Double-hung timber sash windows first appeared in London in about 1670. They were an English invention and proved the most popular form of window for over two centuries. Early eighteenth century windows have thick glazing bars and visible sashboxes. The 1774 London Building Act required that the sash boxes should be covered externally by brickwork. Late eighteenth century sash bars are thin and usually of lambs’ tongue section. The usual eighteenth century arrangement comprised six panes over six panes, whereas in the mid-nineteenth century it comprised two large panes over two.
Double hung sashes with concealed sash boxes with or without glazing bars are the prevalent type of windows in the listed buildings in Covent Garden. Georgian sashes do not have ‘horns’ (the little scrolled brackets at each end of the bottom rail of the upper sash intended to strengthen the frame). These were a feature of Victorian sashes made necessary by the use of heavier larger panes of plate glass rather than thin small Crown glass of Georgian sashes.
Old window sashes are of historic interest and should be kept and repaired wherever possible. But when renewed, or replaced, the mouldings and proportions should be copied exactly from authentic patterns. Grants, and advice, for the restoration of external joinery are available from:
The London Division of English Heritage,
1 Waterhouse Square, 138-142 Holborn, London EC1 2ST
Tel: 020 7973 3000
Crown glass can be obtained from:
The London Crown Glass Company,
21 Harpsden Road, Henley-on-Thames, Oxfordshire RG9 1EE
Tel: 01491 413227
Fax: 01491 413228
Verre Royale is the closest approximation to genuine Georgian glass. A firm which specialises in the careful restoration of old sash windows is:
Sibley & Son, The Grange, The Mayford Centre, Smarts Heath Road, Woking, Surrey GU22 OPP.
Tel. 014862 24854
Fax: 014862 20064