Neighbor Report: A Homeowner's Guide to Checking What's Really Allowed Next Door

If you have searched for "neighbor report" while trying to work out what a neighbour is building, or whether you need to flag something to your council, you are not alone. It is not an official UK planning term, and you will not find it defined in any planning legislation or council guidance. What most people actually mean is something more practical: how do I find out whether that extension, loft conversion or new outbuilding next door is lawful, and what can I do about it if I think it is not?

This guide takes that angle. Rather than repeating the standard explanation of how councils formally notify neighbours about a planning application (a separate topic covered elsewhere), it walks you through how to build your own picture of a development: checking the rules that let building work go ahead without planning permission at all, spotting the red flags that suggest permission should have been sought, and knowing what to do next. This is useful whether you are worried about a build next door, or you are the one extending and want to be confident you will not end up on the receiving end of a complaint.

Why "Permitted Development" Is the Real Starting Point

Most disputes between neighbours in England start from a false assumption: that any significant building work must have gone through the council and been advertised for objections. In reality, a huge proportion of extensions, loft conversions, porches and outbuildings are built under permitted development (PD) rights, meaning no planning application, no notification letters, and no public consultation ever happens. If you want to compile any kind of informal "neighbour report" on a property, understanding these PD limits is essential, because they tell you what your neighbour is allowed to do without asking anyone.

Below are the limits that most commonly matter in real disputes.

The 50% Curtilage Coverage Limit

Under the permitted development rules for house extensions, there is a hard ceiling on how much of a garden can be built over. Once you add up all buildings within the curtilage, other than the original house itself, they cannot cover more than 50% of that curtilage. This is a cumulative test: it counts the existing house extensions, any new extension being proposed, sheds, garages, greenhouses and outbuildings, even ones that have stood since before 1948. The only thing excluded from the calculation is the footprint of the original house.

This is one of the most commonly missed rules by homeowners doing DIY extensions, and it is a useful first check if you are assessing a neighbour's project. A modest single-storey rear extension might look harmless in isolation, but if the garden already has a large shed, an old garage and a previous extension, it could easily tip the plot over the 50% threshold, meaning the new work is not permitted development at all and needs a full planning application.

Nothing in Front of the House Without Permission

Permitted development rights are deliberately tight at the front of a house. An extension is not allowed to go beyond a wall that forms the principal elevation (generally the main frontage facing the street), or beyond a side wall that itself fronts a highway. This "beyond the wall" restriction is measured using an imaginary line drawn from the end of that wall to the property boundary, not just the literal wall itself.

This matters particularly on corner plots, where a side wall facing a side road counts as fronting a highway, triggering the same restriction. In practice, this means front extensions and porches that project past the building line almost always require a planning application, regardless of size. If you see a substantial new structure appearing at the front of a neighbouring property, that is one of the first things worth checking.

Side and Rear Extensions: What PD Actually Allows

For a single-storey rear extension on a house that is not in a conservation area, National Park, AONB, World Heritage Site or on a site of special scientific interest, permitted development allows:

• Up to 8 metres beyond the original rear wall for a detached house
• Up to 6 metres beyond the original rear wall for any other type of house (semi-detached or terraced)
• A maximum height of 4 metres in either case

Anything beyond 4 metres for a detached house, or 3 metres for any other house type, up to those larger maximums, does not fall outside PD entirely, but it does trigger a specific process called the neighbour consultation scheme (more on that below). Crucially, none of these larger allowances apply if the property sits on article 2(3) land, which covers conservation areas, National Parks, AONBs, the Broads and World Heritage Sites. In those locations, the normal, smaller PD limits apply instead, and the extended allowances simply do not exist.

Conservation Areas: The Extra Restrictions

If the property you are looking into sits in a conservation area, National Park, AONB, the Broads, or a World Heritage Site, three extra restrictions kick in automatically under permitted development rules:

1. No side extensions. Any extension beyond a side wall is not permitted development in these areas, full stop.
2. No two-storey rear extensions. A rear extension is limited to a single storey; anything with more than one storey needs planning permission.
3. No new cladding or render. Re-facing the exterior with stone, artificial stone, pebble-dash, render, timber, plastic or tiles is not permitted development in these locations.

