Most single-storey rear extensions in England do not require planning permission. They fall under Permitted Development (PD) rights, a pre-approved consent that lets homeowners build within defined dimensional limits without a formal application. The moment an extension exceeds those limits, or the property falls into an excluded category, you need either Prior Approval or a full planning application.1

This article covers PD size limits, the extended Prior Approval route, when full permission is required, Lawful Development Certificates, and the separate party wall process, all figures are for England in 2026.

Scotland, Wales and Northern Ireland have separate planning regimes and are not covered here.

Permitted Development Rights: What They Are and Where They Come From

Permitted Development rights for house extensions derive from Schedule 2, Part 1, Class A of the Town and Country Planning (General Permitted Development) (England) Order 2015 (GPDO). They are attached to the property, not the owner, and can be removed by an Article 4 Direction (a local authority instruction) or by a planning condition on the original consent, common on new-build estates. Always check your title register or call the local planning authority before assuming PD applies.2

Where PD rights do not apply

  • Flats and maisonettes, no Class A PD rights; any extension needs full permission
  • Listed buildings, PD suspended; Listed Building Consent also required
  • Conservation Areas, National Parks, AONB, the Broads and World Heritage Sites (“article 2(3) land”), reduced PD: side extensions, two-storey rear extensions and external cladding are excluded, and the larger home extension route is not available2
  • Article 4 Direction areas, local authority has removed PD (common in some London boroughs)
  • Planning condition on original consent, check the decision notice for your property

Single-Storey Rear Extension: PD Size Limits

For the majority of houses in England not caught by the exclusions above, a single-storey rear extension is PD if it satisfies all of the following simultaneously:

ParameterDetached houseSemi-detached / Terraced
Maximum depth from original rear wall4 m3 m
Maximum eaves heightNo higher than the existing eavesNo higher than the existing eaves
Maximum overall height4 m4 m
Eaves height within 2 m of boundary3 m max3 m max
Ground covered by buildings other than the original house50% of the curtilage50% of the curtilage

The eaves of the extension may be no higher than the eaves of the existing house, and within 2 m of a boundary they may be no higher than 3 m.2

Depth is measured from the original rear wall of the dwelling, meaning the wall as it existed when the house was built, or as it stood on 1 July 1948 for older properties.3 If a previous owner already extended 2 m into the garden, you only have 1 m of PD depth left on a semi-detached, not 3 m. The GPDO measures cumulative extensions, not just the current proposal.1

Additional conditions that must all be met:

  • The extension must not extend beyond the front wall (principal elevation) of the house at any point
  • It must not include a raised platform, balcony, or veranda, a standard ground-level patio is fine; a decked platform over 300 mm above ground is not PD1
  • Materials must be of similar appearance to the existing house, matching brick, render, or roofing material2
  • Roof lights added to the roof of the main house fall under a separate class (Class C) and must not protrude more than 150 mm beyond the plane of the original roof slope1

Two-Storey and Upper-Floor Extensions

Two-storey rear extensions are permitted development under stricter limits:

  • Maximum depth: 3 m (all house types)2
  • Must be at least 7 m from the rear boundary (the boundary opposite the rear wall of the house)2
  • The roof pitch must match the main house as far as practicable2
  • Any upper-floor window in a side elevation must be obscure-glazed, and non-opening unless the opening parts are more than 1.7 m above the floor of the room2

Side extensions are PD only if single storey, with a maximum width of 50% of the original house width and a maximum height of 4 m.2 On article 2(3) land (which includes National Parks, AONB and Conservation Areas), side extensions are not permitted development at all, even single storey.2

The Larger Home Extension Scheme (Prior Approval)

Since 25 May 2019, when a temporary scheme was made permanent, the Neighbour Consultation Scheme (the larger home extension route under Class A) has allowed single-storey rear extensions up to double the standard PD limits, subject to a formal Prior Approval process and only on houses that are not on article 2(3) land or a site of special scientific interest:24

House typeMaximum depth under Larger Home Extension
Detached house8 m
Semi-detached house6 m
Terraced house6 m

Height limits remain the same as standard PD (4 m overall, 3 m eaves within 2 m of boundary).2

How the Prior Approval process works

Submit a Prior Approval application via the Planning Portal (fee: £249).5 The council writes to immediately adjoining neighbours, who have 21 days to comment.2 If no objections arrive, or if the council considers any objections do not demonstrate unacceptable amenity impact, Prior Approval is granted. Silence from the council after 42 days from submission is automatically treated as approved.2 The council can only assess neighbour amenity impact; it cannot refuse on design or appearance grounds.2 If refused, you can appeal to the Planning Inspectorate or fall back to the standard PD limits at no further cost.

