(1)  This section applies to a residential building work contract if the contract provides for a provisional sum or a prime cost item.

(2)  The building contractor warrants the provisional sum or prime cost item has been calculated with reasonable care and skill, having regard to all the information reasonably available when the residential building work contract is entered into, including information about the nature and location of the building site.

(3)  Without limiting the circumstances in which a provisional sum may be taken to have been calculated with reasonable care and skill, a provisional sum is to be taken to have been calculated with reasonable care and skill if it has been, in relation to residential building work, calculated by the building contractor on the basis of –

(a) written advice, in relation to the work, provided by the designer or the owner; or

(b) an amount, in relation to all or part of the work, that is specified in a schedule to a design, or to a tender, that relates to the work.