Conservation area check by postcode — free, against official data

Conservation-area status changes which extension rules apply to your house — it removes the larger rear-extension route, every dormer needs an application, side extensions lose their PD route entirely. Yet it's invisible from the street, and plenty of owners discover it from a validation letter after paying for drawings. Here's how to check properly, for free.

Method 1: the instant postcode check

Enter your postcode into the Siteline area report. It resolves your coordinates (via postcodes.io) and tests them point-in-polygon against the official conservation-area and Article 4 boundaries published on planning.data.gov.uk — the government's structured planning dataset. You get a yes/no for each designation with the area's name and the source cited. Coverage: our five flagship boroughs (Camden, Westminster, Islington, Hackney, Haringey), expanding.

Method 2: the council's own map

Every London borough publishes a conservation-area map or list — search '[borough] conservation areas'. This is the legally definitive source, since councils designate (and occasionally amend) the boundaries. The friction is real, though: each borough's map works differently, some are PDFs, and Article 4 directions are often published separately from the conservation areas they overlay.

Method 3: planning.data.gov.uk directly

The national platform at planning.data.gov.uk lets you search the conservation-area and article-4-direction datasets by map or address. It's the same data Siteline ingests — authoritative and improving steadily, with the caveat that some councils' submissions lag their own records. For a definitive legal answer attached to a transaction, your solicitor's local search remains the gold standard.

If the answer is yes

Read the character appraisal — the council document describing what the designation protects. It's effectively the design brief for your application.
Check for an Article 4 direction on top: it removes further PD rights street by street and is the single most-missed designation in London.
Pull your street's planning history: what's been approved three doors down is the best predictor of what you'll get.
Budget for conservation spec — matching materials are the real cost of designation, more than the application itself.

Run the free check now: postcode in, designation status out, sources cited.

Check an address

Is there an official conservation area map for all of London?

planning.data.gov.uk aggregates conservation-area boundaries nationally from council submissions — it's the closest thing to one map, and it's what Siteline queries. Individual borough maps remain the definitive legal source for their own designations.

Does being in a conservation area lower my house value?

Generally the opposite — designation correlates with the coherent streetscapes buyers pay premiums for. What it does change is the cost and flexibility of altering the house, which is priced into ambitious renovation plans rather than the home itself.

Can a conservation area boundary change?

Yes — councils review areas periodically and can extend, reduce or newly designate, usually with consultation. This is why a live data check beats a screenshot from a property listing.

My house is just outside the boundary — am I free of it?

Mostly, but applications next to a conservation area are still assessed for their effect on its setting, and your street may carry other designations (Article 4, TPOs). Check the full picture, not one layer.

How to check if you're in a conservation area — free, by postcode