JCT 6.5.1 Insurance
If you are refurbishing or extended your building or erecting a new one, you need to ensure that the main contractor holds “contractors all risks” insurance for the project, and that they, plus any other contractors, also hold Public Liability insurance or, for any professionals you may appoint (such as an architect or surveyor), professional indemnity.
However, there is a further insurance that should be considered if there is any danger that a neighbouring property may suffer any damage due to your works. This is called "JCT 21.2.1" under the from the clause 21.2.1 of the JCT '98 Standard Building Contract or clause JCT 6.5.1 under the JCT 2005 Standard Building Contract (sometimes referred to JCT minor works contract) after the relevant clauses of the Joint Contracts Tribunal.
If a neighbouring property subsides or collapses due to the negligence of the contractors) or architect, then a claim would be directed to them (and do make sure you have evidence of their insurance in writing). The contractor needs to hold Public Liability insurance and the Architect will need Professional Indemnity insurance to deal with these insurance claims.