When You Need Full Planning Permission

A full householder planning application is required when any of the following apply:

  • Extension exceeds PD or Larger Home Extension size limits
  • Property is a flat, maisonette, or listed building
  • The extension would sit forward of the principal elevation, or the house is on article 2(3) land (such as a Conservation Area) and the extension is to the side or is a two-storey rear extension2
  • Article 4 Direction in force, or PD removed by planning condition
  • Extension includes a balcony, raised platform, or veranda
  • Extension would take total outbuilding coverage over 50% of the curtilage

Householder application: costs and timescales

ItemDetail
Application fee (England, from April 2026)£5486
Target decision period8 weeks
Longer decision periodOnly if you agree an extension of time in writing
Planning permission validity3 years from date of decision
Appeal deadline if refused12 weeks from decision date

The council has 8 weeks to decide a householder application unless you agree a longer period in writing.78 A refused householder application can be appealed for up to 12 weeks from the date on the decision letter.9

Submit via the Planning Portal (planningportal.co.uk). Required documents typically include a site location plan (usually at 1:1250 or 1:2500), a block plan (often at 1:500 or 1:200), and existing/proposed floor plans and elevations at 1:50 or 1:100.10

Lawful Development Certificates

Even when an extension is clearly permitted development and needs no planning application, it is strongly recommended to apply for a Lawful Development Certificate (LDC) before or shortly after the work is completed.11

An LDC is a formal legal document issued by the council confirming that the works were lawful at the time they were carried out. It does not grant permission, it records that no permission was needed.

  • Fee in England: £274 from 1 April 2026 for a certificate for proposed development (half the £548 householder application fee); a certificate for existing development costs the full £548.5
  • Determination period: 8 weeks (same as full planning)12
  • Apply via: Planning Portal, as an application for a Certificate of Lawful Proposed Use or Development (CLPUD) before work, or Certificate of Lawful Existing Use or Development (CLEUD) after

Without an LDC you are relying on the PD argument holding up if challenged on sale or remortgage. A buyer’s solicitor will often ask for one on an extended property, so it is worth obtaining before you sell.

Party Wall: Separate from Planning, Often Concurrent

Planning permission and the Party Wall etc. Act 1996 are entirely separate legal frameworks, you can need both, one, or neither. They run in parallel.13

The Party Wall Act catches many rear extensions via three routes: Section 6 (excavating within 3 m of a neighbour’s foundations and deeper than them, or within 6 m where the work cuts a line drawn down at 45 degrees from the bottom of those foundations, which between them catch many extensions built near a neighbouring building); Section 1 (building on or at the boundary line); and Section 2 (work on a shared party wall, such as cutting away a projecting chimney breast).14

Party wall procedure in brief

Serve written notice on affected adjoining owners at least 2 months before work begins for a section 3 party structure notice, or at least 1 month before for a section 1 line of junction notice or a section 6 excavation notice.1315 Neighbours have 14 days to respond. Written consent means no surveyor is needed. If they dissent, fail to respond, or do not reply within 14 days, a dispute is deemed to have arisen and both parties appoint surveyors (or agree on a single surveyor) to settle a Party Wall Award.16 The building owner typically pays both surveyors’ fees: allow £700–£1,500 per owner in the South East. The whole process adds 1–3 months to the pre-construction programme and is the most common cause of delayed starts on otherwise straightforward extensions.

Quick-Reference Planning Route Table

Extension typeTypical planning routeKey size limitFee
Single-storey rear, within standard limitsPermitted Development, no application4 m depth (detached); 3 m (semi/terrace)£0 (LDC recommended at £274)
Single-storey rear, 4–8 m / 3–6 m depthPrior Approval (Larger Home Extension)8 m (detached); 6 m (semi/terrace)£249
Two-storey rear, within PD limitsPermitted Development, no application3 m depth; 7 m from rear boundary£0 (LDC recommended at £274)
Side extension (single storey, within limits)Permitted Development, no application50% of original house width; 4 m high£0
Any extension on a flat or maisonetteFull planning permission requiredNo PD rights, any size£548
Extension on a listed buildingFull planning permission + Listed Building ConsentAny size£548 + £0 (LBC has no fee)
Extension exceeding PD/Prior Approval limitsFull planning permission requiredAny size£548

Frequently Asked Questions

Do I need Building Regulations approval even if my extension is permitted development?

