What cover would my client have under a standard home insurance whilst works are going on at my home?

Most home insurance policies exclude damage to your buildings and contents whilst work is ongoing. They usually at least require insurers to be advised, when they are, they may either refuse to continue cover, or will impose restrictions and will usually require an additional premium. At the very least, your client has a duty to advise their insurers of any changes to material information regarding their exposure to risk; if works are being carried out at their home, this would class as material information. Therefore, even if there was no specific requirement or exclusion in the policy, they may still find themselves not covered in the event of a claim, should they not give their insurers information about works beforehand and specifically agree with them that they will provide them with cover.