Design for the roof over the east and west ranges, February 1790 (1)
The recto of the sheet has a design for a king-post gabled roof over the east and west ranges, with dimensions ('scantlings') of the roof timbers. The roof has purlins resting on the principal rafters, an innovation in roof construction not commonly executed (except in France) before the nineteenth century (D. Yeomans, pp. 141-2). Traditionally, purlins would be butted against the principal rafters so that mortices had to be cut in the principals. Separating the purlins as shown in drawing 25 removed the necessity for mortices in the principals, thus permitting the latter to be reduced in size; and furthermore, the structure was simpler to assemble. This new arrangement required some other structural changes to keep the common rafters even with the eaves while maintaining the roof strength: as in drawing 25, the principal rafters were on a 'bottom' level and the common rafters on 'top', with a pole plate ('poll plate') receiving the rafters at the ends of the tie-beam.
The verso of drawing 25 has a ground floor plan of the stables with the ceiling and roof timbers included in yellow wash. Some of the roof timbers are shown in elevation to indicate their form. The east and west ranges of the stables are one-storey with gabled roofs as drawn on the recto.