used as part of the structure of an attic room. With two posts introduced the roof form is known as a 'queen post' truss, which in its simplest form is shown in Fig. 1.8. This particular roof form gave the opportunity of providing a limited living space within the roof. It should be remembered that until this stage of development all roof forms and trusses described had no ceiling and were open to the underside of the rafters and roof covering. To use the queen post roof form as an attic, a floor was needed thus creating a ceiling for the room below.
Ceilings were first referred to in descriptions of roofs in the fifteenth century when they were known as 'bastardroofes' or 'false roofs' and then later as 'ceiled roofs', hence 'ceiling' as we know it today.
The ceiling supports were known as joists or cross beams again being supported by the hard working tie beam between the principals. The construction is illustrated in Fig. 9.2.
Continuing developments of the roof form itself, and demand for even larger spans and heavier load resulted in some relatively complex principals or trusses being developed. One such form was the 'hammer beam' roof, illustrated in Fig. 1.9. Clearly this is not a roof to be 'ceiled', being very ornate as well as functional.
The hammer beam roof is generally to be found supporting the roof over halls in large mansions and of course churches. The roof was framed in such a way as to reduce the lateral thrust without the need for a large and visually obstructing tie beam. The walls onto which such a roof was placed had to be substantial and were
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