How close can a neighbour's extension be to my house?
So your neighbour's planning an extension and you're wondering just how close they can get. It's one of those questions that sounds simple but gets messy fast. The rules shift depending on where you live, what kind of extension they're building, and even what type of house you've got. Privacy, light, structural stuff — all of it hangs on these distances. Let me break down the basics, the typical setbacks, and what you can actually do about it.
What is the standard minimum distance for a single-storey rear extension?
For single-storey rear extensions, the go-to rule under Permitted Development rights — at least in parts of the UK — is the 3-metre thing. But here's the thing: it's not about distance from your house. It's from the back wall of the original house to the end of the extension. For semi-detached and terraced houses, they can't build within 3.5 metres of the boundary opposite that rear wall. That boundary? Usually the fence between your gardens. Detached houses get a bit more breathing room, often 4 metres. The idea is to stop that cramped canyon feel between properties.
How close can a two-storey extension be to my house?
Two-storey stuff is way stricter. Under most planning rules, you're looking at 7 metres from the rear boundary — that's the line splitting your gardens. Why so far? It's about stopping your place from being totally overshadowed and losing light. Plus, if the eaves are within 2 metres of the boundary, they can't go higher than 3 metres. Otherwise, it'd loom over everything on your side.
What about side extensions and the boundary line?
Side extensions are where things get tight. In a lot of places, you can't even build one if it sticks out past the front of the original house. Even if it's allowed, there's usually a 0.5-metre gap from the boundary. That's for maintenance access and to stop it looking like one big wall with your neighbour's place. Sometimes, it's only okay if the boundary isn't next to a highway and the extension width is less than half the house width.
What are the "Party Wall" implications for close extensions?
If they're building on or near the boundary — think within 3 metres of your foundation — the Party Wall etc. Act 1996 kicks in (that's for England and Wales; other places have their own versions). Your neighbour has to send you a formal notice if they want to:
- Build a new wall right on the boundary line.
- Dig within 3 metres of your foundation (if it's deeper than yours).
- Dig within 6 metres of your foundation (if it's deeper by more than a metre).
Got a notice? You've got 14 days to respond. You can agree, disagree, or ask for a Party Wall Award — that's a formal agreement drawn up by a surveyor. Ignore it, and you're looking at delays and legal bills. This is your big protection against structural damage.
What if the extension blocks my light or privacy?
Right to light is a messy legal thing. Under the Prescription Act 1832, you might have a right to light if you've had it uninterrupted for 20 years. But it's not automatic for every window. If the extension cuts light to a habitable room — like a living room or bedroom — below a certain level, you could have a claim. For privacy, planning authorities often demand obscure glazing on windows within 1 metre of a boundary. If the extension gives a direct line of sight into your garden or main rooms, you can object during the planning process.
Checklist: What to do if your neighbour plans a close extension
- Check planning permission: Look up your local council's planning portal. If it's under Permitted Development, check the conditions.
- Review the Party Wall Act: Within 3 metres of your foundation? Make sure you get that formal notice. Don't just brush it off.
- Measure the distance: Grab a tape measure. Compare what they're planning to local guidelines — like 3 metres for single-storey or 7 metres for two-storey.
- Document everything: Snap photos of your property and the boundary before work starts. Keep every email or letter.
- Seek professional advice: Worried about light, privacy, or structural issues? Talk to a chartered surveyor or planning consultant.
Data Table: Typical Extension Setbacks by Type
| Extension Type | Typical Minimum Distance from Rear Boundary | Typical Minimum Distance from Side Boundary | Key Restriction |
|---|---|---|---|
| Single-storey rear (terraced/semi-detached) | 3.5 metres | N/A (rear only) | Can't go over 3 metres high if within 2 metres of boundary |
| Single-storey rear (detached) | 4 metres | N/A (rear only) | Same height rule applies |
| Two-storey rear | 7 metres | N/A (rear only) | Eaves height capped at 3 metres if within 2 metres of boundary |
| Side extension | N/A | 0.5 metres | Can't go past principal elevation; total width less than half original house |
Frequently Asked Questions
Can my neighbour build right up to the boundary fence?
Sometimes yes, but only with your okay or under specific planning conditions. If it's on the boundary, the Party Wall Act nearly always applies. Without your agreement, they usually have to set it back at least 0.5 metres — for maintenance and to avoid fights over who owns the wall.
What is the 45-degree rule for extensions?
It's a planning guideline for light impact. Draw a line at 45 degrees from the centre of your nearest main window. If it hits the neighbour's extension, that extension might be seen as overbearing and could get refused. It's not a law, just a common test planning officers use.
Can I stop my neighbour's extension if it blocks my view?
Generally, no. There's no automatic right to a view in most planning systems. A blocked view alone rarely sinks a planning application — unless the extension is so huge it damages the area's character. But if it blocks light or feels enclosing, you've got stronger arguments.
How close can a foundation excavation be to my house?
Under the Party Wall Act, your neighbour has to tell you if they dig within 3 metres of your foundation (and deeper than yours) or within 6 metres (if it's more than a metre deeper). This is to stop subsidence. No notice? You could get a court injunction to halt the work.
Resumen breve
- Distancia estándar: Una extensión de una sola planta suele requerir 3,5 metros del límite trasero para casas adosadas y 4 metros para casas independientes.
- Extensiones de dos plantas: Deben estar al menos a 7 metros del límite trasero para evitar sombras y pérdida de luz.
- Ley de Paredes Medianeras: Si la extensión está a menos de 3 metros de los cimientos de su casa, su vecino debe notificarlo formalmente.
- Derechos de luz y privacidad: Puede impugnar una extensión que bloquee la luz de ventanas principales o cree vistas directas a su propiedad.
