The sourcing problem
Every developer is chasing the same listed sites through the same agents, which means competition and full prices. The sites that make real margin are usually found before they're openly marketed — through relationships, local knowledge, and watching the right signals. Planning data is the most structured of those signals, and almost nobody mines it systematically.
The principle is simple: a planning application is a public declaration of intent about a piece of land. Read enough of them, in the right way, and you can spot opportunities months before they reach the market.
Signal 1: approved but unbuilt permissions
A planning permission typically has to be implemented within three years or it lapses. When you find a site with consent that's approaching expiry and clearly not started on site, you've found a motivated situation: an owner who secured permission but — for funding, appetite or circumstance — never built. They may sell with the benefit of consent rather than lose it.
Filtering for older approvals with no subsequent activity surfaces exactly these. It's one of the highest-intent signals in the whole dataset.
Signal 2: refused and withdrawn applications
A refusal is a frustrated owner with a site they believe has potential. Sometimes the scheme was simply over-ambitious and a well-judged resubmission would succeed; sometimes the owner gives up and would welcome an offer. Either way, a refused application tells you two things: someone thinks this site can be developed, and the current owner has hit a wall.
Reading the refusal reasons (and any appeal outcome) tells you whether the problem is fixable design or a fundamental policy constraint — which is the difference between an opportunity and a trap. Tracking refusals across your target area is a steady source of approachable owners.
Signal 3: outline permissions and emerging patterns
Outline permissions, reserved-matters applications and a cluster of approvals in one pocket of a town all point to where development is being accepted right now. If a council has approved several backland or garden-plot schemes on a street, the policy appetite is demonstrated — and the next similar plot is a credible prospect. Planning data lets you see that pattern instead of guessing at it.
Signal 4: land assembly and neighbour activity
Larger opportunities often hide in plain sight as several small applications around a single block. Watching application activity by location — rather than one property at a time — reveals where multiple owners are active, where a ransom strip might matter, and where assembling adjoining plots could unlock something bigger than any single parcel.
Doing it systematically with the API
The manual version of all this is checking council portals one by one — unworkable across a real search area. PlanWire gives you every UK authority in one consistent feed, so you can express your buying box as a query and let the data come to you.
curl "https://api.planwire.io/v1/applications\ ?council=guildford\ &status=Refused\ &date_from=2026-03-01\ &limit=100" \ -H "X-API-Key: your_api_key"
The same approach works for approved-but-old permissions, specific application types, or a postcode radius around an area you know. Each result carries the address, coordinates, description, decision and a link to the full council record — enough to triage a long list down to the handful worth a letter or a call.
Move before the market
The advantage isn't just having the data — it's having it first. New applications are published continuously, so the developers who win are the ones who see a relevant refusal or lapsing consent within days, not when it eventually surfaces through an agent. Set up planning alerts or webhooks for your buying criteria and new matches arrive automatically — a live, self-updating pipeline of off-market situations.
Used well, planning data turns site sourcing from "wait for the agent's email" into a proactive, filtered pipeline of motivated owners — refusals, lapsing consents and assembly plays nobody else is watching.
From signal to deal
Data finds the situation; you still do the deal. Cross-reference promising sites with Land Registry for ownership, read the planning history in full to understand constraints (our guide on checking planning history covers this), and approach owners tactfully. But the hard part — finding the right sites before everyone else — is exactly what structured planning data is built to solve.