Planning permission checks before buying a house in London

Most London buyers pay a premium for a house precisely because of what they intend to do to it — the side return, the loft, the kitchen across the back. The planning constraints that decide whether any of that is possible are public, free to check, and almost never checked before the offer goes in. By the time the local search comes back, you have already committed to a price, a mortgage valuation and a conveyancer's fees.

What your conveyancing search will and won't tell you

This is the part buyers most often get wrong, in both directions. The local authority search (the CON29 and the LLC1 register) does reveal whether the property is in a conservation area, whether it is listed, and whether an Article 4 direction applies. That information is not hidden from you. But it arrives late — typically weeks into the transaction, after you have spent money — and it arrives as a bare designation, not as an answer to the only question you care about: can I build the thing I am buying this house to build?

• The search tells you a conservation area applies. It does not tell you that this removes your side-return extension's permitted-development route entirely.
• The search tells you an Article 4 direction exists. It does not tell you which permitted-development rights that specific direction withdraws — directions vary enormously, street by street.
• The search tells you the building is listed. It does not tell you that internal alterations you had assumed were free of planning control now need listed-building consent.
• A standard homebuyer survey (RICS Level 2 or 3) reports on condition. It does not assess planning feasibility at all.

Can you apply for planning permission on a house you don't own yet?

Yes. You do not need to own a property to apply for planning permission on it. What you must do is serve notice on the owner and complete the correct ownership certificate with the application — Certificate B, rather than the Certificate A used when you own the whole site. The council then determines the application on its planning merits exactly as it would for the owner.

In practice, buyers rarely apply before completion — an application takes at least eight weeks and the seller has no reason to wait. The realistic uses are different: a pre-application enquiry to the council, or a professional appraisal of what the constraints allow, used to decide whether to proceed and at what price. Where a scheme is fundamental to the purchase, making the offer conditional on a planning outcome is a matter for your solicitor, and sellers in a strong market will usually refuse it.

What a pre-purchase planning check should cover

• Designations at the property's own coordinates — conservation area, Article 4 direction, listed status — not a borough-level generalisation.
• What those designations do to the permitted-development route for your intended project specifically.
• The realistic planning route that follows: permitted development with a lawful development certificate, prior approval, or a full householder application.
• Indicative build costs as a range, so the scheme can be priced against the purchase.
• The honest unknowns — where the national dataset does not hold the answer, it should say so rather than guess.

The three questions worth answering before you offer

1. Is the property designated? Run the free postcode check — conservation area and Article 4 state, against the official planning.data.gov.uk geometry.
2. Does the designation kill my scheme, or just change the route? A conservation area removes side extensions and roof enlargements from permitted development, but usually leaves the basic single-storey rear allowance intact. The difference is an eight-week application, not a dead project.
3. What has actually been approved nearby? On a street of identical terraces, a consented scheme three doors down is the strongest evidence yours can cite — and a pattern of refusals is the clearest warning you will get.