The main risks
An injunction. A neighbour can go to court to stop work until notice is served and the process followed. A builder standing idle costs money, and the court can order you to pay legal costs.
Damage claims without a baseline. With no schedule of condition, any crack in your neighbour's house can be blamed on your work, and you have no record to show otherwise.
Losing the Act's rights. The Act gives you rights you would not otherwise have, such as cutting into a shared wall and getting access to next door. Without notice you may be relying on rights you do not have.
Problems when you sell. Buyers' solicitors often ask whether party wall matters were dealt with. A missing award can raise questions.
If you have already started
Stop the notifiable part of the work and serve notice now. It is better to deal with it late than not at all. Explaining honestly to your neighbour often goes a long way.
If your builder says you don't need one
Builders are not always right about this. The duty is yours, so check for yourself, ideally with a surveyor.
Where this comes from in the Act
- Section 3: Party structure notices
- Section 6: Adjacent excavation and construction
- Section 7: Compensation etc.
Links go to the official text of the Party Wall etc. Act 1996 on legislation.gov.uk.