CONSTRUCTION. 31 



strengthened by the ceiUng joists bemg secured to the foot of 

 the rafters. 



For roofs from 20 to 30 feet span, a king-post and principal King-post 

 rafters are required, which, together with the struts, form what ^°°^^- 

 is known as a truss, or principal, and sustain the purlins in a 

 longitudinal direction about every 10 or 12 feet, and upon 

 which, in their turn, the common rafters are supported, as 

 shown on Plate 35. Above this span it is usual, if timber is Queen-post 

 employed, to use a queen-post roof. ^^^ ^* 



The thickness of the tie-beam for the roofs of lofts and Duties of tie 

 stables varies with the purposes it may be called on to fulfil, but ^^"^^' 

 in wood is rarely made so light as to perform its duties as a tie 

 cnly. It has often to carry the weight of shafting or of a ceiling, 

 and to withstand the effect of machinery in motion, as shown 

 on Plate 48 ; or it may have to support the bales and the poles 

 from which they are suspended, as shown on Plate 35 j or, 

 through the heel posts, may have to resist the shocks from the 

 vagaries of a kicking horse j it may also have to carry the floor 

 of a loft. 



A case is illustrated on Plate 41, where the members of the Provisional 

 roof were made of extra (provisional) strength, with a view to niembers^ 

 the conversion of the buildings into fitter's shops for the 

 introduction of steam tramways. 



The best accommodation for the storage of fodder, when it Loft in roof, 

 is considered desirable to utilise the space in the roof for the 

 purpose of a loft, will be found in the method of construction 

 illustrated on Plate 43, Fig. 2. 



The design for the open roof on -Plates 34 and 35, and Open roofs, 

 that also on Plates 40 and 41, have both been found successful 

 examples in practice. The interior of such roofs may be pre- 

 served and kept wholesome by being wrought and painted, or 

 left rough and well-sized and limewhited. 



The somewhat complicated construction of roof shown in the Gabled 

 first of these designs has two gables at right angles with the ^°°^^- 

 longitudinal section of the king-post r«of, for the purpose of 



