Do I Need Planning Permission for an Extension?
Understanding planning permission rules is essential before starting any extension project. Many extensions fall under permitted development rights, meaning you may not need to apply for planning permission at all. This guide explains the rules clearly so you know where you stand before spending money on designs.
Permitted Development Rights Explained
Permitted development (PD) allows certain building works without needing formal planning permission. For house extensions, PD generally covers single storey rear extensions up to 3m from the original rear wall (semi-detached/terraced) or 4m (detached). The extension must not exceed 4m in height, must not cover more than 50% of the garden, and must use similar materials to the existing house. PD rights apply to houses only — flats, maisonettes and converted properties generally do not have PD rights for extensions.
When You Need Full Planning Permission
You will need full planning permission if your extension exceeds PD limits, if your property is in a conservation area, if you live in a listed building, if the extension faces a highway, or if PD rights have been removed by a previous planning condition (known as an Article 4 direction). Side extensions visible from a public highway also usually need planning permission. Two-storey extensions have additional restrictions — they cannot extend more than 3m from the rear wall and the upper floor must be at least 7m from the rear boundary.
Prior Approval (Larger Home Extension Scheme)
The larger home extension scheme allows single storey rear extensions up to 6m (semi-detached/terraced) or 8m (detached) through a prior approval process. This is not automatic PD — you submit a notification to your local authority, who then consult adjacent neighbours over a 42-day period. If no objections are received, or objections are considered and overruled, you can proceed. If the authority does not respond within 42 days, approval is deemed granted. The fee is currently £120.
Building Regulations vs Planning Permission
Building regulations approval is separate from planning permission and is required for almost all extensions regardless of whether planning permission is needed. Building regulations cover structural safety, fire safety, insulation, drainage, ventilation and electrical safety. You can apply through your local authority building control or an approved inspector. Fees typically range from £400 to £800. Work must not start on site until building control has been notified.
Conservation Areas and Listed Buildings
Properties in conservation areas face additional restrictions. PD rights may be reduced or removed entirely under Article 4 directions. Extensions must typically use materials that match or complement the existing building and streetscape. Listed building consent is required for any alterations to a listed building, including internal works. In Worcestershire, conservation areas are common around Worcester city centre, Malvern, Pershore and many village centres. Early engagement with the planning authority is advisable for any project involving a protected property.
The Planning Application Process
A standard householder planning application costs £258 and typically takes 8 weeks for a decision. You will need to submit architectural drawings, a site plan, a block plan, a design and access statement (for some applications), and elevation drawings. Applications are submitted online through the Planning Portal. Your neighbours will be notified and have 21 days to comment. The planning officer may negotiate changes before making a decision.
Common Scenarios and What You Need
Rear single storey extension under 3m/4m: usually PD, no application needed. Rear single storey 4-8m: prior approval required (£120, 42 days). Rear double storey under 3m: usually PD with height restrictions. Side extension: often needs planning if visible from highway. Loft conversion with dormer: usually PD but check volume limits. Wrap-around extension: usually needs planning. Extension in conservation area: usually needs planning. Any work to a listed building: always needs listed building consent.
Risks of Building Without Permission
Building without the correct permission is risky. Your local authority can serve an enforcement notice requiring you to remove or alter the work, even years after completion. When you sell the property, your buyer's solicitor will check planning history and may require retrospective applications or indemnity insurance. Mortgage lenders may also refuse to lend on properties with unauthorised works. Always confirm your position before starting on site.
Common Planning Mistakes to Avoid
The most common planning mistake is assuming your project does not need permission and starting work without checking. Retrospective planning applications are stressful, expensive and not guaranteed to succeed. Other errors include not checking whether your property has had PD rights removed by a previous condition, not consulting neighbours before submitting (leading to objections), and not engaging a professional to prepare drawings to the required standard. Starting work before building control is notified is also a common and costly error.
When to Seek Professional Advice
If you are unsure whether your project needs planning permission, get professional advice before committing to designs. A pre-application enquiry to your local authority costs around £50-£100 and gives you informal guidance. Alternatively, your architect or builder can advise based on experience. MTD Building Contractors advise on planning requirements as part of every project review and can liaise with local planning authorities on your behalf.
Frequently Asked Questions
Do I need planning permission for a single storey rear extension?
In most cases no, provided it falls within permitted development limits (3m from the rear wall for semi-detached/terraced, 4m for detached). Exceptions apply in conservation areas and for listed buildings.
Do I need planning permission for a double storey extension?
Double storey extensions have stricter PD rules. They must not extend beyond 3m from the rear wall and the upper floor must be at least 7m from the rear boundary. Many double storey extensions require full planning permission.
How long does planning permission take?
A standard householder planning application typically takes 8 weeks for a decision. The prior approval process for larger extensions takes 42 days.
How much does a planning application cost?
A standard householder planning application costs £258. Prior approval for a larger home extension costs £120. Architectural drawings for the application typically cost £1,500-£4,000.
What happens if I build without planning permission?
The local authority can issue an enforcement notice requiring you to remove or alter the work. It can also cause problems when selling the property, as buyer solicitors check planning compliance.
Is planning permission always required in a conservation area?
Not always, but PD rights are often more restricted in conservation areas. Some have Article 4 directions that remove PD rights entirely. Check with your local authority before starting work.