This is a common source of genuine breaches. Homeowners in conservation areas sometimes assume the same generous rear extension allowances apply everywhere in England, and start work on a two-storey rear addition or re-render the whole house, without realising the conservation area status has switched off those rights.

Loft Conversions and Roof Extensions

Loft conversions have their own permitted development class, and it comes with two points that regularly catch people out. First, roof balconies are never included: a loft conversion that creates a balcony is not permitted development, regardless of size, and needs a full planning application. Second, and more significant for anyone in a designated area, roof extensions of any kind (dormers, roof enlargements, and so on) are not permitted development at all on article 2(3) land. That means if the house is in a conservation area, National Park, AONB or World Heritage Site, any dormer loft conversion needs planning permission, with no PD fallback whatsoever.

Porches

Porches are a small but frequent flashpoint, usually because they sit right at the boundary with the street. A porch is permitted development only if all three of the following are true: it covers no more than 3 square metres of ground externally, no part of it is higher than 3 metres above ground level, and no part of it sits within 2 metres of any boundary that fronts a highway. Fail any one of those tests and the porch needs planning permission, however modest it looks.

The Neighbour Consultation Scheme, in Brief

Because larger single-storey rear extensions (over 4 metres for detached houses, over 3 metres for others) are not "full" permitted development, they come with a built-in check called the neighbour consultation scheme. The homeowner notifies the council of their intention to build, the council in turn writes to the adjoining neighbours, and those neighbours have a set period to raise objections. Work cannot legally start until one of three things happens: the council confirms no prior approval is needed, the council grants prior approval, or 42 days pass with no decision issued at all.

If you are the one building and using this route, keep dated copies of everything you submit to the council, because the 42-day clock matters if the council goes quiet. If you are a neighbour who has received one of these notifications, note the deadline for objections carefully; missing it means the build can proceed even if you have concerns about loss of light or overlooking.

How to Compile Your Own Neighbour Report, Step by Step

If you are trying to work out whether something being built near you is lawful, here is a practical sequence to follow.

1. Check the Council's Planning Portal First

Every local planning authority maintains a public online register of planning applications, usually searchable by address or postcode. Search the property in question. If there is an approved application matching the work you can see, that is your answer; the build is authorised, and any objection window has likely already passed. If there is nothing on the register, that does not automatically mean something is wrong, since a lot of work is legitimately done under permitted development with no application at all.

2. Establish Whether the Property Is on Article 2(3) Land

This single check changes almost everything. Your council's website will confirm whether the address sits within a conservation area, and mapping tools on the planning portal typically show National Park, AONB and World Heritage Site boundaries too. If the property is on article 2(3) land, apply the tighter rules: no side extensions, no two-storey rear extensions, no re-cladding, no roof dormers, and none of the larger 6m/8m rear extension allowances.

3. Measure What You Can See Against the PD Limits

From a public vantage point (do not trespass to get a better look), you can often judge roughly how far a rear extension projects, whether it is single or double storey, and whether it looks close to or beyond the property's side boundary. Compare this against the limits above. A two-storey rear extension in a conservation area, or a side extension anywhere in one, is one of the clearer signs that planning permission should have been sought.

4. Check the Curtilage Coverage If You Suspect Over-Development

This is harder to assess from the street, but aerial imagery available through most council mapping portals can give a rough sense of how much of a garden is already covered by outbuildings, garages and previous extensions. If a plot already looks heavily built-up and a further extension is underway, the 50% curtilage limit may well be in play.

5. If You Suspect a Genuine Breach, Contact Planning Enforcement

If your research points to work that appears to exceed permitted development limits and has not gone through a planning application, the correct next step is not a neighbour dispute letter, but a report to your council's planning enforcement team.