What Extensions Have My Neighbours Had Approved Nearby? A 2026 Guide to Permitted Development, Costs and Added Value

Every estate agent has heard some version of this question from a vendor, a buyer, or a curious neighbour leaning over the fence: "what extensions have my neighbours had approved nearby, and could I do the same?" It sounds like a simple query about precedent. In reality, it opens up one of the most valuable conversations an agent can have with a client, because the answer isn't really about what number 12 built last summer. It's about what UK planning law and permitted development rights actually allow on that specific plot, in that specific location, right now.

Agents who can speak confidently about planning permission UK rules, not just local gossip about who got what approved, position themselves as the expert in the room. This guide sets out the planning law behind the question, so you can turn "what did my neighbours get approved" into a genuinely useful conversation about home extensions UK, permitted development UK, cost, timescale and value.

Why This Question Comes Up So Often in 2026

Extension enquiries have surged in recent years as homeowners look to add space rather than move, particularly with higher moving costs and stamp duty eating into budgets. For agents, this shows up in two ways: vendors asking whether an extension would help them sell, and buyers asking whether a property has "room to grow" before they commit to an offer.

The instinct is always to look sideways at the neighbours. If the house two doors down got a rear extension approved, surely this one can too? Sometimes yes. But planning law in the UK does not work purely on precedent between individual houses; it works on a framework of rules (permitted development rights, local planning policy and, where relevant, conservation area or listing restrictions) that apply to each property based on its own characteristics: whether it's detached, semi-detached or terraced, when it was built, and whether it sits on protected land.

That's why the smartest answer to "what extensions have my neighbours had approved nearby" is not just a list of approved schemes. It's an explanation of the rules that produced those approvals, because those same rules will determine what's achievable next door, or at the property currently on your books.

Permitted Development in the UK: What Can Actually Be Built Without Planning Permission

Permitted development rights allow many home extensions to go ahead without a full planning application, provided strict conditions are met. Understanding these conditions is the single most useful piece of planning knowledge an agent can carry into a valuation or a buyer viewing.

Standard single-storey rear extensions

Under the standard permitted development allowance, a single-storey rear extension can extend beyond the original rear wall by up to 4 metres for a detached house, or 3 metres for a semi-detached or terraced house, with a maximum height of 4 metres. This is measured from the base of the original rear wall to the outer face of the new extension wall, excluding guttering. Extensions within these limits generally don't need planning permission and don't trigger any neighbour consultation.

This is the extension type most commonly seen behind Victorian terraces and 1930s semis across the country, and it's usually the first thing worth checking when a vendor asks what's possible at the back of their house.

Larger rear extensions and the neighbour consultation scheme

Homeowners can go further, up to 8 metres beyond the original rear wall for a detached house, or 6 metres for any other house type, still capped at 4 metres in height, but only via the neighbour consultation scheme once the extension goes beyond 4 metres (detached) or 3 metres (others). This means the homeowner formally notifies the council, the council writes to adjoining neighbours, and those neighbours have the chance to object on the grounds of amenity impact. Work cannot start until the council either confirms no prior approval is needed, grants prior approval, or 42 days pass without a decision.

This is exactly why some neighbours end up with a noticeably larger rear extension than others on the same street: they've gone through the neighbour consultation route rather than staying within the automatic limits. Crucially, this larger allowance does not apply on article 2(3) land, which covers conservation areas, National Parks, Areas of Outstanding Natural Beauty, the Broads and World Heritage Sites. If the property is in a conservation area, this bigger rear extension option simply isn't available under permitted development, regardless of what a similar-looking house has managed a few roads over in an unprotected area.

Wraparound extensions (side plus rear combined)

Where an extension fills the corner between a side wall and the rear wall, both the rear extension limits and additional restrictions apply together. The rear projection must stay within 6 metres (8 metres if detached), or reduced further on article 2(3) land, the whole structure must be single storey, height capped at 4 metres, and the total width of the extension cannot exceed half the width of the original house. Go beyond any of these and it drops out of permitted development entirely, meaning a planning application becomes necessary.

Adding storeys upward

Since 2020, permitted development rights have included the option to add storeys on top of an existing house rather than extending outward. Houses with two or more storeys can potentially add up to two additional storeys; single-storey houses can add one. This only applies to houses built between 1 July 1948 and 28 October 2018, and the new storeys must sit on the principal part of the house. The extended building cannot exceed 18 metres in total height, each new storey is limited to adding no more than 3.5 metres, and where the house isn't detached, the new roof line cannot exceed the neighbouring roof height by more than 3.5 metres.

Unlike the rear extension allowances above, this route always requires prior approval from the local planning authority, covering matters like external appearance, impact on neighbouring amenity and loss of light. It is never automatic, and it doesn't apply in conservation areas, National Parks, AONBs or to listed buildings.

What you almost never get for free: front extensions

One of the most common misunderstandings agents encounter is homeowners assuming that if the house next door has a bigger frontage or a converted porch, they can do the same. Permitted development does not allow extensions forward of the wall that forms the principal elevation of the house, and on corner plots, side walls that front a highway carry additional restrictions too. "Beyond the wall" includes the space in front of an imaginary line drawn from the end of that wall out to the property boundary. In practice, this means front extensions almost always need a full planning application, whatever the neighbours have built.

Conservation areas change everything

If a property sits on article 2(3) land, several permitted development rights are switched off entirely. Cladding the exterior in stone, artificial stone, pebble dash, render, timber, plastic or tiles is not permitted development. Extensions beyond any side wall are not permitted. A rear extension of more than a single storey is not permitted.