Quasi contract (or quasi-contract) example

A school district and a roofing company enter into a contract in which the roofing company agrees to install a roof on a school pursuant to an architect's instructions. The roofing company installs the roof and allegedly performs additional work (of which the architect is aware) outside the scope of the contract. The roofing company is allegedly paid for the roof's installation, but not for the additional work. If the additional work is, indeed, outside the scope of the contract, the roofing company has a quasi-contract cause of action and may recover under a theory of quantum meruit.