8 A cost plus contract is one whereby the builder charges the proprietor the costs the builder incurs for labour and materials, whether supplied directly by the builder or by parties with which the builder sub-contracts, and a fee which is either an agreed fixed amount or an agreed percentage of the payments, as occurred in this case, which may be, and was, in the present case, capped at a certain amount. The fee is to cover overheads and profits. Relevantly, this contract makes no provision for any additional payment: clause 1 of the Contract. A difficulty for the proprietor, which may arise under such a contract, is that whilst it is aware of the general costs payable to the builder or to parties to whom or which the builder may sub-contract certain of the works, it has little control over the costs incurred, particularly in respect of labour hours expended or the quantity of materials actually received and used on the job. In respect to sub-contractors the builder will, usually, pay them either a negotiated lump sum for the whole of the work sub-contracted or, in the case of day labour, a fixed hourly rate. In either case, the lump sum or the hourly rate will include the sub-contractor's profit margin. Where the day labouring sub-contractors are providing their labour as individuals and not through corporate structures, the builder may also be obliged to pay certain on-costs, such as workers' compensation insurance premiums all of which will be recoverable as part of the cost of the works.