Kitchen and house extensions in London. Rear, side return and wraparound extensions, designed, priced and built by one team.
The most expensive assumption in a London renovation is a date. A homeowner is told the council will decide in eight weeks. They book the builder for week nine. Then they find that the eight weeks were only the middle of the process. This post is about what actually sits either side of that decision. It also covers what to do when the answer is no.
It is written from the questions clients put to NU every week. It also reflects how we take a scheme from first call to consent.
Do you need planning permission at all?
It depends on the property, the proposed work and the existing restrictions. Some work may be permitted development. Check eligibility for the actual building before relying on that route. Householder permitted development rights apply differently to flats and maisonettes than to houses. Prior alterations and restrictions matter.
An Article 4 direction can remove specified permitted development rights within its defined scope. Check the actual direction and the actual property. Do not assume every restriction is the same. You may want certainty that work is lawful. A lawful development certificate is the formal route. It is different from building regulations approval and should reflect the exact proposal.
A decision date is not a start date
Allow for surveys, design and validation before the authority’s assessment period even begins. Requests for information, consultation and revisions can extend the overall timeline. Never treat an indicative decision date as a guaranteed site start.
And consent is not the finish line either. Read the decision notice for conditions. Check the other approvals and agreements the works need. Building control, structural calculations and the party wall process all sit alongside planning. So does Thames Water agreement, where a public sewer is close. Design, technical and contractual readiness remain separate questions from the permission itself.
Everything starts with design. You might go straight to build costs or programme before the scope exists. Then the contractor cannot price the project properly. Every number stays provisional. Design first, then scope, then cost certainty.
Pre-application advice, and what it is not
Pre-application advice can be useful where policy, heritage, scale or neighbour effects are uncertain. Its value depends on the question asked and the information supplied. It is not planning permission. No responsible project team can guarantee a council’s decision. Good preparation identifies the policy issues and improves what is submitted. The decision stays with the authority.
If planning is refused
Refusal is not the end of the project. Review the reasons with the designer or planning consultant before choosing a route. There are three: a revision, a new application, or an appeal. The strongest route depends on the specific refusal and the practical brief. It does not depend on which one feels quickest.
Neighbour objections are not an automatic refusal. The authority assesses the application against the relevant planning considerations. A proposal should address neighbour effects properly. Do not assume that either support or an objection decides it.
You may later want to change the approved design. Check changes against the approved documents and conditions before implementation. Get the route for the amendment confirmed rather than building it and hoping. The costs of the extension are set out in rear extension cost in London. See also loft conversion costs in London.
How NU handles it
NU is a design and build contractor in Fulham. Architecture, interior design, project management and construction sit under one contract. Planning permissions are handled in house. Structural engineers and party wall surveyors are coordinated as part of the job. We work through a twelve step process from the first call to handover. The planning stage is one step in a sequence. It is not a hurdle you clear alone.
Thinking about this on your own house? Fill out the contact form or call 020 7731 6841. Let’s get you booked in for a free call with Nick.
This is the work we do. Kitchen and house extensions in London, or ask for a cost estimate.
Published 14 September 2026. Written by the NU Projects studio, edited since for house style and accuracy.