Permitted development saves homeowners thousands when used right. It costs them tens of thousands when it isn't. The rules are precise. The penalties are real. Here's what actually applies in England, and where homeowners trip up.
How a 180-millimetre mistake cost £18,000 and nine months
The owners wanted a 4-metre kitchen extension. Their builder said it was permitted development. The plans went in for Building Regs only. Construction started in March.
Two things were missed. First, the property is a semi-detached — the limit is 3 metres, not 4. Second, even if it had been detached (4m limit), the builder set the rear wall at 4.18m to accommodate the kitchen island. By June the extension was 80% built.
A neighbour complained. The council's enforcement officer measured. The breach was confirmed. A Section 171 enforcement notice followed TCPA 1990 · s.171, requiring the rear glazing wall to be taken down and rebuilt 200mm forward of its current position.
The owners applied for retrospective planning permission. It was refused: the projection was unacceptable in relation to the neighbour's amenity. Total cost of putting it right: £11,400 in remedial works, £4,200 in consultancy and application fees, and £2,500 in extended hire and contractor delays. Nine months later the kitchen was finished.
The lesson: "permitted development" means nothing without measuring against the right starting point — the original wall of the original house — and against the right limit for the property type. Both checks take an hour. Neither was done.
01 / What it isWhat permitted development actually is
Permitted development (PD) is planning permission granted by Parliament rather than your council. It sits in one piece of secondary legislation: the Town and Country Planning (General Permitted Development) (England) Order 2015 GPDO 2015 · SI 2015/596.
Inside the GPDO are dozens of "Classes" of development. Each Class has its own size, height, siting and material conditions. Meet every condition for a Class and you can build without a planning application. Miss one — by any margin — and the work needs permission.
PD is national. Councils cannot grant it, withhold it or change the rules. They can only restrict it in defined areas using an Article 4 direction, which removes specific PD rights and forces you to apply.
02 / What it coversWhat you can build under PD
For a typical English house, the rights worth knowing live in Schedule 2, Part 1 of the GPDO:
Class A — extensions (single-storey, two-storey, side, rear).
Class B — loft conversions and roof additions.
Class C — other roof alterations (rooflights).
Class D — porches.
Class E — outbuildings and curtilage works (sheds, garden offices, summerhouses).
Class F — hard surfaces (driveways, patios).
Classes G–H — chimneys, flues, antennae.
Energy-related rights — heat pumps, solar panels, EV chargers — sit in Parts 2 and 14. PD does not apply to flats, maisonettes, or any building that isn't a single dwellinghouse.
Not sure if your project is PD? Take the free quiz.
Answer 15 questions about your property and your plans. We'll tell you in plain English whether PD applies, what to check next, and whether to apply for a Lawful Development Certificate.
Take the PlanWiser quiz03 / The numbersThe limits in numbers
The headline limits are precise. A single-storey rear extension can project 3 metres from the original rear wall on terraced and semi-detached houses, or 4 metres on detached. Maximum overall height is 4 metres. Maximum eaves height is 3 metres within 2 metres of any boundary.
The Larger Householder Development route extends single-storey rear projections to 6 metres (terraced/semi) or 8 metres (detached), but requires prior approval — including a 21-day neighbour consultation.
Two-storey rear extensions: maximum 3-metre projection. Minimum 7 metres to the rear boundary. Eaves and ridge no higher than the existing house.
Single-storey side extensions: no more than half the width of the original house. Single-storey only.
Combined extensions and outbuildings cannot cover more than 50% of the curtilage outside the original footprint GPDO Sch.2 Pt.1 Class A.1(c).
04 / Side by sidePermitted vs not permitted
Same property type, same project type, different result. The difference is millimetres.
Single-storey rear, 3m projection on a semi-detached. 3.8m overall height. Eaves at 2.9m within 1.8m of the boundary. All within Class A.
Same extension at 3.18m — 180mm too deep. Needs a planning application. Likely to be refused on the same projection that 3m would have approved.
Single-storey side extension at 4m wide on a 9m original house. Half-width or less. Single storey. Within Class A.
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. Class E.
Same garden office at 2.7m high in the same position. 200mm over the boundary height limit. Pull it forward to ≥ 2m from the boundary, or reduce height, to recover PD.
Roof solar panels projecting 180mm above the slope, below the ridge line. MCS-installed. Outside a conservation area. Class A of Part 14.
Same panels in a conservation area on a wall facing the highway. Designated land restrictions apply. Planning permission needed.
PD Calculator: check your project
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 (or since 1 July 1948 for older houses)?
05 / The trapThe "original dwellinghouse" trap
Every limit above is measured against the original dwellinghouse — the building as built, or as it stood on 1 July 1948 if older GPDO Sch.2 Pt.1, para A.1.
Previous extensions count. Including ones built decades before you bought the house. 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. Ask your solicitor for any relevant certificates. If the rights are gone, full planning permission is your only route.
Cumulative use applies to side and rear extensions combined. A previous side extension that took the wall to its limit cannot be added to without planning — even if your new project would, on its own, sit within the numbers.
06 / Other consentsPD 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.
Leasehold consent from the freeholder is required if you don't own the freehold. Catches owners of leasehold houses, not just flats.
07 / Energy worksHeat pumps, solar and EV chargers
The energy-transition PD rights changed materially in 2023 and 2024.
Air-source heat pumps qualify on most domestic properties subject to MCS-certified installation, noise conditions and a 1.5m³ volume cap. The previous one-metre boundary rule has been relaxed in many cases GPDO Sch.2 Pt.14, Class G.
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). EV chargers are PD under Class D of Part 2, subject to height and street-facing limits.
Listed buildings, conservation area front elevations and properties subject to active Article 4 directions are the main exceptions.
08 / RefusalsFive common reasons prior approval gets refused
Standard PD 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 I see:
Loss of light to a neighbour's main living window
The 45-degree rule and BRE daylight tests apply. A 6m or 8m extension projecting past a neighbour's ground-floor habitable window almost always fails this test. Councils receive an objection, run the test, and refuse.
Overbearing / "tunnel effect" between properties
Where two adjoining properties both extend, or where a single 8m extension creates a wall that dominates the neighbour's garden, councils refuse on amenity. Most common where rear gardens are below 12m deep.
Notification not served on all attached neighbours
Larger Householder requires written notice to every owner or occupier of premises sharing a wall or fence with your property. Miss one and the application is invalid — refused on procedural grounds without an amenity assessment.
Property in an area with PD removed
If an Article 4 direction has removed the Class A right at your address, prior approval doesn't apply at all — full planning permission is required. Easy to miss because Article 4s are poorly publicised.
Curtilage already at or near 50%
Where previous extensions and outbuildings already occupy close to half the curtilage, a Larger Householder addition pushes the property over the limit. PD doesn't apply at all.
09 / Bottom lineWhat this means for your project
PD looks like a shortcut. It's a tightly drafted exemption with a long list of ways to lose it. The numbers matter to the millimetre. Cumulative use matters more than most homeowners realise. And PD never replaces Building Regulations, Party Wall notices, restrictive covenants or freeholder consent.
If a project is genuinely within scope, the time and cost saved is real. If it's borderline, an application for a Lawful Development Certificate before you build is the cheapest insurance you'll buy: £129, eight weeks, written confirmation.
