Can I stop my neighbours using their flat roof as an unofficial terrace?

I live in the ground floor flat of a Victorian terraced house. The house next door is also split into two flats and there is a rear extension to the ground floor flat with a flat roof. 

The new tenants of the upstairs flat have started climbing out of their window and using the flat roof of the downstairs extension as a terrace. They pull out stools and sit there during the day and at night, and they can see right into our windows and our garden. 

I complained to the council but it said that planning permission is not needed to sit out on an existing roof, is that true?

MailOnline Property expert Myra Butterworth replies: I am sorry to hear about your situation as it seems to be causing some disturbance.

Anyone living in a built-up area may well have experienced something similar or know someone who has.

But while it may seem like a harmless activity to those using the roof, they may not be aware of the issues it is causing, not least to their own safety.

We spoke to a planning expert about the dangers and whether planning permission may be required to use the roof as a terrace. 

Regular use of a flat roof as a terrace is a change of use and therefore requires planning permission

Martin Gaine, a chartered town planner, replies: The pandemic taught us the value of outside space, and I sympathise with your neighbours’ desire to make use of the flat roof outside their window as somewhere to sit out, socialise and enjoy the sun. To them, climbing out of a window to sit on a couple of stools is not a big deal.

But the flat roofs over ground floor rear extensions are not usually suitable for use as roof terraces or balconies because the people sitting on them can look down over neighbours’ gardens and back into neighbouring windows. 

On top of that, noise from several people on a terrace on a quiet summer night can also cause disturbance. For these reasons, the planning system is generally quite hostile to informal roof terraces on standard terraced or semi-detached houses.

In my experience, councils are usually quick to take action against unlawful terraces, so the response from your local council seems odd. 

Regular use of the flat roof as a terrace is a change of use and therefore requires planning permission. 

Although no physical development has taken place (they have not put up railings to enclose the terrace and don’t even leave the stools out there permanently), the use is still unlawful.

This unofficial roof terrace may also be dangerous. The roof was probably not designed to hold their weight and the absence of railings around the edges makes it unsafe. Since the roof is over the ground floor flat’s extension, the new tenants next door are probably trespassing by climbing onto it.

The simplest solution may be to have a quiet word with them to explain the problems associated with their use of the roof. It is possible that they will just stop using the roof once they are made aware of the problems of doing so. 

If that fails, their landlord (the owner of the neighbouring first floor flat) may be able to take action. The freeholders of the building will also have some authority to act if the use of the flat roof is a breach of the flat’s lease.

Martin Gaine is a chartered town planner and author of ‘How to Get Planning Permission – An Insider’s Secrets