Around one in five planning applications in England is refused each year, and a significant portion of those refusals come down to avoidable mistakes. That figure has stayed stubbornly consistent across the last few years, which tells me something: most people aren’t losing because their project is impossible — they’re losing because they didn’t understand the rules before they started. I’ve been writing about property and planning for long enough to see the same patterns repeat. Someone buys a house, sketches out an extension, and assumes that because their neighbour did something similar, they can too. Then the refusal letter arrives, and suddenly they’re out the application fee and months of time.
The good news is that most of these problems are preventable. The rules aren’t secret — they’re just scattered across government guidance, local policies, and the Town and Country Planning Act 1990. What you need is a clear map of what requires permission, what doesn’t, and where people trip up. Here’s what you actually need to know.
What counts as development and what doesn’t
The first thing to understand is that not every change to your property counts as “development” under the Town and Country Planning Act 1990. Development means building operations, engineering works, mining operations, or a material change of use of land or buildings. If what you’re doing doesn’t fall into one of those categories, you don’t need planning permission at all. That’s the starting point, and it’s where a lot of people get confused — they either apply for permission they don’t need, or they skip it for something that absolutely requires it.
What I’d do before anything else is check whether your project falls under Permitted Development rights. These are set out in the Town and Country Planning (General Permitted Development) (England) Order 2015, and they cover a surprising amount of common home improvements. Single-storey rear extensions, for example, can go up to 3 metres deep for an attached house or 4 metres for a detached house without needing full permission — and under the Prior Approval Neighbour Consultation Scheme, those limits stretch to 6 metres and 8 metres respectively. Loft conversions get up to 40 cubic metres for terraced houses and 50 cubic metres for semi-detached and detached. Outbuildings can cover up to 50% of your garden area. But here’s the catch: these rights aren’t universal. Flats and maisonettes have no PD rights for extensions at all. Conservation areas strip many of them away. And if your property is in a National Park, Area of Outstanding Natural Beauty, or World Heritage Site, the rules tighten further.
Why getting it wrong costs more than the fee
The direct cost of a refused application is bad enough — £258 for a householder application in 2026, or £508 for minor commercial work. But the real cost is the delay. If you’re refused, you either appeal (which can take months) or redesign and resubmit (which resets the clock). Meanwhile, builders’ quotes expire, materials prices shift, and your project stalls. I’ve seen people lose a whole building season because they assumed their extension was small enough to skip permission.
There’s also a less obvious risk: enforcement action. If you build without permission where it was required, the council can issue an enforcement notice requiring you to undo the work. That can mean demolishing a new extension or restoring a property to its original use class. The enforcement process is separate from the planning application process, and it doesn’t care whether you made an honest mistake. What I’d do is spend the £50–£300 on pre-application advice from the council before submitting anything. It’s not binding, but it tells you where the objections are likely to come from, and it gives you a chance to adjust your plans before you’re locked into a formal application.
Where people go wrong — and how to avoid it
The mistakes I see most often aren’t about grand design failures. They’re about details that seem small but have big consequences. Here are the four that come up again and again.
Assuming PD rights apply without checking local restrictions
Permitted Development rights are national, but local authorities can remove them through Article 4 Directions. This is especially common in conservation areas, where even cladding your house in render or timber can require permission. If you live in a conservation area, side extensions are not permitted development at all. Outbuildings have reduced PD rights. Satellite dishes, solar panels, and flues are all more restricted. The fix is simple: check your local authority’s website for Article 4 Directions before you do anything. If you can’t find them, call the planning department and ask.
Ignoring the height and boundary rules on extensions
Even when PD rights apply, they come with strict limits. A single-storey rear extension must not exceed the height of the original house, and if it’s within 2 metres of a boundary, the eaves height can’t be more than 3 metres. Loft conversions can’t project beyond the existing roof slope on any elevation visible from a highway. Side-facing windows must be obscure-glazed. These aren’t suggestions — they’re conditions. Break them, and your PD rights don’t apply, meaning you’ve built without permission. A video doorbell won’t help you here, but a tape measure and a copy of the PD rules will.
Forgetting that Building Regulations are separate
This is the one that catches people off guard most often. Planning permission and Building Regulations approval are two completely different things. You can have full planning permission and still fail Building Regulations — and vice versa. Loft conversions, for example, always require Building Regulations approval regardless of whether they’re permitted development. The same goes for new windows, structural changes, and most electrical work. The process for Building Regulations is separate, with its own fees and inspections. Don’t assume that because you don’t need planning permission, you’re free to build without any oversight.
