These windows are categorised into 3 primary classes based on the era in which they originate.
Georgian sash window
The Georgian sash window features a 6 over 6 double-hung design.
This means that there are two rows of three panels each in a 6-light sash. The design also introduces small glass panes that are separated by several glazing bars.
Victorian sash window
The Victorian sash window era favours the 2 over 2 grid design. The design incorporates one large glass pane, with the smaller sashes featuring on upper rooms and larger ones on the ground floor.
Edwardian sash window
The Edwardian sash window features a 6 over 2 design, with a multi-pane approach for its sashes. This includes having a single glass pane on the lower sash, and multiple panes on the upper frame.