To ask neighbour to pause building work and sort out planning permission and party wall agreement before continuing?

[123MyName321]

Semi detached neighbour has just started digging foundations for an extension. Foundations are more than 3 times deeper than our house foundations and within 5cm of our party wall. No party wall notice was served. After speaking to the builders, it also transpires that the extension is large enough to require planning permission, which the neighbours do not have.

We aren't opposed to the neighbours improving their home, but we want to make sure things are done safely and legally.

We would like a surveyor to check that the plans are structurally sound given our house's very shallow (less than 30cm) foundations and we would like to know what the plans are for their extension, as it might end up substantially overlooking our garden.

We would also like them to apply for the required planning permission before continuing their build as I understand an unpermitted structure next door can affect our ability to sell our house.

Are we being unreasonable?

You are not being unreasonable at all . Without it your insurance might not cover you at all . Get legal help asap and call building and planning control asap . Your property can potentially be in danger .

Many many moons ago I worked as a surveyor, and although my memory is hazy, i definitely remember doing party wall work and for the kind of work you’re describing, your neighbours need to hire a party wall surveyor. I’m pretty sure that’s a legal requirement. It covers you both in the event of any damage to your property. A proper condition survey is necessary in relation to your party wall or boundary before work commences.