Two-storey extension: what changes the price

Two floors are not a stretched single storey

Cheshire homeowners asking about a two storey extension price are adding a room at ground level and a room above it, usually off the back of the house. The upper floor changes the structure, the roof and the stair. The Federation of Master Builders' two-storey extension guide of 13 January 2026 says costs typically range from £1,000 to £2,500 per square metre, and the at-a-glance line on its house extensions guide, read on 30 October 2026, says from around £1,000 to £2,500 per square metre ^[S7]^[S8]. The extensions guide does not show a publication date. The rate is not a Cheshire price. Prices vary by the job and the location, and QuoteZila does not set prices. The rest of this page explains which rules clip the design, and which lines should appear before you compare firms.

The first towns in view are Crewe, Nantwich and Sandbach. A double-height rear addition there is still a drawing, a ground condition and an access problem. Builders lead most of these jobs. Scaffolders are often a separate booking. Ask who employs them.

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Rear limits for more than one storey

The Planning Portal groups "extensions of more than one storey" on their own. They must not extend beyond the rear wall of the original house by more than three metres. They must not sit within seven metres of any boundary opposite that rear wall ^[S1].

Roof pitch must match the existing house as far as practicable. The same pitch note applies to an upper storey built on top of an extension that is already there ^[S1].

Any upper-floor window in a side elevation must be obscure-glazed, and non-opening, unless the part that opens is more than 1.7 metres above the floor ^[S1].

All side extensions of more than one storey need householder planning permission ^[S1]. You cannot rely on the single-storey side rule and then add a bedroom above it. On Article 2(3) designated land, all rear extensions of more than one storey also need householder planning permission ^[S1]. That designation covers a conservation area, an area of outstanding natural beauty, the Broads, a National Park and a World Heritage Site ^[S1].

Rules that apply to every extension still sit underneath. The work cannot rise above the highest part of the existing roof, or above the existing eaves. Within two metres of a boundary, eaves height cannot exceed three metres ^[S1]. Only half the land around the original house can be covered by extensions and other buildings ^[S1]. The original house is the one first built, or the one that stood on 1 July 1948 ^[S1]. Balconies, verandas, raised platforms, a chimney, a flue and a soil-and-vent pipe are outside the permitted development list ^[S1]. Materials on the outside must look similar to the existing house ^[S1].

Flats are not covered by these householder rights. Nor is a house whose permitted development rights have been removed by an Article 4 direction or a condition ^[S1]. Adding over 100 square metres of floor space may bring a Community Infrastructure Levy charge ^[S1]. Two floors make that floor-space test easier to trip than a single-storey room of the same footprint. Check it rather than assuming the levy is someone else's problem.

Use the Planning Portal page on extensions with your own rear-wall measurement. Three metres is a short projection once a stair and a useful bedroom are drawn inside it.

Building control, fire escape and the stair

GOV.UK is plain that building regulations approval is not planning permission, and that a project might need both ^[S2]. Construction and extension of buildings fall under the Building Regulations 2010 ^[S2]. Without approval, the compliance certificates you may want on sale can be missing, and non-compliant work can lead to prosecution of the person doing it ^[S2].

Citizens Advice tells homeowners that extending a building is a case for building regulations, and that an extension is an example of work which a competent person scheme does not swallow whole. You need the building control body on board before the start. A fee is normally due with the application, and inspection can mean a further payment ^[S3].

For a house that is not a higher-risk building, you choose the council's building control department or a private registered building control approver ^[S2]. Higher-risk buildings are those of at least 7 storeys or 18 metres, where they also contain at least two homes, or are a hospital or a care home ^[S2]. Quoting that threshold is only to stop a two-storey house being confused with it. The extension is still building work.

GOV.UK: building regulations approval. QuoteZila is not affiliated with this organisation. GOV.UK: find your local council for building control. QuoteZila is not affiliated with this organisation.

