension Cost UK 2026: Quick Answer
A double-storey extension costs from £44,000 in 2026, with a typical regional range of £44,000-£67,500 for a modest project; a standard 4m×4m build (32m² over two floors) runs £53,000-£64,000 and a 50m² two-storey extension costs £74,000-£90,000 at standard specification. That is around £1,480-£2,250 per m² of total floor area, roughly 20 percent below single-storey extension rates (£1,650-£4,200/m²). Materials make up about 40-45 percent of the total, and adding a second storey on top of an existing single-storey structure is a different job: budget £1,900-£3,000 per m² plus structural checks. All prices include VAT at 20 percent.
Jump to: By footprint · By floor area · By type · Adding a storey · Calculator · Materials split · Double vs single · Regions · FAQs · Free quotes
Double-Storey Extension Cost by Footprint
The footprint is the ground area the extension occupies; a double storey gives you that area twice, so a 4m×4m footprint delivers 32m² of new floor space. The table shows all-in 2026 build costs including VAT, typical professional fees and standard groundworks. Standard means brick and block, uPVC glazing, plastered and decorated. Premium adds high-spec glazing, underfloor heating, a bathroom or high-end finishes.
The low end of each range reflects competitively priced regions (the North, Wales, Scotland); the high end is typical of southern England, with London often 10-15 percent above it; see the regional section.
| Footprint | Total floor area (both floors) | Standard spec (2026) | Premium spec (2026) |
|---|---|---|---|
| 3m × 4m | 24m² | £44,000 - £54,000 | £54,000 - £68,000 |
| 4m × 4m | 32m² | £53,000 - £64,000 | £64,000 - £82,000 |
| 4m × 5m | 40m² | £62,000 - £76,000 | £76,000 - £98,000 |
| 5m × 5m | 50m² | £74,000 - £90,000 | £90,000 - £118,000 |
| 6m × 4m | 48m² | £72,000 - £87,000 | £87,000 - £113,000 |
| 6m × 6m | 72m² | £100,000 - £124,000 | £124,000 - £162,000 |
The 4m×4m row is the most commonly quoted footprint in our dataset: kitchen-diner downstairs, double bedroom upstairs, and it fits most suburban gardens. Note how the per-m² rate falls as projects grow, from £1,833-£2,250 at 24m² to £1,389-£1,722 at 72m², because design, scaffolding and site setup cost much the same at any size.
Total Cost by Footprint, Standard Specification
2 Storey Extension Cost by Total Floor Area
If you think in floor area rather than footprint, use this table. Figures are for the combined area of both floors, so a 40m² two-storey extension has a 20m² footprint. For more size steps, see our extension cost by size guide.
| Total floor area | Example footprint | Standard spec (2026) | Premium spec (2026) |
|---|---|---|---|
| 30m² | 3m × 5m | £48,000 - £60,000 | £60,000 - £78,000 |
| 40m² | 4m × 5m | £62,000 - £76,000 | £76,000 - £98,000 |
| 50m² | 5m × 5m | £74,000 - £90,000 | £90,000 - £118,000 |
| 60m² | 6m × 5m | £86,000 - £105,000 | £105,000 - £138,000 |
| 80m² | 8m × 5m | £109,000 - £136,000 | £136,000 - £178,000 |
The 50m² two-storey extension, answered directly: £74,000-£90,000 at standard specification in 2026, or £90,000-£118,000 with premium finishes. That is a 5m×5m footprint, £1,480-£1,800 per m². If a 50m² two-storey extension cost calculator quotes far below £70,000 all-in, check whether it excludes VAT, fees or second-fix trades.
