What is permitted development and what are its limits?
Permitted Development
The rules that let you extend without planning permission — and the limits that catch more homeowners out than you'd expect.
A couple in Hertfordshire extended their kitchen by 4.3 metres. Their detached house was entitled to 4m under permitted development. The extra 300mm — a single brick's depth beyond what they thought was the boundary of the original building — cost them £18,000 in retrospective planning fees, amended drawings, neighbour compensation, and delay. The extension itself was fine. The planning position was not.
Permitted development is not a grey area. It is a set of precise numerical thresholds. Stay inside them and you need no planning application. Exceed them by any amount and the work is unauthorised. This guide explains what PD covers, where the limits are, and — critically — why so many homeowners get it wrong.
What permitted development actually is
Permitted development rights are a statutory grant of planning permission made by Parliament through the Town and Country Planning (General Permitted Development) (England) Order 2015 GPDO 2015. They allow specific classes of development without requiring a planning application to the local authority. The council has no discretion to refuse — if the conditions in the GPDO are met, the development is lawful.
That is also the trap. PD is conditional and absolute simultaneously. Conditional in that every size, height, and siting requirement in Schedule 2 must be satisfied. Absolute in that exceeding any single condition by any amount removes the right entirely — there is no "nearly permitted development." The same council that could not refuse a compliant scheme cannot approve a non-compliant one under the PD route.
Two further concepts matter from the start.
- Prior approval
- A halfway step for specific classes of PD. Larger Householder rear extensions (6m–8m), some change-of-use conversions, and other classes require the council to be notified and given a fixed period to assess particular impacts. Lighter than a full application — but not no-permission.
- Lawful Development Certificate (LDC)
- A written formal confirmation from the council that a proposed or existing development is lawful. Not legally required to build under PD, but strongly recommended: it is the document that satisfies buyers' solicitors, mortgage lenders, and building insurers. The fee is £274 for proposed use, and the council has eight weeks to respond TCPA 1990, s.191–192.
The limits in numbers
Schedule 2 of the GPDO 2015 sets out the classes. The most relevant for householders are:
Class A — extensions and alterations: single-storey rear extensions up to 4m (detached) or 3m (terraced and semi-detached), with a maximum height of 4m overall and 3m eaves within 2m of a boundary. Two-storey rear extensions up to 3m, with the rear boundary at least 7m from the original rear wall. Side extensions up to half the width of the original house, single storey only. Materials must be similar in appearance to the existing dwelling.
Class A (Larger Householder — prior approval): single-storey rear projections from 4m to 8m (detached) or 3m to 6m (semi and terraced). Requires a written notification to the council and a 42-day neighbour consultation window. The council can refuse on amenity grounds.
Class B — loft additions: cumulative additions of up to 50m³ (detached and semi-detached) or 40m³ (terraced). No front dormers. No materials extending beyond the plane of the existing roof slope facing the highway. Not permitted in designated land GPDO 2015, Sch.2 Pt.1 Class B.
Class E — outbuildings: garden offices, sheds, and summerhouses within the curtilage, not forward of the principal elevation. Maximum eaves height 2.5m within 2m of any boundary. Combined with extensions, the total cannot exceed 50% of the original curtilage.
Limits by project type — England, June 2026
| Project type | Detached | Semi / Terrace | Key conditions |
|---|---|---|---|
| Rear (single-storey)Class A standard PD | 4m | 3m | Max 4m overall height; max 3m eaves within 2m of boundary; similar materials |
| Rear (Larger Householder)Prior approval required | 8m | 6m | 42-day neighbour consultation; council can refuse on amenity grounds |
| Rear (two-storey)Class A standard PD | 3m | 3m | Min 7m to rear boundary; eaves and ridge no higher than existing house |
| Side (single-storey)Class A — 2-storey not PD | ½ width | ½ width | Not permitted in designated land; not PD in conservation areas or AONBs |
| Loft additionClass B — cumulative | 50m³ | 40m³ | No front dormers; not permitted in designated land; prior additions count |
| OutbuildingClass E | 50% curtilage | 50% curtilage | Max 2.5m eaves within 2m of boundary; not forward of principal elevation |
Permitted vs not permitted: side-by-side examples
3m rear extension on a semi-detached house. Exactly at the Class A limit. Materials match the host dwelling. No previous extensions.
3.1m rear extension on a semi-detached house. 100mm over the limit. Full planning application required regardless of how small the excess is.
Single-storey side extension, 3m wide, on a house with a 6.5m original width. Within the half-width rule. No previous side extensions.
Same width but two storeys. Side extensions of two or more storeys are excluded from PD entirely. Full planning needed.
