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What does a 3 metre house extension take?
In Cheshire, three metres is still a depth to price on the drawing, while Federation of Master Builders guides put a single-storey extension at £1,800 to £3,000 per square metre, not a package price for that depth [S6][S7]. Prices vary by the job and the location, and QuoteZila does not set prices.
Last reviewed:Three metres is a depth on a drawing
A Cheshire search for a "3 meter house extension" usually means a short single-storey rear room. The Planning Portal measures that depth in metres. It is a planning limit for many houses that are not detached, not a bylaw for one town and not a package a builder sells at one rate. The Federation of Master Builders' single-storey extension guide of 4 March 2026 says the UK average is between £1,800 and £3,000 per square metre, and its house extensions guide, read on 30 October 2026, gives the same £1,800 to £3,000 per square metre [S6][S7]. The extensions guide does not show a publication date. This page does not turn that rate into a total for a three metre room. It is not a Cheshire price. Prices vary by the job and the location, and QuoteZila does not set prices. What you can still compare is the depth from the original rear wall, the foundations, the drains, and whether the quote is a shell or a finished room.
Which houses the three metre line belongs to
On the Planning Portal, a single-storey rear extension must not extend beyond the rear wall of the original house by more than four metres if the house is detached, or more than three metres for any other house [S1]. The same extension must not exceed four metres in height [S1]. So a semi-detached or terraced house is the one whose ordinary rear cap is three metres. A detached house is on the four metre line unless something else bites [S1].
"Original house" matters. The Portal defines it as the house as first built, or as it stood on 1 July 1948 if it was built before then [S1]. Measure from that rear wall, not from a conservatory a later owner added. Previous enlargement counts toward the allowance [S1].
Three metres of projection can still be refused by the other tests on the same page. Only half the land around the original house may be covered by extensions and other buildings [S1]. Within two metres of a boundary, the eaves height cannot exceed three metres [S1]. You cannot build forward of the principal elevation, or of a side elevation that fronts a highway [S1]. Exterior materials must be similar in appearance to the existing house [S1]. The work must not include a veranda, balcony or raised platform, or an alteration to the existing roof [S1].
Where prior approval is available, the Portal allows a longer single-storey rear extension: eight metres if detached, six metres otherwise [S1]. That route is a different application. A household that wants to stay on the ordinary three metre line should say so in the brief, or the quotes will describe a larger room.
Flats and maisonettes are not in these householder rights [S1]. Article 2(3) designated land, a Site of Special Scientific Interest in the prior-approval case, a planning condition, or an Article 4 direction can all change the answer [S1]. If the house is in Nantwich, Crewe or Sandbach, Cheshire East is the authority to ask. Do not treat a neighbour's recent extension as proof that yours is permitted.
The wider picture of side extensions, two-storey limits and the Community Infrastructure Levy warning sits on the house extension page. Price the three metre rear case on its own.
Building regulations at a modest depth
A room three metres deep is still an extension of a building. GOV.UK says you must check whether you need approval before you construct or change buildings in certain ways, and that the Building Regulations 2010 cover the construction and extension of buildings [S2]. Approval is different from planning permission [S2]. You might need both [S2].
The page also says that if you cannot decide, check with a building control body, and that you can choose the local authority's building control department or a private registered building control approver [S2]. Put that choice, and the fee, on the quote. A short projection does not answer the question for you.
GOV.UK: find your local council for building control. QuoteZila is not affiliated with this organisation.
Ground, drains and next door
The expensive unknowns at this depth are usually under the floor and along the boundary, not in the brick count. A written quote should state the foundation depth rather than leave it blank. GOV.UK says that digging near to and below a neighbour's foundations is within the Party Wall etc. Act 1996, as is new building on or at the boundary [S3]. The Act is separate from planning permission and from building regulations approval [S3].
On a terrace, three metres of new room can sit close to the shared wall. Where the Act applies, serve a party wall notice before the trench is dug. Ask each builder to say, in writing, whether they think the Act applies and whether their fee for dealing with it is included.
Manholes in the three metre strip are common. Shifting one is not "included" unless the quote says so. Ask.
What to compare when every quote says three metres
| Check | What you are looking for |
|---|---|
| Depth measured from the original rear wall | Not from a later porch or conservatory [S1] |
| House type named | Three metres is the non-detached rear cap; detached is four unless another rule applies [S1] |
| Height and distance to the boundary | Eaves within two metres of a boundary stay at or under three metres [S1] |
| Half the garden already used | Earlier buildings count [S1] |
| Foundations and drains described | Neighbour foundations can bring in the Act [S3] |
| Opening up the back wall | Forming an opening is its own building-regulations question |
| Who applies for building control | Extensions are covered [S2] |
| Shell only, or plaster, electrics and a floor | The usual missing lines |
| VAT | A business registers when taxable turnover goes over £90,000 [S5] |
What to put in the post
- "Single storey, three metres beyond the original rear wall", plus the house type.
- A tape measurement and a photo that shows both corners and any manhole.
- Whether a side passage is the only way to bring materials in.
- Whether you want the back of the house opened into the new room.
- The postcode.
Jobs you might post
These are examples, not taken from real job posts.
- "Terraced house in Crewe. Single storey, three metres from the original back wall, full width of the kitchen. Please include foundations, the steel if the back wall comes out, building control and making good. Units stay as they are."
