"Will we need planning permission?" It's the question we hear at almost every first site visit across Eastbourne and East Sussex — and the honest answer is: quite often, no. Many home extensions can be built under permitted development rights without a full planning application. But the rules have limits, the details matter, and getting it wrong can be expensive. This guide explains, in plain English, when you need permission, when you don't, and the other approvals — building regulations and the Party Wall Act — that apply either way.
The quick answer
In England, most single-storey rear and side extensions, and some two-storey rear extensions, can be built without planning permission under permitted development (PD) rights — a national set of rules that automatically grants consent for projects meeting specific size and design conditions. If your extension stays inside those limits, you can build without applying. If it goes beyond them, or your property sits in a designated area such as a conservation area, you'll need to apply through your local planning authority. The official Planning Portal extensions guide is the definitive reference, and it's the one we work to on every job.
What you can usually build without planning permission
Here are the headline permitted development limits for extensions to a house in England as they currently stand. Always confirm the latest rules before committing, as governments do amend them:
| Extension type | Key permitted development limits |
|---|---|
| Single-storey rear | Up to 4m deep (detached) or 3m deep (semi/terraced); max height 4m; max eaves 3m within 2m of a boundary |
| Larger single-storey rear | Up to 8m (detached) or 6m (semi/terraced) via the "prior approval" neighbour consultation scheme |
| Side extension | Single storey only; max width half the original house; max height 4m |
| Two-storey rear | Max 3m deep; at least 7m from the rear boundary; roof pitch matching the existing house |
On top of these, some general conditions apply across the board: the extension can't sit forward of the principal elevation (the front of the house), it can't cover more than half the land around the original house, materials should be of similar appearance to the existing property, and no part can be higher than the existing roof. "Original house" means as it stood in 1948 or as first built — so if a previous owner already extended, some of your allowance may be used up.
The 6m/8m "prior approval" route
Larger single-storey rear extensions — up to 6 metres on semis and terraces, 8 metres on detached homes — are possible under the neighbour consultation scheme. You notify the council, the council consults your adjoining neighbours, and if no valid objections are upheld within the consultation period, you receive prior approval to build. It's lighter-touch than a full application, and it's a route we've used successfully for clients who wanted a generous open-plan kitchen-diner without the full planning process.
When you definitely need planning permission
- The design exceeds PD limits — deeper, wider or taller than the figures above, or a two-storey side extension.
- Front extensions — anything projecting beyond the principal elevation facing a road.
- Flats and maisonettes — PD rights for extensions don't apply; an application is always required.
- Listed buildings — you'll need listed building consent as well as planning permission. Historic England's consents guidance explains what's involved.
- Designated land — in conservation areas (parts of Meads, Old Town and Eastbourne's seafront among them), side extensions and exterior cladding need permission, and the larger-extension scheme doesn't apply.
- Properties with PD rights removed — common on newer estates where the original consent stripped them out.
For Eastbourne homes, applications are handled by the local planning authority — you can check policies, search planning history and apply via Lewes & Eastbourne Councils' planning pages. Householder applications currently cost in the region of £260–£530 in England (fees are reviewed periodically, so check the current figure), and a decision normally takes around eight weeks from validation.
The certificate worth its weight in gold
Even when no permission is needed, we strongly recommend applying for a Lawful Development Certificate (LDC). It's formal confirmation from the council that your extension was lawful under permitted development — and when you come to sell, your buyer's solicitor will almost certainly ask for proof. An LDC costs half the standard application fee and removes any argument later. It's a small piece of admin that protects a six-figure asset.
Planning permission vs building regulations — don't confuse the two
This is the misunderstanding that catches most homeowners out. Planning permission is about whether you may build — the impact on neighbours, the street and the area. Building regulations approval is about how it's built — structural safety, fire protection, insulation, ventilation, drainage and electrics — and it applies to every extension, including ones that need no planning permission at all.
Your extension will be inspected at key stages (foundations, damp-proofing, structure, completion) and signed off with a completion certificate. The government's building regulations guidance covers the basics, and LABC publishes excellent homeowner resources. At Bear & Fox Construction we build to regs as standard, coordinate every inspection and hand you the certificate at the end — it's part of the job, not an extra.
Sharing a wall? The Party Wall Act applies
If your extension involves building on or near the boundary, excavating within 3 metres of a neighbour's foundations, or cutting into a shared wall, the Party Wall etc. Act 1996 requires you to serve formal notice on your neighbours — typically one to two months before work starts. Most neighbours simply consent, especially when they've been spoken to early and kept informed. Where they don't, a party wall surveyor draws up an award setting out how the work proceeds. It sounds daunting; in practice it's routine, and we'll flag at the survey stage whether it applies to your project.
A realistic timeline for an East Sussex extension
- Weeks 1–4: design, measured survey and drawings.
- Weeks 4–12: planning application or prior approval (skip straight ahead if you're within PD and opt for an LDC in parallel).
- Weeks 8–14: structural calculations, building regs submission, party wall notices.
- On site: roughly 8–12 weeks for a single-storey extension, 12–16+ for two-storey, weather and complexity depending.
Plan backwards from when you want the space finished. If you'd love a new kitchen-diner for next summer, the paperwork should start this autumn.
Five tips for a smooth approval
- Talk to your neighbours before anyone official does. Most objections come from surprise, not from the design itself. A friendly chat over the fence with the drawings in hand defuses nine problems out of ten.
- Match materials to the existing house. Brick, render and roof tiles that tie in with the original property keep planners and neighbours comfortable — and the finished extension looks like it was always there.
- Check the planning history of your street. If three near-identical extensions have already been approved nearby, yours has a strong precedent; if one was refused, you'll learn why before repeating the mistake.
- Get the drainage and drains search done early. Building over or near a public sewer needs a build-over agreement from the water company, and discovering that late can stall a project for weeks.
- Keep every document. Approvals, certificates, party wall awards and completion certificates all get requested when you sell — a single folder now saves a scramble later.
Frequently asked questions
Can my neighbours stop my extension?
If you're within permitted development, neighbours have no veto. Under the prior approval scheme or a full application they can object, and the council weighs the impact — which is why a considerate design and an early conversation over the fence go a long way.
What happens if I build without permission when I needed it?
The council can require a retrospective application or, in the worst case, enforcement — including alteration or removal of the work. Enforcement is rare when owners act in good faith, but it's a risk never worth taking. Check first; it costs little and protects everything.
Does a builder handle the planning application?
We work hand-in-hand with designers and structural engineers, advise on what's achievable under PD, and make sure drawings reflect what will actually be built. You get one joined-up team rather than a paper chase.
Do conservatories need planning permission?
Conservatories are treated as extensions, so the same permitted development limits apply. Most modest rear conservatories fall comfortably within them.
Talk it through before you spend a penny on drawings
The cheapest mistakes are the ones you never make. Before commissioning plans, have someone who builds extensions every week walk your plot, check your planning history and tell you honestly what's achievable — with or without an application. Bear & Fox Construction offers exactly that: a free site visit anywhere in Eastbourne and East Sussex, honest advice, and a fixed, itemised quote if you choose to go ahead. Call 01323 364462 or see our home extensions service for examples of how we work.