Extensions
Side return and wraparound extensions in London: when you need planning permission
A side infill beside a terrace's outrigger can sometimes be built as permitted development. Wrap it around the back of the house and the rules usually change, because the side and rear parts are judged as one extension. With officer decisions from 31 October and higher planning fees proposed from 8 December, it pays to check the route first.
Filling the narrow side return beside a Victorian or Edwardian terrace, or wrapping a single-storey extension around the back and side of a house, is a common way for London homeowners to add kitchen space. Whether it needs planning permission turns on a detail that catches many people out: under the permitted development rules, the side and rear parts of a joined extension are assessed together. This article is general information, not legal advice.
Side return, infill or wraparound?
These are industry terms, not legal ones. A side return is the strip of land beside the rear outrigger, the narrower back addition found on many terraced houses, and a side infill builds over it. A wraparound or L-shaped extension also extends beyond the rear wall, so it projects from both a side wall and a rear wall. What matters in planning law is which walls of the original house (as first built, or as it stood on 1 July 1948) the extension projects beyond. The government's technical guidance on householder permitted development treats any wall that is not a front or rear wall as a side elevation, so an outrigger's side wall normally counts.
The permitted development limits for side extensions
Householder extensions are covered by Class A of Part 1, Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015. Where an extension goes beyond a wall forming a side elevation of the original house, paragraph A.1(j) says it is not permitted development if it would:
- exceed 4 metres in height;
- have more than a single storey; or
- be wider than half the width of the original house, measured at its widest point.
The general Class A limits also apply: eaves within 2 metres of a boundary must not exceed 3 metres, extensions and outbuildings together must not cover more than half the land around the original house, materials must look similar, and nothing may extend beyond the principal elevation or a side elevation fronting a highway, which matters on corner plots. Our guide to permitted development for extensions in London covers the rear depth limits in more detail.
Why most wraparounds need planning permission
The technical guidance is explicit: where an extension fills the area between a side elevation and a rear wall, the restrictions on both rear and side extensions apply. The joined extension must stay within the rear depth limits, be single storey and no more than 4 metres high, and have a total width of no more than half the width of the original house. The rear depth limits are 3 metres for an attached house or 4 metres for a detached one, or up to 6 or 8 metres through the larger home extension prior approval route outside designated land. A typical wraparound runs across the full back of the house as well as down the side, so its combined width is usually more than half the width of the house. In that case the guidance says an application for planning permission is required.
Building in stages does not get around this. Under paragraph A.1(ja), a new extension joined to an earlier one is judged on the total enlargement: the guidance's example is a permitted side extension followed by a rear extension joined to it, which needs planning permission if the combined width exceeds half the width of the house.
Conservation areas, Article 4 directions and flats
On "article 2(3) land", which includes conservation areas, paragraph A.2(b) removes permitted development for any extension beyond a side wall. In a conservation area, even a modest side infill therefore needs a householder planning application. Rights may also have been removed by an Article 4 direction or by a condition on an earlier permission, and flats and maisonettes have no householder permitted development rights at all. Check your council's conservation area and Article 4 maps before commissioning drawings, particularly in boroughs with many protected Victorian streets, such as Islington, Lambeth and Hammersmith & Fulham.
What councils look for in an application
Where permission is needed, boroughs apply their own design guidance. Hackney's Residential Extensions and Alterations SPD, which came into effect in January 2026, shows the kind of tests involved. It says extensions should be subordinate to the house, keep at least 50% of the original garden and comply with a 45-degree rule measured from neighbours' nearest habitable-room windows. On properties with an original outrigger, it says wraparound extensions will generally be acceptable outside conservation areas, subject to depth, scale and form. Inside conservation areas it will generally be possible only to infill beside the outrigger, not to wrap around it, where that is not the established character of the terrace. Other boroughs set different tests, so read your own council's guidance.
Officers will decide from 31 October
From 31 October 2026, householder applications in England must be decided by a planning officer under the national scheme of delegation. Neighbours can still object, but objections can no longer send a case to committee. Our guide to the new rules explains what that means in practice.
Fees are due to rise on 8 December
The national fee for a householder application to extend a single house has been £548 since 1 April 2026, according to the Planning Portal's fee guide. Draft fee regulations would raise this to £575 for applications made on or after 8 December 2026. The House of Lords has approved the draft, and a House of Commons committee debate is scheduled for 21 October (UK Parliament), so the figure is not yet final.
Relying on permitted development? Get a Lawful Development Certificate
If your side infill fits within the limits, you do not have to apply for anything. However, a Lawful Development Certificate for proposed works gives you the council's formal confirmation that the scheme is lawful. Buyers' solicitors often ask for one. The fee is half the full application fee: £274 for a single house at April 2026 rates. Getting it wrong now carries a longer risk. GOV.UK's enforcement guidance says unauthorised building work substantially completed on or after 25 April 2024 can face enforcement action for 10 years, rather than the previous four.
Party walls, sewers and building regulations
Side infills are often built on or close to the boundary, so read our guide to the Party Wall Act early. Thames Water says you are likely to need a build over agreement if you build within 3 metres of a public sewer or within 1 metre of a public lateral drain. Planning permission does not cover this, manholes inside the extension must be relocated, and without an agreement you may not get a building regulations completion certificate. Application charges start at £130. Building regulations approval is needed either way. See our guides to building regulations sign-off and building control charges.
A short checklist
- Check for a conservation area, an Article 4 direction or a condition removing permitted development rights.
- Compare the total width of the joined extension, including earlier extensions, with half the original house's widest point.
- Apply for a Lawful Development Certificate if the scheme is permitted development; otherwise prepare a householder application that addresses your borough's design guidance.
- Map drains and sewers, and plan party wall notices and building control before work starts.
For indicative 2026 London build-cost ranges, see our house extension cost guide. Whether you are filling a side return in Wandsworth or planning a wraparound in Ealing, you can request quotes from independent local builders when you are ready. Home Builders does not carry out building work: we ask advertisers to provide proof of insurance, and any contract is between you and the builder you choose.
Sources: MHCLG: Permitted development rights for householders, technical guidance (Class A, paragraphs A.1(e) to (ja) and A.2); Hackney Council: Residential Extensions and Alterations SPD (adopted December 2025); The Town and Country Planning (Discharge of Local Planning Authority Functions) (England) Regulations 2026, SI 2026/854; Planning Portal: Fees for planning applications in England, from 1 April 2026; Draft Town and Country Planning (Fees for Applications, Deemed Applications, Requests and Site Visits) (England) (Amendment and Transitional Provision) Regulations 2026; UK Parliament procedure browser: progress of the draft fee regulations; GOV.UK: Enforcement and post-permission matters; Thames Water: Build over agreements. This article is a summary, not legal advice; confirm the position for your property with your borough's planning service.
Frequently asked questions
Do I need planning permission for a side return extension in London?
Not always. Outside conservation areas, a single-storey side infill on a house can be permitted development if it is no more than 4 metres high, no wider than half the width of the original house and meets the other Class A limits. In a conservation area, any extension beyond a side wall needs planning permission.
Is a wraparound extension permitted development?
Usually not. The side and rear parts are assessed as one extension, and its total width must not exceed half the width of the original house. Most wraparounds run across the full rear of the house, so they need a householder planning application.
Can I build a side extension first and add a rear extension later?
The later extension is assessed together with the one it joins. If the total enlargement breaks the width or depth limits, the later work needs planning permission.
How much does a Lawful Development Certificate cost for an extension?
For proposed works the fee is half the full planning application fee, which is £274 for extending a single house at the rates in force from 1 April 2026.
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