Planning permission approval rates — I crunched the numbers for every London borough (and 100+ other councils)

[WittyNavyFinch]

I keep seeing threads on here from people panicking about whether their extension / loft conversion / garage conversion will get planning permission, so thought I'd share something that might help.
I've spent the last few months pulling together data from council planning portals — basically every planning decision made across 135 UK councils. Nearly 2 million decisions in total.

The short version: most planning applications get approved. The national average is around 85%. Even in the "toughest" London boroughs, you're still looking at 76%+.

Some things that surprised me:

The council matters more than you'd think. Kensington & Chelsea approves 92.5% of applications. Brent approves 76%. That's a huge gap for two boroughs that are only a few miles apart.

Rear extensions are almost always approved. Across the dataset, rear extension approval rates are above 85% in most councils. If yours is within permitted development limits, the odds are very much in your favour.

The ward within your borough matters too. Within the same council, some wards approve 95%+ while others are below 75%. Your immediate neighbourhood makes a difference.

For anyone mid-panic about their application — the data really does suggest that if you've followed the rules on height, boundary distances, and materials, you're more likely to be approved than not. Obviously every case is different and conservation areas / listed buildings are a different story.

I've put all this into a free tool where you can check your specific postcode — it shows your council's rate, your ward's rate, and what types of projects get approved most often in your area. It's at planninglens.co.uk if anyone finds it useful.

Happy to look up specific councils or areas if anyone wants to know their odds!

Here are the top 5 approval and top 5 rejection boroughs in London :)

It also helps (well in our case anyways) to talk to neighbours first. We had no objections at all, for a small, double extension.

The previous owner had 17 objections, although his plans were bigger and he was an absolute A-hole according to anyone I've met who knew him!

Amazing work. It may be that some boroughs have a different approach to the pre application process.

That's a good point. Neighbour objections are one of the biggest factors in whether an application gets called to committee rather than decided by the planning officer. And once it's at committee, approval rates drop noticeably. The data backs this up too... straightforward applications with no objections sail through, while anything contentious takes longer and has worse odds. Sounds like the previous owner's reputation did him no favours! 😂

Thanks! You're absolutely right that the pre-app process varies massively between boroughs. Some councils are really proactive about steering applicants toward something approvable before they formally submit, which naturally pushes their approval rate up. Others basically say "submit it and we'll see." It would be fascinating to separate out councils that offer free pre-app advice vs those that charge for it and see if there's a correlation. Might dig into that next! Thanks again!

We’ve had 2 refusals despite not having any neighbour objections. The third that was approved received an objection but ultimately we didn’t like the plan that was approved so didn’t build it!

That's really frustrating... and actually a great example of why the overall approval rates don't tell the whole story. 85% sounds reassuring until you're in the 15%! Do you mind me asking which council that was? Some councils have noticeably higher refusal rates for certain types of extensions, and the reasons for refusal tend to follow patterns. Things like overlooking, loss of light, or "out of character with the streetscene" come up again and again. If you share the council I can look up what the most common refusal reasons are in your area.

What prompted you to do that OP? Experience or a love of data?

A bit of both! We were looking into an extension and I was super frustrated trying to figure out what our actual chances were. Every forum post seemed to be "it depends" and every planning consultant wanted hundreds of quid before they'd tell us anything even half useful. The council planning portals are all public data, but they're incredibly tedious to trawl through manually. So I started pulling it all together and it snowballed from there. 135 councils and nearly 2 million decisions later, here we are... sharing it with mumsnet 😅

That's true. We were very lucky and our neighbours on both sides wrote to support our plans (a single story extension to replace a large, failing asbestos-ridden lean-to). We showed both sets (along with the immediate houses across the street- it's a close knit road...) plans early on to make sure they knew what we were doing and why.

Do you gather data on applications withdrawn?

Wandsworth seem to encourage that rather than issue an outright rejection.

And it all still depends anyway: is depends on what the application is for. I've fought a couple of monstrosities and got them rejected. But others go through. Simple applications within guidelines should go through without issues.

Ward stats are meaningless. Each will be decided by the same Planning Officers and Planning Committee(where deemed necessary) for the Local Planning Authority they fall within. Variation would reflect local factors such as Conservation areas, National Landscapes or neighbourhoods with a higher proportion of listed buildings or new builds, which may be more restrictive and require that specific rules are followed, as defined within the NPPF.

Yes, withdrawn applications show up separately in my data. Wandsworth has quite a high withdrawal rate actually, which supports what you're saying.

If the council informally tells applicants "this isn't going to pass, you might want to withdraw and resubmit" then the formal refusal rate looks lower than the real rejection rate.

It's a known pattern with some councils and it does make their headline approval rate look more flattering than the reality. It's one of the reasons the ward-level data is interesting. You can sometimes spot wards where the withdrawal rate is unusually high compared to the outright refusal rate, which hints at a more proactive planning department.

And you're absolutely right that it depends on what the application is for. A straightforward single storey rear extension is a completely different proposition to someone trying to squeeze a three storey side extension onto a narrow plot.

The data I'm compiling is useful for a general sense of your odds, but every application is ultimately judged on its own merits, of course :)

That's a fair point. You're (of course) right that the same planning officers and committee handle the whole borough.

The ward variation isn't about different people making decisions, it's exactly what you've described... conservation areas, listed buildings, Article 4 directions, and the character of the housing stock all cluster geographically.

A ward that's mostly Victorian terraces in a conservation area will naturally have different outcomes to a ward of 1960s semis with no designations. The ward stats aren't measuring planning officer behaviour, they're a proxy for those local constraints. This is actually useful for homeowners, because someone in a heavily designated ward knowing their area runs at 72% tells them something different to someone in an unrestricted ward at 94%, even though it's the same council making the call.

So what I'd say is that the data confirms what you'd expect intuitively. It just puts a number on it.