Robin Longbottom spotlights an often overlooked role which was pivotal in the construction of mills

TODAY, very few 18th-century textile mills survive in the South Craven and Keighley area.

Many have been demolished over the years and others altered beyond recognition.

However, a handful remain – such as Brow End Mill (Rag Mill) in Goose Eye, Low Mill in Keighley (now ruinous) and Dale End Mill at Lothersdale.

The three mills conformed to the same 18th-century standard. They are three storeys in height and although they vary in length, they are all 27 feet (nine yards) wide. The rather curious width of 27 feet was determined by the maximum width of the trusses that could then support a roof with heavy Yorkshire stone slates.

Making the trusses and the other timber work was undertaken by a master carpenter, whose role in the construction of mills has been largely overlooked. As opposed to a joiner, who made window frames, doors and generally more refined woodwork, the carpenter tended to concentrate on the heavy timber work associated with buildings. Roof trusses in this period fell into two types, known as a king post and a queen post truss. A king post truss had a central post that supported the apex of the frame and had a maximum span of 24 feet. The queen post truss was a later development; it had two vertical posts to support the frame, and this enabled the span to be increased to 27 feet.

Dale End Mill at Lothersdale, built in 1792, still retains its original roof structure. It was erected on the site of a former corn mill and financed by a consortium of gentlemen – Thomas Chippindale of Stone Gappe, Glusburn; Thomas Wigglesworth of Milton House, Cononley; Richard Croasdill of Marton Scar near Skipton, and Chippindale’s nephew, Thomas Parker, a minor who had joined "by his own free will and the consent of his guardian". However, the consortium also included a fifth man, Edmund Spencer. He was a carpenter from Cononley and his contribution to the enterprise was building the new mill.

The original mill was built to spin cotton, and is now part of a much larger complex. It measures 27 feet in width, 60 feet in length and is three storeys high. The first and second floors were supported on single tie beams, each one the width of the mill, and the roof by queen post trusses. Each truss was first assembled on the ground and the separate timbers marked with Roman numerals. They were then dismantled, and the separate parts taken to roof level and then, guided by the inscribed numerals, the carpenters reassembled them in their final position. The timbers fitted together with mortice and tenon joints and these were then secured by wooden pegs, known as a trennels (tree nails). Although trennels were used at Dale End they were largely obsolete by this time and were being replaced by wrought iron bolts.

The width of the roof truss also determined the size of the early spinning frames. At Dale End, and other mills, the frames were located on the top floor. Here the tie beam was used to carry the mill shafting that powered the machines. The shafts passed through brass bushes that were fitted in bearings known as plummer blocks and these sat centrally on each beam. Pulleys and drive belts then took power to the machines that stood in pairs across the width of the mill. The bolt holes and oil stains where the plummer blocks were once located can still be seen on the beams at Dale End.

The introduction of cast iron columns to support floors and roof timbers eventually enabled wider structures to be built and with the later development of cast iron bracings and steel girders, the once important role of the carpenter declined.