What Extensions Have My Neighbours Had Approved Nearby? A 2026 Guide for Estate Agents

Almost every valuation appointment in 2026 throws up some version of the same question. A vendor wants to know if their side return could become a kitchen-diner. A buyer standing in a pokey Victorian terrace asks whether the house next door's rear extension means they could do the same. And increasingly, homeowners simply type "what extensions have my neighbours had approved nearby" into Google before they've even picked up the phone to an architect.

For estate agents and branch managers, this is more than idle curiosity. Planning history on a street is genuinely useful market intelligence. It tells you what's realistic, what's likely to be resisted by a council, and what buyers should budget for once they move in. Agents who can answer this question with confidence, rather than a shrug and "you'd need to check with the council", stand out at valuation stage and win more instructions.

This guide explains how to research neighbouring extensions properly, what that research can and can't tell you, and how the underlying permitted development rules explain the patterns you'll see on any street in England.

Why Neighbouring Extensions Matter So Much Right Now

Home extensions UK-wide remain one of the most popular ways to add space without the cost and disruption of moving. Stamp duty, high mortgage rates and a shortage of family-sized stock in many areas mean more homeowners are choosing to extend rather than relocate. That means more planning applications, more permitted development notifications, and more visible evidence on every street of what's achievable.

For vendors, a neighbour's successful rear extension or loft conversion is often the first thing that gets mentioned at a valuation. For buyers, it's reassurance that the street has "form" for extending, and that a similar project on their new home is unlikely to face objection. For agents, it's a genuine differentiator: bring hard planning evidence to a valuation and you look like the expert who's done their homework, not just the agent with the shiniest brochure.

How to Actually Research What's Been Approved Nearby

Start with the council's planning register

Every UK local planning authority holds a public register of planning applications, searchable by address, postcode or map area. Most portals let you draw a radius around a property, typically 250 to 500 metres, and pull up every application submitted in recent years. This is the single best source for answering "what extensions have my neighbours had approved nearby" with actual evidence rather than guesswork.

When searching, look for:

• Full planning permission applications for extensions, which will include decision notices and often the approved drawings.
• Prior approval applications, which cover the larger permitted development routes such as bigger single-storey rear extensions and upward extensions adding extra storeys.
• Lawful Development Certificate applications, where a homeowner has asked the council to formally confirm that works either did or would comply with permitted development rights.
• Refusals and appeals, which are just as informative as approvals; a pattern of refusals for two-storey side extensions on a street tells you something important.

Cross-reference with aerial imagery and Street View history

Planning registers only show what's been through the council. A huge number of extensions never appear there at all, because they were built entirely under permitted development with no need for prior approval or a certificate. Comparing historic aerial photography and Street View imagery over several years against the planning register helps you spot extensions that were simply built, not applied for, so you get a fuller picture of the street's real extension activity rather than just its paper trail.

Note the application type, not just the outcome

An approval for a single-storey rear extension tells you very little on its own unless you know how large it was relative to the house. A detached house extending 4 metres beyond its original rear wall is doing something entirely different from a semi-detached house doing the same, because the standard permitted development limit for a non-detached house is 3 metres, not 4. If a semi got permission for a 4 metre extension, it likely needed full planning permission rather than relying on permitted development, which is a useful clue about how the council viewed the impact on neighbours.

What Neighbour Precedent Tells You (and What It Doesn't)

This is the point most homeowners, and quite a few agents, get wrong. Seeing that the house three doors down built a large rear extension does not automatically mean your vendor's house can do the same.

Permitted development rights are based on the original house, meaning the house as it was first built or as it stood on 1 July 1948, not as it exists today after previous extensions. Two houses that look identical from the street can have very different remaining permitted development allowances if one has already been extended and the other hasn't.

Precedent is also not a legal entitlement. Planning officers assess each application on its own merits. A council granting planning permission for a two-storey side extension on one plot doesn't bind them to approve an equivalent scheme two doors along, particularly if there are differences in plot size, boundary relationships, or impact on daylight to neighbouring windows.

What neighbour research does reliably tell you:

• Whether the street sits within a conservation area or other designated land, which materially changes what's possible.
• The kind of scale councils in that area tend to support, useful when briefing a vendor on realistic expectations.
• Whether there's a track record of the council resisting particular extension types (two-storey rear extensions and dormer-heavy loft conversions are common flashpoints in some boroughs).
• Whether extensions in the area were built under permitted development or needed full planning permission, which affects how quickly a similar project could proceed.

The Rules Behind the Pattern You'll See on Any Street

Understanding the permitted development framework helps you read a street's planning history properly, rather than just listing approvals without context.

Standard single-storey rear extensions

The baseline permitted development allowance for a single-storey rear extension lets a detached house extend up to 4 metres beyond the original rear wall, and any other house (semi-detached or terraced) up to 3 metres, with a maximum height of 4 metres. Extensions within these limits generally don't need planning permission and won't always appear on the planning register at all, which is why aerial comparison matters.

Larger rear extensions and the neighbour consultation scheme

Go beyond those standard limits and a different route kicks in. A detached house can extend up to 8 metres beyond the original rear wall, and other houses up to 6 metres, still capped at 4 metres in height, but only via the neighbour consultation scheme. The homeowner notifies the council, the council notifies adjoining neighbours, and those neighbours have the chance to object. Work can't start until the council either confirms no prior approval is needed, grants prior approval, or 42 days pass without a decision. This route is a common source of "approved" entries on the register that aren't full planning applications, and it's a strong sign that a street can support genuinely large single-storey extensions, provided the property isn't in a conservation area.

Why you rarely see approved front extensions

Extending forward of the wall that forms the front of the house, or forward of a side wall that fronts a road, isn't permitted development. This includes the space in front of an imaginary line drawn from the end of that wall to the property boundary, and corner plots face an additional restriction on the side facing the highway. That's why front extensions are rare on any street and almost always require a full planning application, so if you spot one on the register, it's worth reading the decision notice closely.

Adding storeys on top

Since 2020, homeowners have had a permitted development route to add extra storeys on top of a house: up to two additional storeys where the house already has two or more, or one additional storey on a single-storey house. This only applies to houses originally built between 1 July 1948 and 28 October 2018, and always requires prior approval from the council, never automatic sign-off. There are firm caps too: the finished house can't exceed 18 metres in total height, each new storey can add no more than 3.5 metres, and on non-detached houses the new roofline can't rise more than 3.5 metres above the neighbouring property. It doesn't apply to listed buildings or anywhere on article 2(3) land (conservation areas, National Parks, AONBs, the Bro