How much does planning permission really cost in Hillingdon?

Most Hillingdon homeowners start by googling the application fee. They find £548, nod, and assume that's the answer. It isn't — and the gap between what you expect to pay and what you actually end up spending is where most projects run into trouble. Until you see what applies to your exact address — free, in about a minute, you're working with an incomplete picture.

The £548 fee is the floor, not the ceiling

The government-set householder fee is fixed at £548 for most standard applications. But that figure doesn't include pre-application advice, architect fees, specialist surveys, or — in some cases — the cost of resubmitting after a refusal. Most homeowners don't realise that a refusal doesn't come with a refund. If Hillingdon Council doesn't approve your application, you lose the fee and have to start again.

There's also the Planning Portal service charge on top of the application fee for online submissions. It's not huge, but it's another cost most people don't factor in before they start.

Hillingdon's constraints are unusually varied — and unusually consequential

This is where things get complicated fast. Hillingdon isn't a uniform borough. The western fringes — Harefield, the Colne Valley, around Ruislip Woods — sit in Green Belt. That changes what's possible, what needs permission, and what the council is likely to approve. But Green Belt isn't the only constraint that matters.

Conservation areas cover Harefield Village, Ruislip Village, Ickenham Village, and parts of Uxbridge. If your property sits within one — or even close to one — the rules around extensions, outbuildings, and anything visible from the street shift significantly. Listed buildings cluster around St Mary's Harefield and the historic village cores, and their influence can extend to neighbouring properties too.

Then there's the south of the borough. Heathrow's noise contours don't just affect quality of life — they can affect what planning conditions get attached to approved projects, particularly anything involving habitable rooms or roof alterations. And flood zones along the Colne and Frays rivers add another layer of assessment for properties in those corridors.

The best way to understand how your specific combination of constraints affects your chances is to check what your property's constraint mix actually means for your project.

What your neighbours' applications tell you

The most useful information isn't in the rulebook — it's in the local decision record. What has Hillingdon Council actually approved or refused for projects like yours, on streets like yours? A similar extension two roads away might have sailed through. The same design on your street might have been refused twice. That pattern matters enormously for whether your project is likely to cost £548 or considerably more.

Pre-application advice, specialist acoustic reports near Heathrow, flood risk assessments, heritage statements in conservation areas — these aren't always required, but when they are, they can each add hundreds or thousands of pounds before you've submitted anything.

The best way to know what you're actually facing — including the approval record for your specific street — is to see what's been approved near you and what that means for your odds, free, no signup needed.