Rear, Side and Wrap-Around: 2 Storey Extension Costs by Type
Where the extension sits on your plot changes the price as much as its size. Adding a storey on top of an existing structure is covered in its own section below.
| Type | Typical size (total) | Typical cost (2026) | Per m² | What drives the price |
|---|---|---|---|---|
| Rear double-storey | 24 - 50m² | £44,000 - £90,000 | £1,480 - £2,250 | The baseline: best access, simplest roof junction, sometimes permitted development. |
| Side double-storey | 20 - 36m² | £40,000 - £75,000 | £1,700 - £2,400 | Narrow footprint lifts the rate; party wall and drain moves common; always needs planning. |
| Wrap-around double-storey | 50 - 80m²+ | £90,000 - £160,000 | £1,700 - £2,200 | Rear plus side in one: corner steels, bigger roof, longest programme. |
| Second storey on an existing structure | 20 - 40m² added | £38,000 - £120,000 | £1,900 - £3,000 | Foundations must be proven; roof off; temporary weatherproofing. More complex than building new. |
2 storey side extension cost
A two-storey side extension typically costs £40,000-£75,000 in 2026 for 20-36m² of total floor space. The classic case is a garage-width strip of 2.5-3m beside a semi: utility and larger kitchen below, bedroom or bathroom above. The per-metre rate runs higher because the footprint is narrow while fixed costs are not, and boundary work often adds a party wall agreement and drain moves. Permitted development only covers single-storey side extensions, so a two-storey side extension always needs a householder planning application. Our guide to planning permission for two-storey extensions walks through the rules.
2 storey wrap around extension cost
A two-storey wrap-around extension costs £90,000-£160,000 or more in 2026 for roughly 50-80m² around the rear corner. You are building a rear and a side extension in one, tied with corner steel so the ground floor opens into one large L-shaped kitchen-living space. Steelwork, a bigger roof and five-plus months on site separate the price from a straight rear build; expect full planning rather than permitted development.
Adding a Second Storey on Top of an Existing Single-Storey Structure
This is the "2nd floor extension" search that looks like a double-storey extension but is really a different job: putting a new first floor on top of an existing single-storey extension, garage or bungalow, rather than building two new storeys from the ground up. Budget £1,900-£3,000 per m² of new floor area in 2026, noticeably more per metre than a new-build double storey, plus structural investigation costs before the job can be priced.
Why the premium? The existing foundations were designed for one storey, so a structural engineer must prove they can carry another; expect trial pits alongside the footings and, if they fail, underpinning or a steel frame. The existing roof has to come off, with temporary weatherproofing over the exposed ground floor while the new storey goes up. And you are working above a finished, often occupied space, so protection and sequencing add cost.
As a guide, a 20m² first-floor addition (a bedroom over an existing rear extension) costs £38,000-£60,000, 30m² (bedroom and en-suite over a large extension or double garage) costs £57,000-£90,000, and a full 40m² storey over a bungalow wing runs £76,000-£120,000. Figures include VAT, the new floor structure, walls, roof, windows and standard finishes; structural surveys and any foundation strengthening are extra and can only be priced after investigation.
Planning-wise, building upwards sometimes qualifies for prior-approval routes for additional storeys, but the conditions are strict and many homes fail them, so treat a full application as the default; check our two-storey planning permission guide before spending on design. If the existing structure is lightly built, demolishing and building a fresh double storey is sometimes cheaper than strengthening; price both routes.
Double-Storey Extension Cost Calculator: the Quick Method
Four steps get you within about 10 percent of a builder's ballpark, using the same per-m² method as our interactive extension cost calculator.
- Work out total floor area. Footprint width × depth × 2 storeys. A 4m×5m footprint = 40m² total.
- Pick a rate. Standard spec: £1,500-£2,250 per m² (small projects sit at the top of the range, large ones at the bottom). Premium spec: £1,900-£2,800 per m².
- Multiply. 40m² × £1,550-£1,900 = £62,000-£76,000, matching the table above; rates are all-in (VAT, typical fees, standard groundworks).
- Adjust for region. Knock 5-10 percent off in the cheapest regions; add 10-15 percent in London. Then add a 5-10 percent contingency.
Worked example for the most-searched size: a 50m² two-storey extension is 50 × £1,480-£1,800 = £74,000-£90,000 standard spec. And the entry point: a 3m×4m double storey at 24m² × £1,833-£2,250 = £44,000-£54,000, which is why UK double-storey pricing starts at £44,000 in 2026.
