Mechanical Structure of Sliding Windows

Identification

• As their name implies, sliding windows contain one or two moving sashes that slide either vertically or horizontally. Vertical sliding windows are known as double-hung windows, while horizontal windows are known as gliding windows. For example, some windows feature only a bottom sliding section that moves up and down over a stationary top section. Others feature two sliding sashes that overlap within a single frame.

History

• During the late 17th centry, early sliding windows contained thick, wood members that divided sashes into tiny panes, according to the Historic Scotland publication “Sash & Case Windows: A Short Guide for Homeowners.” As high quality glass became more accessible in the mid 1700s, sliding windows featured larger window panes and thinner sash grills. Sash windows during this period were made with high quality crown glass, which projected a rippled surface when facing sunlight. Different types of glass and grill patterns were introduced, and larger, heavier glass became more common throughout the 19th century. Today, sliding windows feature sashes that move in tracks and are held in place by snap-in members or individual muntins.

Modern-Day Structure

• Like their predecessors, modern-day sliding windows also include muntins or grills. These are the the thin members that separate glazings into small, individual panes. The lower and bottom (or right and left) sashes are divided into top and bottom rails, and stiles. Stiles are the side portions of the sashes. Surrounding the sliding windows is the exterior and interior casing or framing. The side and head jambs comprise the window frame, and are located inside the casing. Locking mechanisms, also called sash locks, secure and lock the sashes in place.

Materials

• Generally, window frames and sashes are built from wood, aluminum, vinyl or composite materials such as polyvinyl chloride (PVC). Though wood offers optimal insulation against outside elements, vinyl and metal are stronger and less prone to erosion. As a result, manufacturers often clad vinyl and aluminum framing and sashes with timber. Ball bearing rails, rollers, interior profiles, connector profiles and closing mechanisms are typically made from metals such as aluminum. Other materials such as silicone, adhesives and brass are used for the glazings in sliding windows.

Features

• To prevent heat transfer and leakage, modern sliding windows are often built with insulating glass panes that are watertight and rigid. Moreover, some manufacturers include draining chambers that capture and channel water vertically, and improve the window's waterproof capabilities. This steel chamber can contain draining foam PVC elements, which reduces wind pressure and provides structural support for bearing loads.