Rear Extensions and Party Wall Notices
Do I need to serve a party wall notice if I am building an extension in my back garden. This is a question we often receive. Even if your house is detached you will still need to serve a party wall notice if your foundations will be within 3 m of your neighbours structure. This could be the house but could also include a Boundary wall or even a pathway.
However, the foundation also needs to go below your neighbours foundation for the notice to be necessary. If it's a garden wall or a path or a driveway, you will always be going deep up. If the neighbours house has been built before the mid 70s it is likely that your foundations will go deeper than theirs as well. However, if the house has been built after 1976 the chances are, your foundations will not be going any deeper and you will not need to serve the party wall notice.
The other event that may trigger the need for a party wall notice is if your new wall of your extension will be up to the Boundary. The neighbour cannot stop you building this wall but may want some input. You can also, by means of the party wall notice, request that the wall being built astride the boundary. However, you have no right to this, and if your neighbour dissents or simply does not reply to your notice you will have to build the wall on your own land.