44 C O N T E X T 1 6 2 : N O V E M B E R 2 0 1 9 The Generator Building at Stow Maries The Generator Building, looking towards the Officers Mess SOPHIE GODFRAIND Historic steel-framed windows Rare steel-framed windows contribute greatly to the historic significance of their modernist buildings. With the right advice and skilled workmanship they can be given a new lease of life. All too often the heritage values of steel win- dows are overlooked, and they are dismissed as substandard and not worthy of conservation.Yet historic steel window frames belong to a specific era in architectural development, contributing to the historic significance of those buildings in which they are found. Production of mild-steel window frames start- ed in the second half of the 19th century, but it was in the aftermath of the first world war (when there was a severe shortage of timber) that they became the glazing of choice for modernist architecture. They were used for everything from shop fronts and offices to council houses, and could even be found in utopian built com- munities such as Hampstead Garden Suburb. They could be mass-produced, making them more affordable, and their sleek lines allowed in more light; they were ‘modern’ and offered secu- rity. Several companies produced steel windows, although one in particular – Crittall Windows – dominated the market.The Crittall name is now synonymous with steel windows. Some window elements, especially the brass window furniture, may bear the maker’s stamp. Steel window frames were either riveted and tenoned, or welded together. Glazing bars often consisted of T-shaped or other simply moulded sections, with the glass held in place with clips and sealed with putty. Longer-lasting hardwood and metal beading was used to seal the joint between glass and frame on later windows. Window furniture was usually brass. The frames were secured into their openings using screws (when the window surround was made of wood), or metal lugs bolted on to the frame and inserted into the mortar joints of the wall, or nails fixed in the bedding mortar. To prevent corrosion, steel windows had to be painted and regularly maintained. Galvanising was introduced in 1948 and became manda- tory for steel windows in 1956. From then on, a painted finish became a matter of aesthet- ics rather than necessity. Shortly afterwards extruded aluminium became a more popular choice for window frames, given its light weight, durability and ability to be extruded into very complex sections.The use of mild steel declined.