^This. If they are keying new ceiling joists into your party wall then they absolutely need to have a party wall agreement and surveyors (to inspect yours and theirs) prior to work starting. I think you need to speak to them ASAP if this is the case.
^This. If they are keying new ceiling joists into your party wall then they absolutely need to have a party wall agreement and surveyors (to inspect yours and theirs) prior to work starting. I think you need to speak to them ASAP if this is the case.