Yes, always. Planning and Building Regulations are completely separate. The extension of a building is building work under the Building Regulations, so almost every extension needs approval (small ground-floor porches and conservatories are the main exemptions), either via a Full Plans application to building control before work starts, or a Building Notice.17 PD status has no bearing on this.

Can my neighbour block my extension?

Not through the planning system for standard PD, there is no public consultation. Under the Larger Home Extension Prior Approval route, neighbours can object and the council may refuse on amenity grounds. Under the Party Wall Act, neighbours can trigger a surveyor process that delays the start by 1–3 months, but cannot ultimately veto lawful works; the Party Wall Award sets conditions, not a right of refusal.

How long is planning permission valid?

Three years from the date of the decision notice.18 You must start a material operation within that period; completion afterwards is fine.

I built an extension without checking, what now?

Establish whether the extension was PD at the time it was built. If it was, apply for a retrospective LDC (CLEUD, Certificate of Lawful Existing Use or Development). If it genuinely required planning permission, apply retrospectively, councils can and do grant it. The risk of doing nothing is an enforcement notice: in England councils now have 10 years from substantial completion to take enforcement action against unauthorised building work (the old 4-year limit applies only to work substantially completed before 25 April 2024).19 Enforcement notices can require demolition, so regularise early.

References (19)

Figures in this note were checked against the sources below on 30 September 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