Materials vs Labour vs Fees: the 2 Storey Extension Cost Breakdown
If you are searching for a "2 storey extension material cost calculator", here is the honest answer: materials are 40-45 percent of the total, which means £600-£1,000 of materials per m² of total floor area at standard spec. The breakdown below is for the popular 4m×4m build (32m², roughly £58,500 mid-range).
| Cost element | Share of total | On a £58,500 project | What it covers |
|---|---|---|---|
| Materials | 40 - 45% | £23,400 - £26,300 | Concrete, brick and block, joists, roof, windows and doors, insulation, plasterboard, first and second fix |
| Labour | 35 - 40% | £20,500 - £23,400 | Groundworkers, bricklayers, carpenters, roofers, plasterers, electricians, plumbers, decorators |
| Design & professional fees | 8 - 12% | £4,700 - £7,000 | Architect or designer, structural engineer, building regulations drawings, surveys |
| Statutory & site costs | 5 - 8% | £2,900 - £4,700 | Planning and building control charges, scaffolding (from £430-£650 for a basic lift, more for a two-storey wrap), skips, site welfare |
Shares are ranges, so they will not sum to exactly 100 percent on any one project. Add a 5-10 percent contingency for what the open ground reveals.
A practical use: if a £60,000 quote itemises only £15,000 of materials (25 percent), the spec is thinner than you think or the margin is generous. And a materials-only estimate is not a build price: roughly double it and add fees for the real all-in figure.
Double vs Single Storey: Which Is Better Value?
The rule of thumb from our pricing data: a double-storey extension costs about 1.5-1.6× the equivalent single-storey footprint, for exactly twice the floor space. Foundations, groundworks, drainage and the roof are the expensive parts of any extension; a double storey buys each once and uses it twice, so the per-m² rate lands around 20 percent lower.
| Footprint | Single-storey (2026) | Single per m² | Double-storey (2026) | Double per m² | Per-m² saving |
|---|---|---|---|---|---|
| 3m × 4m | £28,000 - £34,500 | £2,333 - £2,875 | £44,000 - £54,000 | £1,833 - £2,250 | ~21% |
| 4m × 4m | £33,000 - £40,000 | £2,063 - £2,500 | £53,000 - £64,000 | £1,656 - £2,000 | ~20% |
| 4m × 5m | £39,000 - £48,000 | £1,950 - £2,400 | £62,000 - £76,000 | £1,550 - £1,900 | ~21% |
| 5m × 5m | £47,000 - £57,000 | £1,880 - £2,280 | £74,000 - £90,000 | £1,480 - £1,800 | ~21% |
Single-storey figures are typical UK ranges for these footprints; the smallest single-storey projects start from £22,000. Full pricing is in our house extension cost guide.
The strategic point: if you may ever want the upstairs space, build both storeys now. Adding a storey later costs £1,900-£3,000/m² plus strengthening, and you pay for scaffolding, roof removal and disruption twice.
What Affects a Double-Storey Extension Price
📐 Size and shape
Fixed costs (design, scaffolding, site setup) spread across more metres on a bigger build, so per-m² rates fall from about £2,250 at 24m² to under £1,500 at 72m². Simple rectangles beat L-shapes and complicated roofs.
🛁 What goes inside
An empty bedroom and landing are cheap to fit out. A kitchen, bathroom or en-suite adds plumbing, ventilation, tiling and fittings, and is the usual difference between our standard and premium columns.
🏗️ Structural openings
Opening the existing rear wall needs engineer-sized steel beams, and wrap-arounds need corner steels; each steel typically adds four figures with design, supply and fitting.
🌍 Ground and drains
Clay soils, nearby trees or poor bearing ground mean deeper foundations. Building over or near a public sewer triggers a build-over agreement, and moving manholes or soil stacks adds cost before a brick is laid.
📍 Region and labour rates
London and the South East price 20-30 percent above the cheapest UK regions for the identical drawing set, driven by labour rates and access. See the regional figures below.
🪜 Access and site logistics
A double storey always needs scaffolding (from £430-£650 for a basic lift, more for a long two-storey wrap). No side access means everything travels through the house, which slows every trade.
How to Cut the Cost of a Double-Storey Extension
- Keep the footprint a simple rectangle. Every corner, dormer or roof valley adds labour and flashing. A plain gable or hipped roof over a rectangle is the cheapest volume you can build.
- Stack the wet rooms. Put the new bathroom directly above the kitchen or utility so soil pipes and hot water runs are shared. Long pipe runs across the building are dead money.
