Abstract: A sill assembly for a door or window frame includes an elongate sill body with a water catchment tray and one or more drainage passages extending from the catchment tray to an outlet, and a drainage trough mounted to an underside of the sill body and depending downwardly therefrom to define a reservoir that receives water that drains from the outlet of the drainage passages. The drainage trough includes weep holes which restrict outflow from the reservoir and is detachable from the sill body, which facilitates the manufacture of the sill assembly in different configurations to suit site requirements.