  1. 1technicalvery strongThe National Archives, legislation.RN-OWGIY3Schedule 2 Part 1 of the GPDO 2015, development within the curtilage of a dwellinghouse. This is permitted development itself: Class A enlargement and alteration, with the limits and conditions, through the classes covering roof alterations, porches, outbuildings and hard surfaces. Every statement about what can be built without planning permission traces to this Part, and the exclusions at the start of each class are where most projects actually fall out.
  2. 2technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-Z0XQ8VParagraph A.1 sets the householder extension limits: buildings may not cover more than 50 per cent of the curtilage (A.1(b)); a single-storey rear extension may not extend more than 4 metres beyond the rear wall of a detached house or 3 metres for any other house, nor exceed 4 metres in height (A.1(f)), rising to 8 metres and 6 metres under the larger home extension route (A.1(g)); an extension of more than one storey may not extend more than 3 metres beyond the rear wall or be within 7 metres of the rear boundary (A.1(h)); eaves within 2 metres of a boundary may not exceed 3 metres (A.1(i)); a side extension may not exceed 4 metres in height, have more than one storey or be wider than half the width of the original house (A.1(j)). Paragraph A.2 removes cladding and side or multi-storey rear extensions on article 2(3) land such as conservation areas. A.3 requires materials of similar appearance and obscure-glazed, non-opening upper-floor side windows unless the opening part is more than 1.7 metres above the floor, and A.4 sets the neighbour consultation (prior approval) procedure with its 42-day determination period.
  3. 3technicalvery strongThe National Archives, guidance.RN-EZ53YYArticle 2 of the GPDO defines dwellinghouse for Part 1; the definition excludes buildings containing flats and the flats within them.
  4. 4technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-YFQLLBSI 2019/907, in force 25 May 2019. Regulation 4 makes permanent the previously temporary right in Class A of Part 1 of Schedule 2 to the GPDO 2015 to enlarge a dwellinghouse by up to 8 metres for a detached dwellinghouse and 6 metres for any other dwellinghouse, by removing the time limiting date of 30 May 2019 and the conditions that required the development to be completed by that date. This is the instrument that settles the date of the larger home extension scheme: the right dates from 2013 as a temporary measure and became permanent on 25 May 2019, not in 2020. The Regulations also make amendments on advertisement consent and compensation. England only.
  5. 5technicalvery strongMinistry of Housing, Communities and Local Government (GOV.UK), a government page.RN-JM9I1NThe schedule of planning application fees in England from 1 April 2026. Fees rise annually with the September CPI under the 2023 amendment regulations; September 2025 CPI was 3.8%, so every fee from April 2025 rose by that and is charged from 1 April 2026. The table lists the new amount for each application type, which is the statutory figure a council must charge rather than a guide price.
  6. 6costvery strongPlanning Portal, guidance.RN-M2KUCTA price, true at 2026-04. The Planning Portal's consolidated guide to planning application fees in England from 1 April 2026, built from the 2012 fees regulations as amended and MHCLG's annual indexation. More usable than the regulations themselves because it puts each application type next to its current fee and its definition. The statutory amounts are in the regulations; this is the readable index to them.
  7. 7technicalvery strongMinistry of Housing, Communities and Local Government, guidance.RN-RC9BKDPlanning Practice Guidance on how a council determines an application: the statutory determination periods of 8 weeks for most householder and minor applications and 13 weeks for major ones, extensions of time by agreement, and what happens when the period passes without a decision. This is the source for how long a planning application actually takes and what recourse there is when it takes longer.
  8. 8technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-4MVF6QThe determination periods behind every 'the council has 8 weeks' claim, in the legal text rather than a council summary. Article 34(2)(a): 13 weeks from the day after receipt for an application for major development. 34(2)(aa): 10 weeks for technical details consent for major development or for public infrastructure development. 34(2)(b): 8 weeks for development which is not major development. 34(2)(bb): 5 weeks for technical details consent which is not major development. 34(2)(c): any extended period agreed in writing between applicant and authority, unless notice of appeal has already been given. Note that article 34 contains no 16-week EIA period: that substitution is made by regulation 68(2) of the EIA Regulations 2017. Article 34(9) sets the 21-day and 14-day publicity waits before determination, and 34(9A) extends both to 30 days for an EIA application accompanied by an environmental statement.
  9. 9technicalvery strongGOV.UK, guidance.RN-MA9MDEGOV.UK guidance for householder planning appeals, which sets a 12-week deadline from the decision letter (28 days where an enforcement notice has been served).
  10. 10technicalvery strongMinistry of Housing, Communities and Local Government, guidance.RN-G5VBDSPlanning Practice Guidance on making a planning application: what a valid application must contain, the national and local validation requirements, pre-application advice, and what happens when a council says an application is invalid. The source for why an application can sit for weeks without the clock starting.
  11. 11technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-3YX7QWSection 192(1) lets any person apply to the local planning authority to determine whether a proposed use of buildings or land, or operations proposed to be carried out in, on, over or under land, would be lawful. Under section 192(2) the authority must issue a certificate if the information satisfies them that the use or operations would be lawful if instituted or begun at the time of the application and must otherwise refuse; the certificate must specify the land, describe the use or operations, give the reasons and state the application date (192(3)). Section 192(4) provides that the lawfulness of any use or operations for which a certificate is in force is conclusively presumed unless there is a material change in the relevant matters before the use is instituted or the operations begun.
  12. 12technicalvery strongThe National Archives, guidance.RN-ZRVGWJthe period a local planning authority has to determine an application for a certificate of lawfulness
  13. 13technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-QBUTY2The exact wording of the two excavation triggers that decide whether a basement or a deep foundation needs a party wall notice, worth quoting rather than paraphrasing. Section 6(1) applies where the building owner proposes to excavate, or excavate for and erect a building or structure, within a distance of 3 metres measured horizontally from any part of a building or structure of an adjoining owner, and the excavation will within those 3 metres extend to a lower level than the level of the bottom of the neighbour's foundations. Section 6(2) applies within 6 metres measured horizontally where the work will within those 6 metres meet a plane drawn downwards in the direction of the excavation at an angle of 45 degrees to the horizontal. Section 6(5) requires the building owner to serve notice on the adjoining owner at least one month before beginning to excavate. Section 6(7) provides that if the adjoining owner does not serve a notice indicating consent within 14 days, they are deemed to have dissented and a dispute has arisen, which is what triggers the surveyor and award process.
  14. 14technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-WKDENHSection 2(2) lists the building owner's rights over a party structure: (a) underpin, thicken or raise; (b) make good, repair or rebuild a defective party structure; (c) to (e) demolish and rebuild non-conforming partitions, connected buildings and party structures of insufficient strength or height; (f) to cut into a party structure for any purpose, which may include inserting a damp proof course; (g) to cut away a footing, projecting chimney breast, jamb, flue or other projection to enable a wall to be built; (h) to cut away overhanging parts of an adjoining building; (j) insert flashings; (k) execute incidental works; (l) raise or rebuild a party fence wall; (m) reduce wall heights; (n) expose a previously enclosed party wall. Paragraph (f) is the one that catches chasing or breaking through a shared wall for pipework, which makes it party wall work requiring a party structure notice.
  15. 15technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-C6XFB7A party structure notice must be served at least two months before the date on which the proposed work will begin, and must state the building owner's name and address, the nature and particulars of the proposed work (with plans, sections and load particulars where special foundations are proposed) and the date the work will begin. The notice ceases to have effect if the work has not begun within twelve months of service or is not then prosecuted with due diligence. Two months for a party structure notice against one month for a section 6 excavation notice is the distinction to cite.
  16. 16technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-J0QCZGSection 5 of the Party Wall etc. Act 1996: if an owner served with a party structure notice does not serve a notice consenting within fourteen days, they are deemed to have dissented and a dispute is deemed to have arisen. The provision that makes silence a dispute, which is why a neighbour ignoring the notice triggers the surveyor process rather than allowing the work to proceed unopposed.
  17. 17technicalvery strongThe National Archives, legislation.RN-ZCMRHVRegulation 3 of the Building Regulations 2010, the meaning of building work. Lists what counts: erecting or extending a building, providing or extending a controlled service or fitting, material alteration, work required by a material change of use, and inserting insulation into a cavity wall. If a job is not on this list it is not building work, so this is the first place to check whether approval is needed at all.
  18. 18technicalvery strongThe National Archives, guidance.RN-JEP7ZHSection 91 of the Town and Country Planning Act 1990: in England development must begin within three years of the grant of planning permission unless the permission says otherwise.
  19. 19technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-Y7DV4KSection 171B(1): in England no enforcement action may be taken in respect of operations after ten years beginning with the date on which the operations were substantially completed (four years in Wales). Section 171B(2) applies the same ten-year limit in England (four years in Wales) to a change of use of a building to a single dwellinghouse, and section 171B(3) gives ten years from the date of the breach for any other breach of planning control. The England limits were extended from four to ten years by section 115 of the Levelling-up and Regeneration Act 2023, in force from 25 April 2024.

