What is a Sill ?

Definition of Sill in Construction
The bottom of a door or window. This piece of framing that will rest on the bottom of the masonry or rough opening. The sill is a descriptive term that normally means the bottom of an assembly. For example the sill plate is the lowest framing member that sits directly on the top of the fop of the foundation wall. The window or door sill can be made of wood, aluminum, vinyl or other synthetic material and is important to the effective closing of the door and window. In many installations the sill of the door or window has an additional weatherproofing application such as a door sweep or a weather stripping material applied. Window and door sills are pitched to the exterior to allow water to drain away to the exterior of the structure and out of the window or door opening.