Overlooking the change of use rules
Converting a property from one use class to another often requires planning permission, even if no physical building work is involved. Turning a shop into a flat, for example, might be covered by PD rights in some cases, but not all. The cost for a change of use application ranges from £258 to £508 depending on the category. If you’re buying a commercial property with plans to convert it, check the use class before you exchange contracts. A real estate lawyer can help you navigate this — it’s one of those areas where professional advice pays for itself.
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| Application Type | Fee (England 2026) | Target Decision Time |
|---|---|---|
| Householder (extensions, outbuildings) | £258 | 8 weeks |
| Prior Approval (larger home extension) | £120 | 42 days |
| Full planning permission (minor commercial) | £508 | 8 weeks |
| Change of use | £258–£508 | 8 weeks |
| Listed Building Consent | Free | 8 weeks |
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How to navigate the planning system step by step
Once you understand the rules, the process itself is fairly straightforward — provided you follow the right sequence. Here’s how I’d approach it.
Check your property’s status first
Before you draw a single line, find out whether your property is in a conservation area, a National Park, an Area of Outstanding Natural Beauty, or a World Heritage Site. Check whether it’s listed. Check whether there are any Article 4 Directions in place. All of this information is publicly available on your local authority’s website or through the Planning Practice Guidance portal. If you’re unsure, a pre-application enquiry costs £50–£300 and gives you a written response from the planning officer. That piece of paper is worth its weight in gold if you later need to defend your position.
Measure everything against the PD rules
If your project is a single-storey rear extension, a loft conversion, or an outbuilding, measure it against the PD limits in the 2015 Order. For extensions: attached houses get 3 metres (6 metres with Prior Approval), detached houses get 4 metres (8 metres with Prior Approval). For lofts: 40 cubic metres for terraced, 50 cubic metres for semi-detached and detached. For outbuildings: 50% of the garden area, maximum eaves height 2.5 metres, maximum overall height 4 metres for a dual-pitch roof or 3 metres for other roofs. If you’re within these limits and your property isn’t in a restricted area, you likely don’t need planning permission. But you still need Building Regulations approval for structural work, so don’t skip that step.
Apply for Prior Approval if you’re near the limit
The Neighbour Consultation Scheme for larger home extensions is a useful middle ground. You pay £120, submit your plans, and the council has 42 days to decide. If they don’t respond, the Prior Approval is deemed granted. This is particularly useful if your extension is at the upper end of the PD limits — say, 6 metres for an attached house or 8 metres for a detached house. The council will consult your neighbours, and if there are no material objections, you’re likely to get through. If there are objections, you at least know what the issues are before you commit to a full application.
Submit a full application when required
If your project exceeds PD limits, or if you’re building something new on undeveloped land, or if you’re changing the use class of a property, you’ll need full planning permission. The application is submitted through the Planning Portal, and you’ll need a site plan, floor plans, elevations, a design and access statement, and sometimes additional reports like a flood risk assessment or a biodiversity net gain statement. The fee is £258 for a householder application or £508 for minor commercial work. The target decision time is 8 weeks, but complex applications can take longer. If you’re refused, you have the right to appeal, but the appeal process can take 6–12 months. A property lawyer can help you prepare a stronger application the first time around.
Don’t forget Listed Building Consent
If your property is listed, any work that affects its special character requires Listed Building Consent — even if it’s internal. This is separate from planning permission and is free to apply for, but the process is more rigorous. You’ll need to demonstrate that the work won’t harm the building’s historic significance. The same applies if your property is in a conservation area, though the rules are less strict. For listed buildings, I’d always recommend getting professional advice from a conservation architect or a heritage consultant before submitting anything.
Frequently asked questions
Can I build a garden office without planning permission? ▾
What happens if I build without permission and get caught? ▾
Do I need planning permission to replace windows? ▾
How long does planning permission last once granted? ▾
Can my neighbour object to my planning application? ▾
What’s the difference between planning permission and Building Regulations? ▾
Your next move
The planning system isn’t designed to trip you up — it’s designed to make sure development happens in a way that’s safe, sustainable, and respectful of the area. The problem is that the rules are scattered across multiple documents and local policies, and most people don’t know where to look. Start with your property’s status, measure your project against the PD limits, and get pre-application advice if you’re unsure. That sequence alone will save you the most common mistakes. If this was useful, you might also want to read how to choose the right UK commercial location and avoid pitfalls.
Sources and Further Reading
The empty high street: what innovative UK projects can save our towns — Explores how planning and regeneration are reshaping town centres across the UK.
Planning Practice Guidance. GOV.UK, 2024.
UK Planning Permission Guide 2026. UK Calculator, 2026.