Garden office, 4m × 3m, 2.4m high, sited 1.5m from the rear boundary. Below the 2.5m height threshold within 2m of a boundary.
Same garden office at 2.7m high in the same position. 200mm over the boundary-height limit. Move it to ≥2m from the boundary, or reduce height, to recover PD.
PD calculator: check your project in 60 seconds
Check whether your project is likely permitted development
Four questions. We tell you whether your project is likely permitted development, needs prior approval, or needs full planning permission.
What kind of property are you working on?
Is the property in any of these designated areas?
What do you want to build?
Has the house been extended since it was originally built?
The "original dwellinghouse" trap
Every limit in the GPDO is measured against the original dwellinghouse — the building as built, or as it stood on 1 July 1948 if older GPDO 2015, Sch.2 Pt.1, para A.1. Previous extensions count — including ones built decades before you bought the house and never recorded in the planning register because they were also PD.
A 1930s semi might have a conservatory from 1992, a kitchen extension from 2007, and a side return from 2018, leaving zero PD rights remaining today. Most homeowners never check. Before designing anything: pull the planning history from your council's online register, look at historic Ordnance Survey maps, and ask your solicitor for any relevant certificates.
PD is not permission for everything else
Permitted development settles one question only: do you need a planning application? Four other consent regimes operate alongside it, and almost always still apply.
Building Regulations approval is required for nearly every extension, loft conversion, and structural change. Separate from planning. Always.
The Party Wall etc. Act 1996 applies if you're building on, against, or within 3–6 metres of a shared structure or boundary.
Restrictive covenants on your title can prohibit work that PD permits. There is no override — the covenant binds future owners and cannot be removed by the council.
Leasehold consent from the freeholder is required if you don't own the freehold. This catches owners of leasehold houses, not just flat owners.
Heat pumps, solar panels and EV chargers
The energy-transition PD rights changed materially in 2023.
Air-source heat pumps qualify on most domestic properties under Class G of Part 14 of the GPDO, subject to MCS-certified installation, a 1.5m³ volume cap, and noise conditions. The 2023 amendments removed the previous one-metre boundary rule in many cases GPDO 2015, Sch.2 Pt.14, Class G. Listed buildings are excluded entirely. In conservation areas, units cannot be on any elevation or slope facing a highway.
Roof-mounted solar panels are PD if they project no more than 200mm above the roof slope and don't sit higher than the ridge (excluding chimneys). In conservation areas, AONBs and National Parks, panels cannot be on a wall or slope facing a highway.
EV chargers are PD under Class D of Part 2, subject to a 0.2m³ volume cap and a maximum height of 1.6m above ground. Conservation area front-elevation restrictions apply here too.
Five common reasons prior approval gets refused
Standard permitted development doesn't get "refused" — it either applies or it doesn't. But the Larger Householder route (6m and 8m rear extensions) requires prior approval, and councils do refuse it. The five most common grounds:
How this advice is generated
Statutory facts cited to primary legislation. Practical guidance draws on Tom Weighton's experience assessing householder applications at local planning authorities and in private consultancy. The Hertfordshire case is a genuine client matter with altered identifying details. Drafting assisted by AI tools, then fact-checked and reviewed by an MRTPI before publication.
Data sources
- GPDO 2015, Schedule 2 — dimensional limits and class conditions
- TCPA 1990, ss.171–172 — enforcement notices
- Levelling-up and Regeneration Act 2023, s.115 — 10-year enforcement limit
- MHCLG technical guidance on permitted development for householders
- England householder fee schedule (current as of 1 April 2026)
Limitations of this guidance
- England only — Scotland, Wales and Northern Ireland have separate PD regimes.
- General guidance only — not planning advice for a specific property.
- PD is fact-sensitive: the same project can be lawful on one house and unlawful on its neighbour.
- Rights and fees change — this page is reviewed when the GPDO or national fee schedule is amended.
- Always confirm your position with your LPA or apply for a Lawful Development Certificate before building.
Frequently asked questions
What's the difference between planning permission and permitted development?
Planning permission is granted case-by-case by your local planning authority. You submit an application, pay a fee (£548 for a householder application in England from 1 April 2026), and wait through an 8-week determination. Permitted development is granted in advance, by Parliament, through the GPDO 2015. No application. No fee. No decision.
Two qualifications matter. Prior approval is a halfway step: certain PD rights — Larger Householder rear extensions of 6 to 8 metres — require you to notify the council and let them assess specific impacts before you start. Lighter than full planning. Not no-permission. PD is conditional and absolute simultaneously. Conditional in that every numerical limit must be met. Absolute in that the council has no discretion to vary the rules. If you're unsure your project meets the conditions, apply for a Lawful Development Certificate (£274). Written confirmation. Buyers' solicitors will request it on sale. Take the PlanWiser quiz at planwiser.uk/take-the-assessment to see whether your project is PD.
