A town of side gardens
Over a third of households across BCP live in a detached house, against roughly one in ten in a terrace. In a terraced town people fight over a metre and a half beside the kitchen. On a detached plot the question is which way to grow.
Outside a conservation area the national rules are kind to a detached house. A single-storey rear addition can go 4 metres deep without an application (3 metres on a semi or terrace), up to 4 metres high. Prior approval, with neighbours notified first, stretches that to 8 metres detached or 6 otherwise. A single-storey side addition is allowed too, up to 4 metres high and no wider than half the original house. Going up two storeys at the back is possible within 3 metres of depth, provided the new work stays at least 7 metres from the rear boundary.
Two exceptions catch a lot of Bournemouth owners. Flats have no householder permitted development at all, and flats make up more than a third of BCP's homes. The other is conservation areas, of which Bournemouth has 20. Inside one, any side addition needs planning permission, so does anything over one storey at the back, and so does cladding. Render and timber boarding both count. The Meyrick Park and Talbot Woods appraisal spells this out for its villa roads.
The council still lists its 2008 householder guide, Residential Extensions, for the Bournemouth area. Read it before paying for drawings.
Sand, clay, cliffs and the Stour
The ground under the town is a mix. The British Geological Survey maps Palaeogene beds, where clays of the Poole Formation alternate with sands, and Branksome and Boscombe sands nearer the sea. About half the district is covered by river terrace sand and gravel. The survey also flags old landfill and former clay workings. One garden can sit on gravel and the next on soft clay, so dig trial holes before the footings are designed.
On the cliff top, ask harder questions. The East Cliff slipped in 2016 and had further minor slips in 2024 and 2025, with rainfall and groundwater named as the forces at work. Near the edge, pay for a ground investigation.
Then the trees. Talbot Woods began as pine plantation in about 1812. In a conservation area any tree with a stem over 7.5cm across, measured 1.5 metres up, needs six weeks' written notice before work. BCP maps trees under preservation orders, and cutting one without consent is a criminal offence.
The council says Bournemouth carries less tidal and river flood risk than Christchurch or Poole. The Stour, on the northern edge, is the exception. Environment Agency warning areas cover Throop, Throop Road and Iford Bridge Home Park. In Flood Zone 2 or 3 an application needs a flood risk assessment, and the Agency's standing advice asks for a floor 600mm above the estimated flood level (300mm where the level is well known), or flood-resistant construction.
How each type suits Bournemouth
Ordered for a town of detached houses and big gardens.
Single-storey rear. The easy win on a detached house outside a conservation area, where 4 metres needs no application and prior approval can take it further. In Talbot Woods it is still allowed within those limits, without cladding.
Kitchen. On a north-facing plot, rooflights will do more for the room than another metre of floor.
Wrap-around. Suits a detached house or semi with a side drive. It counts as a side addition, so inside a conservation area it's always a planning application.
Two-storey. The usual way to add a bedroom on a big plot. Expect officers to look at the gap left to the boundary and the neighbours' windows, and in a conservation area it's never permitted development.
Open plan. Knocking the old back rooms of a brick villa into one needs a calculated beam. On clay or loose sand the padstones and the footings under them matter as much as the steel.
Ground-floor bedroom. With 21.7% of BCP's population aged 65 or over, this brief comes up often. Keep it part of the house. A self-contained annex near heathland runs into separate rules (see below).
Home office. With a long garden the temptation is a cabin at the far end. Attached, it shares the heating and the broadband, and the footings stay clear of the trees at the end of the garden.
Side return. Rarer here, since true terraces are scarce. Filling the narrow passage beside one in Winton counts as a side addition in planning terms.
Planning. First check three things on the council's maps: conservation area, protected trees and flood warning area. If you own a flat, assume an application.
Cost. No local figure from us. Footings on gravel and footings among pine roots on clay are priced very differently. Three site visits will show you how.
Annexes and the heath
Bournemouth sits among protected Dorset heathland, and the framework the council uses has a clear line on householders. An extension that stays part of the house is fine, even within 400 metres of heath. So is a granny annex that shares the house. Once it works as a separate home, with its own kitchen and front door, it's treated as a new dwelling. Within 400 metres that isn't allowed. Between 400 metres and 5 kilometres it's charged towards heathland mitigation as if it were a flat.
The council's heathland map shows where you stand. Look before you design the annex, because a shared kitchen can be the difference between approval and refusal.
Where these facts come from
- GOV.UK: permitted development rights for householders, technical guidance
- BCP Council: Bournemouth local plan and householder guidance
- BCP Council: conservation areas
- BCP Council: trees in conservation areas
- BCP Council: tree preservation orders
- BCP Council: strategic flood risk assessment, Bournemouth area
- Environment Agency: Lower Stour from Longham to Christchurch flood warning area
- GOV.UK: flood risk assessment standing advice
- Dorset Heathlands Planning Framework 2020 to 2025 SPD
- BGS: geology of the country around Bournemouth
- BCP seafront projects: East Cliff
- Dorset Council: BCP area profile (Census 2021)
How FirQuote works in Bournemouth: We connect you with local specialists who visit your property before giving you a price. You get up to 3 written quotes — no call centres, no estimates from photos, no obligation to accept any quote.
Questions people in Bournemouth ask
We're near the Stour at Throop. Will an extension need a flood risk assessment?
If the house is in Flood Zone 2 or 3, yes. Throop and Throop Road fall in Environment Agency warning areas. The standing advice for small extensions sets out what the assessment covers, including the finished floor level.
There's a big pine near where we want to build. What do we check?
Look it up on BCP's protected trees map. If there's no order but you're in a conservation area, any tree with a stem over 7.5cm across needs six weeks' notice before work. Get an arboricultural report so the foundations are designed around the roots.
Can my mother's annex have its own kitchen if we live near heathland?
Within 400 metres of protected heath, a self-contained annex counts as a new home and isn't allowed. Further out it can be, with a heathland mitigation payment. An annex that shares your kitchen and entrance is treated as an extension.
We live in Talbot Woods. Can we use the 8 metre prior approval route?
No. That route doesn't apply in conservation areas. Without an application you're limited to 4 metres for a detached house, single storey, with materials of a similar appearance and no cladding.