Contract Works insurance covers the works themselves and in general ‘new works and/or the materials’.
If this cover type is being considered for purchase, it is more than likely that there is a Contractors Combined policy in place. Whilst Contract Works insurance can be purchased in isolation, it would certainly be a good idea to investigate if the existing policy can be extended to accommodate additional requirements.
In the event that the relevant contract motivating an interest in this cover type is complex, a policy in isolation may well work out to be the most applicable cover solution.
A Contract Works policy will cover the works but not the existing structure. Generally, in the event that anything happens to ‘new works and/or the materials’ before completion, the contractor will be held responsible. This situation will of course be dependent upon contractual obligations and agreements arranged prior to the commencement of works.