Frame: The horizontal and vertical members of a door or window unit which surround the sash, are used to secure the door or window unit into the rough opening and to the building, and/or to which the hinge and lock strike hardware are normally attached.
Head Jamb: The top horizontal member
Side Jamb: the vertical side members
Sill: The bottom horizontal member
Did you know: The word “sash” is derived from the French word “chassis” which means frame.
Legislating Frame Construction
Two pieces of English legislation affected the appearance of sash windows in London. They were imposed because exposed sash boxes were seen as a fire risk.
The 1709 Building Act stated that sash windows had to be recessed 4″ back from the outer brick-work or masonry. The 1774 Act required the sash windows box frame to be set behind the brickwork, so that only about an inch of the sash box was visible from the outside.