- Build double now, not single twice. If you will ever want the space, the 1.5-1.6× rule means building both storeys today is far cheaper than a single storey now plus a £1,900-£3,000/m² top-up later.
- Take the shell, finish it yourself. Ask builders to price a weathertight, plastered shell; do decorating, flooring and fitted furniture yourself. On a £60,000 project this can trim £3,000-£6,000.
- Don't move drains if you can avoid it. Position the extension so existing manholes stay outside it; a build-over agreement and re-run drainage can swallow a kitchen's worth of budget.
- Get the design finished before tendering. Changes on paper are free; changes on site are charged at distress rates. A complete drawing set lets builders quote tight, comparable prices.
- Compare at least three itemised quotes. On identical drawings we routinely see five-figure spreads between local builders. Get three free quotes against the same specification and make them compete.
Double-Storey Extension Cost by UK Region
Our live pricing across 519 UK towns puts the typical starting range for a modest double-storey extension (around 24-30m² total, standard spec) at £44,000 in the most competitive regions, rising to £67,500 at the top of the London market; London and the South East price 20-30 percent above the cheapest regions for the same job, in line with our UK cost index.
- North East, North West, Yorkshire: £44,000 - £52,000
- Scotland, Wales, Northern Ireland: £44,000 - £53,000
- East & West Midlands: £46,000 - £55,000
- South West & East of England: £48,000 - £58,000
- South East: £52,000 - £63,000
- London: £55,000 - £67,500
Indicative for standard spec; larger footprints scale from these using the per-m² rates above.
FAQs
A double-storey extension costs from £44,000 in 2026, with a typical regional range of £44,000-£67,500 for a modest project. A standard 4m×4m build (32m² over two floors) costs £53,000-£64,000 at standard specification and a large 6m×6m build (72m²) runs £100,000-£124,000. All figures include VAT at 20%.
A 50m² two-storey extension costs £74,000-£90,000 at standard specification in 2026, or £90,000-£118,000 with premium finishes such as high-spec glazing, underfloor heating or a new bathroom. That is a 5m×5m footprint giving 25m² per floor, and it works out at £1,480-£1,800 per square metre at standard spec.
Yes. A double-storey extension costs roughly 1.5-1.6 times the price of a single-storey extension on the same footprint but delivers twice the floor area, so the per-square-metre rate is around 20 percent lower. The expensive elements (foundations, groundworks, drainage, roof) are paid for once but used by two floors.
Adding a second storey on top of an existing single-storey extension, garage or bungalow costs £1,900-£3,000 per square metre in 2026, so a 20m² first-floor addition runs about £38,000-£60,000. A structural engineer must first prove the existing foundations can carry the new storey, usually with trial pits, and the existing roof must come off with temporary weatherproofing during the build.
Often, yes. A two-storey rear extension can sometimes proceed under permitted development if it stays within strict limits, including staying within 3 metres of the original rear wall and at least 7 metres from the rear boundary, with a roof pitch matching the house. Two-storey side extensions always need a householder planning application, as permitted development for side extensions only covers single storeys.
Expect 3-5 months on site for a typical rear double-storey extension, longer for wrap-arounds or second-storey additions. Add the lead-in: design and structural drawings take 1-2 months, and a householder planning application has an 8-week statutory determination period. First sketch to finished room, 6-9 months is realistic.
A two-storey side extension typically costs £40,000-£75,000 in 2026 for 20-36m² of total floor space. The per-square-metre rate (£1,700-£2,400) is higher than a rear build because the footprint is a narrow strip while fixed costs stay the same, and boundary work often brings party wall agreements and drain moves. It always needs a planning application.
A two-storey wrap-around extension costs £90,000-£160,000 or more in 2026 for 50-80m² of new space around the rear corner of the house. The premium over a straight rear build comes from corner steelwork, a larger and more complex roof, and a longer programme, usually five months or more on site.
Materials are typically 40-45 percent of the total, which means £600-£1,000 of materials per square metre of total floor area at standard specification. Labour takes another 35-40 percent, with design fees, statutory charges, scaffolding and site costs making up the rest.
Get the design and structural drawings finished first, then put the identical pack in front of at least three local builders for itemised quotes; on identical drawings the spread is often five figures. Request your three free quotes here and compare them against the per-square-metre rates on this page.
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