Neighbours Foundations and Party Wall Act

[Rufus200]

Doing an extension which is within the 3m of next doors detached house but party wall act says you only need an agreement if you are digging deeper then your neighbours foundations.

How do you know how deep your neighbours foundations are???

When they did the test hole to see how deep to dig ours, they saw how deep our neighbour's foundations were. Though we are a terrace and she had an extension too so was a bit easier to see...

Building inspectors had to approve how deep our builder had to go. Think usually, unless there is a history of poor stability of land, they will find your foundations and assume NDN is the same.

We didn't go below our neighbour's foundations but were within the 3m and she requested (council also advised) that we get a survey certificate.

It cost us about £500 but I'm glad we did as it gave us both piece of mind. Would quite have liked the cash though...

Maybe call the building control department and ask how they would like you to proceed?

Over time building regulations have required foundation to be deeper so if the neighbouring house is not a new build it's highly likely that their foundations will be lower than the foundations required for your new extension so the party wall act will apply. I think if you are within 3m or your neighbours you should get a surveyor to assess.