In the middle of the 1600s, a change in architecture, coupled with an improved availability of glass, saw the development of a new form of window - the vertical slider. As time progressed, window styling reflected the progress in glass manufacture and the relevant costs and taxation of glass. In the early Georgian period, to meet the proportions of larger windows, timber glazing bars - or astragals - became an important feature of window design. Glazing bars slowly became thinner, and at the same time, the cost of larger pieces of glass reduced, allowing fewer glazing bars.

Windows initially were positioned flush with the front face of a building. This style can still be seen, mainly in the countryside. An analysis of the great fire of London showed that exposed timber was a major contribution to the spread of the fire. The London Building act of 1709 decreed that all windows be set 4" back from the outer brick-work or masonry. In 1774, to further reduce the risk of fire, the box containing the cord and weight mechanism, previously exposed, was required to be set behind the masonry and this is the most commonly seen today.

Early in the 18th Century, the standard glazing pattern of the Georgian window developed. This design, six panes over six panes, remained in use even after the arrival of larger panes of glass in the 19th Century

As astragals were reduced still further, more loadings were put on the meeting rail of a window's top pane. A simple corner joint was unable to transfer the weight of the glass to the verticals. The result was a need for a fully supported joint, and hence horns or ‘joggles’ were introduced. Joggles are often fitted to the lower sash, inside the house where they serve no purpose other than decoration.

The earliest sash windows were mainly constructed of oak. Later, imported Baltic softwoods became widely used for sash windows. However oak and, later, mahogany, continued to be used up until recent times. In most work, oak was used for window sills, the rest of the window being constructed of soft wood, which remained the common practice from the mid-18th Century until the Second World War.

Late in the 19th century the smaller Victorian terraces we are familiar with, used the sash window.