‘Strata’ can be an ambiguous term to use because it is not clear whether you mean the managing agent or the OC. The mediation would be between you and the Owners Corporation (OC), which may be represented by the strata committee unless they have engaged the managing agent to represent them.
It seems that you would have a claim against the OC and then it would be up to the committee to work out whether they can claim for reimbursement from the contractor, or the contractor’s insurance or the OC’s insurance. It is not your problem if the committee can’t recoup its costs from one of those sources and has to fund it from its cash reserves.
Since all owners are members of the OC, I can see some justification for informing the members of the OC that they are involved in a dispute requiring mediation.