Our survey of homeowners and analysis of government statistics show that you need to do your homework and allow plenty of time to navigate the UK planning permission system.
We asked more than 2,000 homeowners who have carried out projects that needed planning permission about their experiences1. The good news is that 80% of them said they didn't experience problems.
However, for the hundreds of homeowners who did run into difficulties, timescales topped the list of troubles.
Of those who'd had problems with planning permission, 44% said they'd underestimated the amount of time it would take, sometimes delaying home improvement projects by weeks or even months.
Having to change plans after work had already started was the second most common complication, highlighted by 23% of those who'd experienced planning problems.
Another regular headache for homeowners was underestimating the cost of the process, followed by failure to apply at all for planning permission when it was needed.
Other issues that homeowners said they had experienced include:
Here are just a few of the stories people told us about their planning permission woes.
Planning authorities in the UK have statutory time limits to deal with planning applications, which vary depending on where you live.
These deadlines can be extended if the council gets written agreement from the person applying or if additional work is needed, such as an Environmental Impact Assessment.Extensions to the deadline are relatively common, so you need to bear in mind that this could affect your schedule.
We've analysed data reported by local planning authorities across the UK between April 2018 and March 2019 to find out how many applications are actually approved within the statutory time limit or within agreed extensions.
Across the country as a whole, only 64% of non-major decisions were made by local authorities within the eight-week statutory deadline3 . You were most likely to get a verdict within that time limit if you live in the north east, where 70.7% of decisions hit the target, whereas in the south west the figure is 60.4%.
But many decisions that took longer than eight weeks did so because the councils had agreed deadline extensions with the applicants. A total of 91.6% of non-major decisions were made within either statutory or agreed limits.
Just 69.7% of non-major decisions were made within the statutory eight weeks during 2018-194.
However, many councils here also agreed with applicants to extend the time limit, and 88.5% of decisions were made within statutory or agreed limits.
Homeowners here are more likely to have a long wait. Not only does the country have the longest statutory deadline at 15 weeks, but councils processed just 50.9% of local development applications within this time frame5.
Decision times varied quite widely between the different local authorities, so it's worth looking at how yours has performed to get a clearer idea of how long your application could take.
Figures have not yet been published for all local developments in 2018-19. But from April to September 2018, about 76% of decisions were made in less than the statutory two months6. The figures available for this period did not give a clear indication of how many were made within agreed extensions.
Applications that didn't need legal agreements took an average of nearly nine weeks. Those that did need legal agreements took an average of about 31 weeks.
Research and preparation are key to avoiding some of the common issues homeowners told us they'd experienced when applying for planning permission.
Although you can't always control factors such as the length of time it takes to decide your application or how much it costs, a bit of groundwork can help you to avoid a nasty surprise.
Don't assume your application will be decided within a few weeks. The more complex your plans or situation, the more likely it is that the deadline will be extended or missed.
There are steps you can take to minimise delays or reduce their impact:
If a delay leads to you losing the contractors you'd hired, you can use Which? Trusted Traders to to help you get your project back on track. All endorsed traders have been through our rigorous assessment process and have signed up to our Code of Conduct.
Ideally, you'll do the groundwork before submitting your application to make sure that it's right first time. Consulting or architects as well as your planning department before applying can help to uncover potential pitfalls that might lead to changes.
But not every project goes as planned and sometimes, despite your best efforts, you'll need to change the build from what was agreed with the planning authority. If this happens you should notify the council as soon as possible to reduce delays to your project.
The cost of planning permission varies depending on the scale of your project, and as the homeowners in our survey found, there can be unexpected additional costs.
To avoid an unpleasant surprise, you should:
Depending on circumstances and the scale of the project, some extensions, loft conversions and balconies can be constructed within permitted development.
If you choose this option, remember to:
As with every part of the planning process, it's best to do your research and get advice from the local authority if you're unsure about what you can do.
1 April 2018 survey of 2,030 Which? members who said they had experience of planning permission. 2 From a survey of 213 Which? Trusted Traders conducted in April 2019. 3 , excluding the Old Oak and Park Royal Development Corporation, the Ebbsfleet Development Corporation and the London Legacy Development Corporation. 4 . 5 . 6 .