Planning permission checker
Our free planning permission checker tells you whether your home improvement project needs planning permission — in 2 minutes, using real council data and the live constraints on your specific property. No signup, no email required, no hidden fees.
Try the checker now
Enter your postcode and tell us what you’re planning. We’ll pull your live property constraints, apply the GPDO 2015 rules, and give you an instant verdict.
Check my property — freeWhat a planning permission checker actually does
A planning permission checker takes two inputs — your property and your project — and tells you whether you need to apply for planning permission before building. The work behind the scenes is harder than it sounds, because the answer depends on three different things that all have to be checked against each other.
1. What kind of property you have
Most permitted development rights under the GPDO apply only to houses— detached, semi-detached, terraced, and end-of-terrace. Flats and maisonettes don’t have Class A rights, so any external alteration needs planning permission. Listed buildings have an additional consent layer on top of planning permission.
2. Your exact project
Each type of project has its own class in the GPDO: Class A for house extensions, Class B for loft conversions, Class C for roof alterations, Class D for porches, Class E for outbuildings, Class F for hard standing, and so on. Each class has specific dimension, height, material, and location limits. A checker applies those limits to the project you describe.
3. Live constraints at your address
Even a project that would normally be permitted development can lose those rights because of your property. Conservation areas strip Class A side extensions and cladding. Article 4 Directions remove specific PD rights on individual streets. Designated land (AONBs, National Parks, World Heritage Sites) cuts dimension limits in half. Tree Preservation Orders, flood zones, and green belt all add their own restrictions. A good checker queries all of these in real time using your postcode.
What makes our planning permission checker different
Most online planning permission “checkers” are simplified flowcharts that ignore the constraints specific to your address. They ask a few yes/no questions and produce a generic answer. Ours is different in three ways.
- ✓Live constraint data. We query planning.data.gov.uk and the Environment Agency in real time for your exact postcode. Conservation area polygons, Article 4 boundaries, listed building records, TPO zones, flood zones, and more — all checked against your specific property, not a generic postcode area.
- ✓Real council decisions. For every project type in every council we support, we maintain a database of recent planning decisions. That means we can tell you not just what the rules are, but what the council has actually approved and refused recently.
- ✓GPDO rules applied correctly. The rules have edge cases — the 50% curtilage coverage rule, the Article 2(3) designated land reductions, the Class B roof space calculation. Our rules engine runs through all of them and shows you which specific rule passes or fails for your project.
Ready to check your project?
2 minutes. Free. No signup. Instant verdict.
Start the checkerWhen an online checker isn’t enough
An online checker is the fastest way to get a preliminary answer, but it has limits you should know about.
- ⚠Listed buildings. Any external alteration needs listed building consent regardless of size. An online checker can flag this, but the actual consent process requires professional heritage advice.
- ⚠Borderline cases. If your project sits right at the edge of a GPDO limit (say, 3.9m deep on a terraced house, or 49 m³ of loft space), the answer depends on exact measurements and interpretation. Apply for a Lawful Development Certificate to remove the ambiguity.
- ⚠Complex conservation area rules. Some conservation areas have specific Article 4 Directions that strip additional PD rights on individual streets. We capture these where they’re published on planning.data.gov.uk, but councils don’t always publish them there.
- ⚠Historic extensions. PD rights are cumulative. If a previous owner built an extension, your remaining allowance may be smaller than the checker estimates. Check your property’s planning history on your council’s portal.
For any of the above, the right follow-up is a Lawful Development Certificate application (legally binding confirmation from your council), a pre-application advice session with the council, or a conversation with a planning consultant for complex cases.
What if the checker says I need planning permission?
If your project falls outside permitted development, you’ll need to apply for planning permission. The householder application fee is currently £258, and the council has a statutory target of 8 weeks to decide. What the checker can’t tell you is whether your application is likely to get approved — that depends on the specific design, the constraints at your address, and recent decisions the council has made for similar projects nearby.
Get your odds — £9
Approval probability + nearby comparables + refusal reasons
Our £9 Full Report layers real recent decisions on top of the free check. You get a personalised approval probability for your specific property, the 5 nearest comparable applications within ~300m of your address, the most common refusal reasons for your property type, and a concrete action plan. Delivered as a PDF.
Frequently asked questions
Is the planning permission checker free?
Yes. The free 2-minute check on whatcanibuild.co.uk returns an instant verdict — whether your project is permitted development, whether it needs full planning permission, and which constraints at your property are relevant. There’s no signup, no email required, and no hidden fees.
How accurate is an online planning permission checker?
Our checker applies the same rules the official General Permitted Development Order 2015 lays out, using live constraint data from planning.data.gov.uk, the Environment Agency, and the relevant councils. For most straightforward projects on unconstrained properties, the verdict is reliable. For borderline cases — listed buildings, complex conservation area applications, or projects near the permitted development limits — an online checker is a starting point, not a substitute for professional advice or a Lawful Development Certificate.
What data does the checker use?
We query live constraint data for your exact postcode: conservation area boundaries, Article 4 Directions, listed building records, Tree Preservation Orders, flood zones, Areas of Outstanding Natural Beauty, National Park boundaries, World Heritage Sites, and green belt. Then we apply the GPDO 2015 rules for your specific project type and property type.
Which councils does the checker support?
We cover 70 councils across London, North West England, and Oxfordshire. If your postcode is outside these areas, the checker will tell you during the assessment. We’re adding new councils as we scrape their planning portals — join the waitlist in the tool to be notified.
Do I still need to apply for planning permission after using the checker?
If the checker says your project is permitted development, you don’t need to apply for planning permission before building. However, it’s highly recommended to apply for a Lawful Development Certificate (LDC) afterwards to get official confirmation from your council — this becomes important when you sell the property. We generate a free LDC application pack for you. If the checker says you need planning permission, the next step is to decide whether to apply or redesign.
What if I get a different answer from my council?
Planning law has grey areas, and officers sometimes interpret the GPDO rules differently from each other. Our checker is strict about the national rules but cannot predict how a specific officer will read a borderline case. For certainty, apply for a Lawful Development Certificate — it’s legally binding and forces the council to give you a clear yes or no.