My neighbours are extending in to their basement. Recently the drilling work has intensified and I’ve noticed a crack in the hallway. Should they be using a lower level of force in the drilling i.e. so the house is not shaking and creating cracks as they go?
You don’t say whether there is a party wall award in place but if there is the appointed surveyor(s) should have considered ways in which they could reduce the risk of damage. A typical safeguard would be to prohibit the use of percussive tools (such as hammer drills, kangos etc.) on works directly affecting the party wall. Vibration can carry from works on other parts of the property, over which the party wall surveyors have no control, to the party wall and cause vibration but that would be less intense than work directly to the party wall.
Even if you consented to the works and there’s no party wall award you may want to suggest this safeguard – it is in the building owner’s interest to avoid damage.
The Act gives you the option of either allowing the building owner (or their contractor) to make good the damage or receiving a payment in lieu. This applies whether or not there is a party wall award and if there is a dispute relating to that damage you have the right to appoint a surveyor. If the heavy work is ongoing it may be best to deal with this later in case there is further damage.
If there is a party wall award in place which prohibits the use of percussive tools but it is being ignored it is more a matter of enforcement – I would suggest that you raise it via your appointed surveyor in the first instance but if that doesn’t work the only remedy is an injunction (although I would recommend you seek legal advice before going down that route).