The new stair is a design item, not a furniture delivery. Where it lands, what it does to the bedroom it passes, and how people get out in a fire are questions for the designer and for building control. Do not cut a stair or open a floor from these notes. Ask the builder to include the stair, the lining and the fire doors they say are required, as lines you can see.

Scaffold for two storeys is part of the programme. Ask which elevation it stands on, how long it stays, and whether the pavement needs a licence from the council. Do not climb a neighbour's wall to "have a look" at the eaves. Leave the height work to the people who will build it.

Foundations and the party wall

A two-storey wall carries more load than a single-storey one, so the trench and the concrete are a designed element. If that excavation is near to and below the foundation level of the neighbouring building, the Party Wall etc. Act 1996 is in play. GOV.UK lists that excavation, and also new building on the boundary, among what the Act covers ^[S4].

The Act is separate from both planning permission and building regulations approval ^[S4]. Adjoining owners are informed by a party wall notice in the way the Act sets down, and they can agree or disagree ^[S4]. The readable version is GOV.UK's party wall guidance.

A rear extension on a semi-detached house can be metres away from the neighbour's foundation or hard against it. The drawing should say which. A quote that is silent on the party wall is not yet comparable with one that includes the surveyor.

Reading two-storey quotes side by side

Citizens Advice advises written quotes from at least three traders ^[S3]. A quote, on that page, is a fixed price. An estimate is a rough guess and can cost more in the end ^[S3]. A price that undercuts the others by a long way may be for different work, or from someone without the relevant experience ^[S3].

Topic	Two-storey detail to lock	Missing line means
Projection	Not more than three metres beyond the original rear wall, and not within seven metres of the opposite boundary, if you are relying on permitted development ^[S1]	The design may need a full application the quote ignores
Pitch	Match the existing roof as far as practicable ^[S1]	A flat lid on the first floor is a different planning case
Side glass	Obscure, and non-opening unless the opener is more than 1.7 metres above the floor ^[S1]	Clear opening windows on the side can be unlawful
Stair	Location, going, and what room it takes from	A shell price with "stair by others" is incomplete
Foundations	Design load for two storeys, and any party wall notice ^[S4]	The ground works can be a provisional sum with no depth
Scaffold	Elevations, duration, pavement licence	It appears later as a variation
Making good	Rooms the new opening cuts through, upstairs and down	Decoration of two rooms is often absent
VAT	Standard rate of 20% on most work to an existing house ^[S5]	Net and gross totals cannot be ranked

Citizens Advice would have you avoid paying everything at the start. If a deposit cannot be dodged, keep it to 25% or below and take a receipt, or buy the materials in your own name ^[S3]. The VAT registration threshold is taxable turnover over £90,000 across the last 12 months ^[S6]. Ask for the VAT position in writing ^[S3].

Before the scaffold goes up, tell the buildings insurer. Citizens Advice says cover can become more expensive during the work and afterwards, and that the insurer will probably ask who is building and what insurance they carry ^[S3].

Crewe's railway and a rear elevation

Crewe is known for its station and the West Coast Main Line. That does not change a rear-wall measurement. It is a way of saying the town is real and the job is still the house. Nantwich, on the River Weaver, and Sandbach, on the Trent and Mersey Canal, are the same: the water is not the foundation design.

What you should send is the distance from the rear wall to the far boundary, the position of the neighbour on a semi, and a photo of the landing where a stair might rise. If the gap from the rear wall to the boundary opposite is only just past seven metres, that is the measurement the rule is about ^[S1]. Measure your own garden. Do not describe it as typical of the town.

Jobs you might post

These are examples, not taken from real job posts.

Two-storey rear extension, three metres beyond the original wall, on a semi in Nantwich, with a new stair from the existing landing.
First-floor addition on top of a single-storey rear extension that is already built in Crewe, pitch to match the main roof, party wall to be checked.
Design and building control drawings for a two-storey extension in Sandbach, build to be priced only after the council's view.
Scaffold and temporary roof for a two-storey rear build, as its own line, so it is not hidden inside "preliminaries".

QuoteZila is free for customers and local businesses ^[QZ1].

