Step-by-Step Guide to Planning Permission for a Home Extension in the UK

Everything you need to know before you apply.

Why Planning Permission Matters

Planning permission is the formal approval from your local council to carry out building work.

If your extension needs it and you build without it, you risk:

  • Being ordered to undo the work

  • Fines or legal issues

  • Difficulty selling your home later

The good news? Not every extension needs permission — some can be built under Permitted Development Rights. This guide will help you work out which applies to you, and how to get planning permission if you need it.

Step 1 – Check if You Actually Need Planning Permission

Some extensions fall under Permitted Development — meaning you can build without full planning permission if certain conditions are met, such as:

  • It’s within size limits (e.g., rear extensions no more than 3m deep for terraced/semi-detached, 4m for detached — unless using Larger Home Extension scheme).

  • It’s not higher than the highest part of the existing roof.

  • Materials are similar in appearance to the existing house.

Exceptions:

  • Listed buildings (need Listed Building Consent regardless)

  • Homes in conservation areas, national parks, Areas of Outstanding Natural Beauty

  • Flats and maisonettes (no Permitted Development rights)

Tip: Your architect can do a Permitted Development check before you commit to design work.

Step 2 – Prepare Your Design

Even if you don’t need planning permission, you’ll still need clear plans for building control and your builder.

If you do need permission, your design will be assessed against local planning policy, which considers:

  • Impact on neighbours (privacy, overshadowing)

  • Size and scale

  • Appearance and materials

  • Effect on street scene or heritage setting

Step 3 – Gather the Right Documents

A typical planning application includes:

  • Location plan & site plan (OS map)

  • Existing and proposed floor plans

  • Existing and proposed elevations

  • Roof plans (if applicable)

  • Design & Access Statement (required for some projects)

  • Application forms and fee

Step 4 – Submit Your Application

Applications are made online via the Planning Portal (planningportal.co.uk) or directly to your local council.

  • Householder application fee (England): £578

  • Larger schemes or non-householder projects have different fees.

Step 5 – The Council’s Validation Process

The council will check your application is complete before starting the official clock.

If anything is missing, they’ll ask for it before progressing.

Step 6 – Public Consultation & Officer Review

  • Neighbours are notified and have 21 days to comment.

  • A planning officer will visit or review the site remotely.

  • They’ll assess the application against the local plan and any objections received.

Step 7 – Decision

Decisions are usually made within 8 weeks for householder applications. The result will be:

  • Approved – you can proceed (subject to any conditions)

  • Approved with conditions – you must meet certain requirements

  • Refused – you can amend and reapply or appeal

Step 8 – Discharge Conditions (if applicable)

Some approvals come with conditions, e.g., submitting material samples for approval before construction.

Failing to discharge these can make your approval invalid.

Step 9 – Keep Your Approval Safe

Planning permission usually lasts 3 years from the date of approval. You must start work within this time or reapply.

Typical Planning Permission Timeline

Stage Timeframe

Pre-application advice (optional) 4 weeks

Application preparation 4 weeks

Validation & consultation 8 weeks

Discharging conditions 6 weeks

Common Reasons for Refusal

  • Overlooking or overshadowing neighbours

  • Design out of keeping with surroundings

  • Excessive size/scale

  • Loss of light or amenity space

  • Impact on heritage or protected trees

Planning Permission Costs Beyond the Fee

  • Architect’s planning drawings: Often part of the design package (10–15% of build cost for full service).

  • Planning consultant (if complex): £1,000–£3,000.

  • Heritage consultant (if in a conservation area/listed): £800–£2,500.

Homeowner Checklist Before Applying

  1. Confirm if you need permission or can use Permitted Development.

  2. Have a clear design that meets policy.

  3. Prepare accurate, scaled drawings.

  4. Budget for application fee + supporting consultants.

  5. Allow enough time for approval before you want to start building.

Need help navigating planning?

I offer a £150 on-site consultation where we review your ideas, check local policies, and advise on the best route to approval.

To Book Your Consultation: Email at studio@natureworksdesign.co.uk or call me on 0203 304 2338.