How Much Does a Double Storey Extension Cost in Manchester? (2026 Guide)

A double storey extension is one of the most cost-effective ways to significantly increase living space in a Manchester home. By building up as well as out, you add two floors of usable space from a single set of foundations and a single roof — which is why the cost per square metre works out better value than two separate single-storey builds.

This guide gives you realistic 2026 costs for double storey extensions in Manchester, explains what drives the price up or down, and covers the planning rules that apply when you build to two storeys.

Double Storey Extension Costs in Manchester (2026)

In Greater Manchester, a double storey extension typically costs £1,800–£2,600 per m² for a standard to mid-range build, fully constructed including groundworks, structure, roof, windows, and external finish. This figure excludes VAT, professional fees, and internal fit-out.

These are honest mid-market figures for Greater Manchester in 2026. Manchester sits below London and the South East for build costs, but above rural areas — local labour rates, material transport, and planning context all pull the figure into a broadly consistent regional range.

A double storey extension costs roughly 50–75% more in total than a comparable single storey build, but costs less per m² because foundations and roof structure are shared across both floors. For a detailed comparison of single storey costs, see our house extension cost guide for Manchester.

Why Double Storey Works Out Better Value Per m²

The economics of building up rather than just out are straightforward. The most expensive elements of any extension — groundworks, foundations, and the roof — are fixed costs that don’t double when you add a second storey. A double storey build adds approximately 50–75% to the cost of a single storey, but delivers 100% more floor area from the same footprint.

For Manchester homeowners where garden space is limited — particularly on terraced and semi-detached properties in areas like Stretford, Chorlton, Salford, and Sale — this makes double storey the most space-efficient option when you need significant additional space.

If you’re planning to extend at some point in the future, it’s almost always more cost-effective to build both storeys at the same time. Adding a second storey to an existing single-storey extension later requires re-roofing and structural alterations that cost significantly more than building it correctly from the outset.

What’s Included in the Cost

A properly scoped double storey extension quote should include:

• Groundworks and foundations — excavation, concrete strip or raft foundations depending on ground conditions. Manchester’s clay-heavy soil in many areas requires careful foundation design.
• Structure — brickwork or blockwork outer leaf, insulated cavity wall, internal blockwork, floor joists and flooring to first floor
• Roof — structural roof, felt, battens, and tiles or slates to match the existing property
• Windows and external doors — standard double-glazed units; bespoke or bi-fold glazing is priced separately
• First fix — structural openings, lintels, RSJ steels where required, drainage connections
• Scaffolding — essential for two-storey builds; typically £1,500–£3,000 depending on access and duration

What’s typically not included in a shell-only build quote:

• VAT (20% on top of all labour and materials)
• Architect and structural engineer fees (typically £3,000–£8,000 combined)
• Planning application fees (currently £258 for a householder application in England)
• Internal plastering, electrics, plumbing, and heating
• Kitchen or bathroom fit-out
• Decoration and floor finishes

Adding internal fit-out to a standard build quote typically adds £15,000–£40,000 depending on specification. Kitchen fit-out alone runs £5,000–£20,000.

Planning Permission for a Double Storey Extension in Manchester

Unlike many single-storey rear extensions, double storey extensions almost always require full planning permission. Permitted development rights for two-storey builds are tightly restricted:

• A two-storey rear extension cannot extend beyond 3 metres from the original rear wall of the house
• It cannot be within 7 metres of the rear boundary
• The roof pitch must match the existing house as closely as practicable
• Any upper-floor windows on a side elevation must be obscure-glazed and non-opening below 1.7 metres from floor level

In practice, most meaningful double storey extensions exceed the 3 metre permitted development limit, making a planning application the expected route. Applications typically take 8–10 weeks to determine. In conservation areas — parts of Didsbury, Chorlton, Altrincham, and Sale have conservation area designations — design requirements are stricter and some permitted development rights are removed entirely.

For a full breakdown of the planning rules, see our guides on planning permission for house extensions in Manchester and the 6 metre extension rule.

What Drives the Cost Up

Ground conditions. Poor or variable ground conditions — common in parts of Manchester built on clay or near former industrial land — require deeper or wider foundations, structural engineer input, and sometimes ground investigation surveys before work can begin. This can add £3,000–£8,000 to groundworks costs.

Structural steels. Opening up the existing ground floor to connect to the extension, removing load-bearing walls, or spanning large openings all require RSJ steels and structural calculations. Each steel beam installation typically adds £800–£2,500 depending on span and complexity.

Brick matching. Matching the brick type, colour, and texture on a Manchester semi or terrace built pre-1950 is important for planning compliance and visual result. Sourcing period-appropriate brick can add to material costs but is usually non-negotiable for planning purposes in older areas.

Specification uplift. Aluminium bi-fold or sliding doors, flat roof sections with roof lights, high-spec insulation beyond Building Regulations minimum, underfloor heating — each element adds to the base cost. The gap between a standard and premium build is largely driven by glazing, floor finishes, and kitchen/bathroom specification.

Access and site constraints. Restricted rear access, tight-terrace gaps, or proximity to neighbouring boundaries all add to labour time and sometimes require specialist equipment.

Does a Double Storey Extension Add Value?

Yes — consistently. A well-designed and well-built double storey extension typically adds 10–20% to a Manchester property’s value. With average house prices across Greater Manchester sitting at around £250,000 in 2026, an extension costing £70,000–£100,000 can realistically add £25,000–£50,000 in value while transforming how the property functions day to day.

The return is strongest when the extension adds a bedroom and bathroom to a property that was previously undersized for its area — converting a 3-bed into a 4-bed, or a 2-bed into a 3-bed, in a neighbourhood where that size commands a premium.

Getting an Accurate Quote

Double storey extension pricing cannot be reliably given over the phone. Ground conditions, existing structure, site access, and specification choices all affect the number significantly. Any quote given without a site visit should be treated as a rough indication only.

When comparing quotes, check that scaffold, structural engineer coordination, and building control fees are either included or clearly accounted for. A quote that looks significantly cheaper than others is usually excluding something material.

Reliable Builders Ltd has been carrying out house extensions across Greater Manchester since 1974. We manage the full process from planning through to handover. Get in touch for a free, no-obligation quote.