How much does planning permission really cost in Hillingdon?

The headline fee for a householder planning application in Hillingdon is £258. Most people see that number and think they've got a handle on the costs. They haven't. The real question isn't what the fee is — it's what else you're going to need, and that depends entirely on your property. WhatCanIBuild exists precisely because that question has a different answer for almost every address.

The fee is just the entry ticket

Pay your £258, submit online, and you'll also owe a £75.83 +VAT service charge on top. That's the floor. But costs stack up fast once you factor in what many applications actually require before they get submitted: drawings, a planning consultant, specialist reports. None of that is optional if your property triggers the wrong flags — and plenty of Hillingdon properties do.

Hillingdon has 31 conservation areas. It has significant Green Belt land. It has Heathrow Airport sitting inside its boundary, bringing its own layer of local plan policies. It has Article 4 directions that quietly remove permitted development rights in certain streets. Whether any of this applies to your specific address — and what it actually means for your project — isn't something you can read off a fee schedule.

The hidden costs most homeowners don't see coming

Most homeowners don't realise that a planning application can require supporting documents that cost more than the fee itself. Depending on your property's situation, you might need a heritage statement, an arboricultural report, a flood risk assessment, or a transport statement. Each one adds hundreds — sometimes more.

And that's before you consider what happens when an application fails. Fees aren't refunded if your application is refused or if the local authority fails to determine it within the decision window. In Hillingdon, the typical decision time is 8 weeks. If you've gone in underprepared, you're looking at resubmitting — and paying again.

What actually determines your total cost

The honest answer is: your property's specific combination of constraints, your project type, and — critically — what's been approved and refused for similar projects nearby. A rear extension on one street in Hayes might sail through. The same project two roads over might need additional reports, face objections, or have a meaningfully lower chance of approval based on local precedent.

This is where most homeowners are flying blind. Knowing you're in a conservation area is one thing. Knowing what that actually means for your proposed extension, on your street, given what Hillingdon Council has approved and refused for comparable projects in the last few years — that's a completely different level of information.

The best way to understand your real exposure before you spend anything is to run your address through WhatCanIBuild, which pulls together what's actually happened for properties like yours — not just what the rules say on paper.

If you want to know what constraints apply to your property, what similar projects nearby have cost applicants in terms of outcomes, and how your specific situation affects your chances, WhatCanIBuild gives you that picture before you commit to anything.