Do I Need Planning Permission for a House Extension?
In many cases, a house extension needs either planning permission or a permitted development route. The right answer depends on the property, the size and position of the extension, previous alterations and local constraints such as conservation areas, listed status or Article 4 directions.
Some smaller house extensions can be built under permitted development, but many South West London projects still need a formal planning application because the property, street, conservation area or design ambition needs closer review.
Barnes Design would normally start by checking the existing property, planning history, neighbouring approvals and the client brief. This helps establish whether a planning application, permitted development route or lawful development certificate is the most sensible next step.
Planning permission is more likely where the extension is large, close to a boundary, changes the front or side elevation, affects privacy or daylight, uses materials that do not match the existing house, or sits within a sensitive local setting.
Practical checklist
✅ Check whether the property has already been extended.
✅ Check whether the home is in a conservation area or affected by Article 4.
✅ Confirm whether the property is a house, flat or maisonette.
✅ Check extension height, depth, boundary position and materials.
✅ Review neighbouring approvals and refusals.
✅ Decide whether to use planning permission, permitted development or a lawful development certificate.
Ready to talk through your project?
Tell us a little about your property, plans or early ideas and we can help you understand the best next step.
Areas we work across in South London
Barnes Design is based in South West London and works with homeowners, developers and business owners across nearby South London areas. For house extensions, side return extensions and rear extensions, we regularly support clients in and around Wandsworth, Balham, Clapham, Tooting, Wimbledon, Battersea, Streatham, Putney, Fulham, Kingston upon Thames and the surrounding boroughs.
