332. Ultra vires certificates.

The certificates of architects and engineers are only conclusive as to matters entrusted to them, and if the certificate is ultra vires as to any matter it is to that extent not conclusive1. Thus, it may be conclusive as to quantity and not as to liability, or vice versa2.

Again, if there is no power in the contract to vary the work to be done, a valid certificate cannot be given for work done at variance with the contract, even though the variation was made on the instructions of the architect, and is of equivalent value to that which should