12% of homeowners who have completed a major upgrade or extension either failed to obtain the proper planning permission or didn’t realise they had to do so says EXP UK head Adam Day.

Research carried out by the estate agent platform revealed 21% did so knowingly, with the main reason being that they were confident they wouldn’t be found out.

For those who are, the consequences can be serious – the homeowner can be prosecuted, forced to demolish the offending structures and return the building to its original state.

This makes buyers nervous and separate research by Directline Insurance highlights the negative effect this can have on the sales process.

Collapsing deals

Without planning permission, 28% of chains collapse and 27% of buyers will pull out of a deal, although 29% of the time it leads to no more than a price reduction.

However, it is not just about collapsing deals, if the sale does proceed, it can also cause substantial delays and problems with buyers’ mortgages.

There are a number of options which can help ease the deal through.

EXP says that if the structure or works have been in continuous use for ten years without being challenged (or four years for breaches that occurred before 25th April 2024) the vendor could obtain a lawful development certificate.

This allows them to keep the renovations as they are, even if they would have failed to obtain planning permission via the normal channels.

A vendor can also take out indemnity insurance or apply for retrospective planning permission.

What’s quite astounding is that a notable number of those undertaking a major renovation are doing so without ensuring the proper planning permission is in place”.

Head of EXP UK, Adam Day, adds: “Homeownership doesn’t come cheap and we’ve seen house prices continue to climb in recent years.

“So, it’s understandable that a good proportion of homeowners have undertaken major renovation projects on their existing homes, such as extensions or conversions, in order to maximise space.

“What’s quite astounding is that a notable number of those undertaking a major renovation are doing so without ensuring the proper planning permission is in place”.