This will largely depend on your location. You will find that certain areas have different setbacks based on the use of the building. We recommend that you check with your local council or take a look at the Goverment's Planning Portal.
You must notify your neighbour if you want to:
- Build on or at the boundary of your 2 properties
- Work on an existing party wall or party structure
- Dig below and near to the foundation level of their property