  1. The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1, The National Archives, accessed 14 September 2026. legislation.gov.uk

  2. The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1, Class A, The National Archives, accessed 14 September 2026. legislation.gov.uk

  3. The Town and Country Planning (General Permitted Development) (England) Order 2015, article 2: Interpretation, The National Archives, accessed 30 September 2026. legislation.gov.uk

  4. The Town and Country Planning (Permitted Development, Advertisement and Compensation Amendments) (England) Regulations 2019, The National Archives, accessed 30 September 2026. legislation.gov.uk

  5. Fees for planning applications in England from 1 April 2026, Ministry of Housing, Communities and Local Government (GOV.UK), accessed 7 September 2026. assets.publishing.service.gov.uk

  6. A guide to fees for Planning Applications in England, 1 April 2026, V2026, Planning Portal, accessed 15 September 2026. Priced at 2026-04, so no calibration is needed. ecab.planningportal.co.uk

  7. Determining a planning application, Ministry of Housing, Communities and Local Government, accessed 30 September 2026. gov.uk

  8. The Town and Country Planning (Development Management Procedure) (England) Order 2015, article 34: Time periods for decision, The National Archives, accessed 30 September 2026. legislation.gov.uk

  9. Appeal against a householder planning decision: how long you have to appeal, GOV.UK, accessed 30 September 2026. gov.uk

  10. Making an application, Ministry of Housing, Communities and Local Government, accessed 30 September 2026. gov.uk

  11. Town and Country Planning Act 1990, section 192: Certificate of lawfulness of proposed use or development, The National Archives, accessed 14 September 2026. legislation.gov.uk

  12. The Town and Country Planning (Development Management Procedure) (England) Order 2015, article 39: Certificates of lawful use or development, The National Archives, accessed 30 September 2026. legislation.gov.uk

  13. Party Wall etc. Act 1996, section 6: Adjacent excavation and construction, The National Archives, accessed 14 September 2026. legislation.gov.uk

  14. Party Wall etc. Act 1996, section 2: Repair etc. of party wall: rights of owner, The National Archives, accessed 30 September 2026. legislation.gov.uk

  15. Party Wall etc. Act 1996, section 3: Party structure notices, The National Archives, accessed 30 September 2026. legislation.gov.uk

  16. Party Wall etc. Act 1996, section 5: Disputes arising under sections 3 and 4, The National Archives, accessed 30 September 2026. legislation.gov.uk

  17. The Building Regulations 2010, regulation 3: Meaning of building work, The National Archives, accessed 30 September 2026. legislation.gov.uk

  18. Town and Country Planning Act 1990, section 91: General condition limiting duration of planning permission, The National Archives, accessed 30 September 2026. legislation.gov.uk

  19. Town and Country Planning Act 1990, section 171B: Time limits, The National Archives, accessed 30 September 2026. legislation.gov.uk