477. Express or implied contract.

If the employer has entered into an express contract, whether oral or in writing, with the architect or engineer, the remuneration of the latter will necessarily be governed by the terms of that contract. If the architect or engineer enters into an express contract for a lump sum with the employer, he cannot charge an additional fee for extra work undertaken within the scope of that engagement by him unless the express contract is discharged and a new contract made1.

Where no express contract has been entered into as to the terms of the employment of an architect or engineer,