A job can be sent to up to five matched local businesses ^[QZ2].

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Questions about two-storey extensions

How much does a two-storey extension cost per square metre?

The Federation of Master Builders' two-storey guide of 13 January 2026 says costs typically range from £1,000 to £2,500 per square metre, and the at-a-glance line on its house extensions guide, read on 30 October 2026, says from around £1,000 to £2,500 per square metre. The January guide says location, materials and design complexity change the figure. It is not a Cheshire price. Prices vary by the job and the location, and QuoteZila does not set prices.

Does QuoteZila check the businesses?

No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.

How far can a two-storey rear extension project under permitted development?

The Planning Portal says extensions of more than one storey must not extend beyond the rear wall of the original house by more than three metres, and must not be within seven metres of any boundary opposite that rear wall. The roof pitch must match the existing house as far as practicable, including an upper storey built on an existing extension. Side extensions of more than one storey need householder planning permission in any case.

What glass is required in an upper side window?

Any upper-floor window in a side elevation must be obscure-glazed, and non-opening unless the openable part is more than 1.7 metres above the floor. That is a planning limit on the Planning Portal page, separate from whatever building control asks for fire escape. Put the cill height and the glass type on the drawing the builders are pricing.

Does a two-storey addition need building regulations approval even if planning is not required?

It can. GOV.UK says you might need both permissions, because they are different. The Building Regulations 2010 cover the construction and extension of buildings. Citizens Advice says building an extension is not the sort of job that is left only to a competent person scheme, so you apply to a building control body before work starts.

Why are foundations a bigger line on a two-storey quote?

The upper floor loads the wall below, so the footing is designed for that load rather than for a single-storey lean-to. If the trench goes near and below a neighbour's foundation, GOV.UK says the Party Wall etc. Act 1996 can cover that excavation. Ask for the foundation design as a named item, and ask whether a party wall notice is part of the programme.

Should the quote show VAT separately?

Citizens Advice says a written quote should state whether the price includes VAT. GOV.UK says most builder's work on houses and flats is charged at the standard rate of 20%. Registration is required when taxable turnover for the last 12 months goes over £90,000. A two-storey build is work to an existing house, not the new-house zero-rate case that GOV.UK describes.

Part of Cost guides. All services

Related trades

Cost guides

Underpinning a house: what changes the price. In Cheshire, underpinning a house is priced from length, depth, access and the party wall. No pound total is printed. See who to ask before anyone digs.
uPVC Cladding Cost: What Changes the Price. Wall area, the profile and colour, battens, old cladding, trims and access: what moves a uPVC cladding quote in Cheshire, plus the planning points to check.

Sources

QZ1: QuoteZila product fact. QuoteZila pricing line.
QZ2: QuoteZila product fact. QuoteZila matching cap.
S1: Planning permission: extensions, Planning Portal. Accessed 2026-10-26. https://www.planningportal.co.uk/permission/common-projects/extensions/planning-permission
S2: Building regulations approval, GOV.UK. Accessed 2026-10-26. https://www.gov.uk/building-regulations-approval
S3: Before you get work done on your home, Citizens Advice. Accessed 2026-10-26. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/
S4: Party Wall etc. Act 1996 guidance, GOV.UK. Accessed 2026-10-26. https://www.gov.uk/guidance/party-wall-etc-act-1996-guidance
S5: VAT for builders, GOV.UK. Accessed 2026-10-26. https://www.gov.uk/vat-builders
S6: Register for VAT, GOV.UK. Accessed 2026-10-26. https://www.gov.uk/register-for-vat
S7: Two-storey extension costs, Federation of Master Builders. Accessed 2026-10-30. https://www.fmb.org.uk/resource/two-storey-extension-costs.html
S8: House extensions: the ultimate guide, Federation of Master Builders. Accessed 2026-10-30. https://www.fmb.org.uk/find-a-builder/ultimate-guides-to-home-renovation/house-extensions-the-ultimate-guide.html

What changes a two-storey extension price in Cheshire?