- "Semi-detached. We measured three metres to the fence. Please say if the eaves rule near that boundary changes the design, and price only the ordinary limit, not the longer prior-approval depth."
- "Detached house. We know the ordinary rear allowance is longer than three metres. Please still price a three metre room, and say in the quote that you have not assumed the longer depth."
Reading the quotes
Citizens Advice says a quote is a fixed price and an estimate is a rough guess, and that you should collect written quotes from at least three traders [S4]. After you accept, it is a binding agreement, which is why the depth and the exclusions need to be on the paper [S4]. A much lower price can mean the work is not the same work [S4].
Ask to see insurance, and check the policy will still be in force when the job finishes [S4]. If a guarantee is offered, ask if it is insurance-backed [S4]. For money up front, keep any unavoidable deposit to no more than 25% and take a receipt [S4].
Sources to open yourself
QuoteZila is not affiliated with these organisations.
- Rear limits: Planning Portal extensions [S1].
- Building regulations: GOV.UK [S2].
- Party walls: GOV.UK [S3].
- Quotes: Citizens Advice [S4].
- VAT: GOV.UK register for VAT [S5].
This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.
Where this applies. The three metre and four metre lines are England householder rules as the Planning Portal states them. They are not a builder's rate. Outside England, ask the local planning authority before you brief anyone.
A tape measure taken from a later conservatory describes the wrong wall. Measure from the original rear of the house, and say in the post if an older extension is already there, so every quote starts from the same line.
Post a three metre extension
Name the depth, the house type and the town. Up to five matched local businesses can reply [QZ2]. QuoteZila is free for customers and local businesses [QZ1].
Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.
Posting a job is not open yet
Structural work of this kind is on the builders page. Glazing is also a glaziers question if the rear is mostly glass. All services lists other trades.
Questions about a three metre extension
How much does a 3 metre house extension cost?
The Federation of Master Builders' single-storey guide of 4 March 2026 says the UK average is between £1,800 and £3,000 per square metre, and its house extensions guide, read on 30 October 2026, gives the same £1,800 to £3,000 band. That is a rate per square metre for a single-storey extension, not a package price for a three metre room, and not a Cheshire price. Three metres remains a depth the Planning Portal uses for many houses that are not detached. Prices vary by the job and the location, and QuoteZila does not set prices.
Is three metres always allowed?
No. The Planning Portal says a single-storey rear extension must not go more than three metres beyond the rear wall of the original house if the house is not detached, or four metres if it is detached, and the height must not exceed four metres. Earlier extensions count. Flats are outside the rules. A condition or an Article 4 direction can remove the right.
Is a detached house limited to three metres as well?
The ordinary single-storey rear limit on the Planning Portal is four metres for a detached house, and three metres for any other house. A detached house can still be held to a shorter depth by a condition, by Article 2(3) land, or by the other tests, including height and the half-garden rule.
Do I still need building regulations approval at this size?
Size under a planning cap is not an exemption. GOV.UK says the Building Regulations 2010 cover the construction and extension of buildings, and that approval is different from planning permission. Ask building control even when the depth looks modest.
What if the neighbour's foundations are close?
GOV.UK says the Party Wall etc. Act 1996 covers excavation near to and below the foundation level of neighbouring buildings. A three metre room on a terrace can be that situation. Where the Act applies, use a party wall notice. The Act is separate from the planning depth.
How should a deposit be handled?
Citizens Advice says to aim not to pay a deposit, to offer to purchase materials yourself, and not to agree more than 25% if a deposit cannot be avoided. Get a receipt. Ask first if the firm charges to write the quote.
Does QuoteZila check the firms that price a small extension?
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.
Can I post this size of extension on QuoteZila?
Yes. Say three metres from the original rear wall, name the house type, and add a Cheshire postcode. Up to five matched local businesses can quote. QuoteZila is free for customers and local businesses.
Related reading
- Plumber cost: if the new room moves a sink or a radiator
- Electrician cost in Cheshire: for new circuits in the extension
- Builders
- All cost guides
Part of Cost guides. All services
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Related pages
- Asbestos removal: what the quote must say. An asbestos quote in Cheshire depends on the material, the licence question and the waste route. This guide prints no removal figure and no removal method.
- Brick Cost: What Changes the Price of Bricks. What moves the price of bricks for a wall, extension or repair: brick type, colour matching, quantity, delivery, waste, and the labour to lay them.
Sources
- QZ1: QuoteZila product fact. QuoteZila pricing line.
- QZ2: QuoteZila product fact. QuoteZila FAQ.
- S1: Planning permission: extensions, Planning Portal. Accessed 2026-10-27. https://www.planningportal.co.uk/permission/common-projects/extensions/planning-permission/
- S2: Building regulations approval, GOV.UK. Accessed 2026-10-27. https://www.gov.uk/building-regulations-approval
- S3: Party Wall etc Act 1996 guidance, GOV.UK. Accessed 2026-10-27. https://www.gov.uk/guidance/party-wall-etc-act-1996-guidance
- S4: Before you get work done on your home, Citizens Advice. Accessed 2026-10-27. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/
- S5: When to register for VAT, GOV.UK. Accessed 2026-10-27. https://www.gov.uk/register-for-vat
- S6: Single-storey extension costs, Federation of Master Builders. Accessed 2026-10-30. https://www.fmb.org.uk/resource/single-storey-extension-costs-a-practical-guide-for-homeowners.html
- S7: 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