How big can I extend my house without planning permission?
Single-storey rear extensions: 3m projection on terraced and semi-detached, 4m on detached. Maximum overall height 4m. Maximum eaves 3m within 2m of any boundary. Two-storey rear: 3m projection. Minimum 7m to the rear boundary. Eaves and ridge no higher than the existing house. Single-storey side: half the original house width, single storey only.
The Larger Householder Development route extends single-storey rear projections to 6m (terraced/semi) or 8m (detached), but requires prior approval — including a 42-day neighbour consultation. The council can refuse on amenity grounds.
Three traps. First, "original" means the house as built (or as it stood on 1 July 1948 if older), not as it stands today — previous extensions count. Second, combined extensions and outbuildings cannot cover more than 50% of the curtilage outside the original footprint. Third, designated areas (conservation areas, AONBs, National Parks) impose stricter limits. Use PlanWiser's quiz at planwiser.uk/take-the-assessment to confirm your specific limits.
Can I install a heat pump under permitted development?
Yes, in most cases. Air-source heat pumps qualify under Class G of Part 14 of the GPDO 2015, provided installation meets MCS standards, the unit's volume is below 1.5 cubic metres, and noise conditions are met. The 2023 amendments removed the previous one-metre boundary restriction in many cases.
Ground-source heat pumps face fewer restrictions when sited within domestic curtilage.
Three exclusions. Listed buildings are excluded entirely — listed building consent is required. In conservation areas and other designated land, units cannot be on the principal elevation or any wall facing a highway. Article 4 directions in some local areas restrict heat pump PD. The MCS certificate is the document that proves PD compliance. Keep it — buyers' solicitors will ask for it on sale.
How do I know if my permitted development rights have already been used up?
Three checks before you design anything. First, search your local planning authority's online application register for your address. Every previous planning application, certificate of lawfulness and prior approval is listed there. Note that PD work may not appear in the register at all — it didn't need an application.
Second, look at historic mapping. The National Library of Scotland's georeferenced OS maps let you compare your house's footprint across decades. If the building has visibly grown since the 1948 baseline, those additions count against your current allowances.
Third, ask. On purchase, ask explicitly: "Have any extensions been built under permitted development, and what allowance is left?" If you suspect rights are gone, applying for a Lawful Development Certificate (£274) before you build is the only safe answer. The council either confirms you have rights or tells you that you don't. Take the PlanWiser quiz at planwiser.uk/take-the-assessment to scope your position.
What happens if I exceed permitted development limits?
The work becomes unauthorised. Three things follow. First, the council can serve an enforcement notice under the Town and Country Planning Act 1990, requiring the breach to be remedied — typically by alteration or removal. Failure to comply is a criminal offence. The Levelling-up and Regeneration Act 2023 extended enforcement immunity from four years to ten years for most operational breaches, in force from 25 April 2024 take the PlanWiser quiz to understand your risk.
Second, you can apply for retrospective planning permission — there is no guarantee it will be granted. Refusal is common where the breach is significant or affects neighbours.
Third, the breach surfaces at sale. Buyers' solicitors flag any open enforcement matter and any work that lacks a Lawful Development Certificate where one would normally exist. A sale can collapse, indemnity insurance may be required, or the buyer's lender may withdraw. The cost of getting it wrong substantially exceeds the cost of getting it right. An LDC costs £274 and takes around eight weeks.
Permitted development is not a get-out-of-planning-jail-free card. It is a set of precisely drafted statutory rights that save real time and money when the conditions are met — and create real legal and financial problems when they are not. The limits are binary, the cumulative rules catch more homeowners than any other single issue, and PD never replaces the four other consent regimes that run in parallel. If you are unsure, the Lawful Development Certificate is the cheapest certainty money can buy.
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Book the sessionHow this guide was researched
All statutory facts cited to primary legislation. Practical ranges drawn from Tom Weighton's practice experience and official guidance. England only. Subject to legislative change. Updated June 2026.
Sources
- Town and Country Planning (General Permitted Development) (England) Order 2015 — legislation.gov.uk
- Permitted development rights for householders: technical guidance — MHCLG
- Planning Practice Guidance: When is permission required? — gov.uk
- Town and Country Planning Act 1990 — legislation.gov.uk
- Levelling-up and Regeneration Act 2023 — legislation.gov.uk
- National Planning Policy Framework, December 2024 — gov.uk
