Sill with detachable water drainage trough for high differential pressure performance

A sill assembly for a door or window frame, comprising:

• an elongate sill body defining a catchment tray and one or more passages extending from the catchment tray outwardly through the sill body toward an exterior margin of the sill body to an outlet, the passages allowing water to drain from the catchment tray and out of the sill body through the outlet;
• and
• an elongate drainage trough detachably mounted to an underside of the sill body adjacent the exterior margin of the sill body, the drainage trough depending downwardly from the exterior margin to define a reservoir that is positioned to receive the water draining from the outlet of the passages, the drainage trough having one or more weep holes that allow the water accumulating within the reservoir to drain from the drainage trough, the drainage trough being detachably connected to the sill body so that the outlet of the passages is exposed when the drainage trough is not attached.