Box sash wooden windows are made with a hollow section within the window frame that holds the sash weights. The sash weights are attached to a sash cord that is in turn connected to the sliding window pane. Commonly the sash weights in the weight and pulley system are made from lead, although more recently some sash weights are made from steel. The sash cord is manufactured from braided cotton that has been pre-stretched and has a polished finish to prevent wear. Some of the newer sash cords are made from other materials and man-made fibres such as polypropylene and nylon for increased abrasion resistance.
Box sash windows can be made from various different softwoods or hardwoods. Some woods used to manufacture box sashes are Mahogany, American white Oak, Pine and European Redwood. The timber used to manufacture sash windows should be vacuum pressure treated with preservatives and wax resins for maximum protection. It is also advisable to make sure wooden box sash windows have been treated with an insecticide and fungicide. This will prevent damage to the box sash windows from wood-boring insects and protect against wood rotting fungus. Usually, even box sash windows manufactured from pressure treated softwood will still have hardwood used for the window sills.
The traditional Georgian sash window would have six panes of glass in each section of the sliding sash window. Therefore ending up with a window containing a total of four panes of glass down by three panes of glass across. This configuration of the window panes is not compulsory for sash windows and sashes are available in many different styles and designs to suit the particular property. During the Victorian era, many properties had bay windows fitted with sliding box sashes. Other Victorian style windows were Oriel windows and Queen Anne windows.
Windows are available in a variety of finishes from stained or varnished wood to gloss paint in a variety of colours. Hardwood and Softwood timber framed sash windows can be stained or varnished to enhance the natural grain and colour of the timber. Box sash windows requiring a painted finish should be treated with a quality primer or undercoat first before the top coat is applied.
New and replacement wooden framed box sash windows are now available with double glazing for maximum energy efficiency. While still made from traditional timber and manufactured in keeping with the facade of the original building the property owners can still benefit from double glazing. The double glazed box sash window can provide soundproofing and thermal insulation for the period home.
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