140 



VETERINARY HYGIENE 



which must be added the necessary roof lights, outlets, ventilators, 

 gutters, &c. 



A roof truss may be composed of wood or steel arranged to form 

 a rigid support for the purlins and covering. The trusses, resting 

 upon the wallheads and set at suitable centres, carry the purlins, 

 to which are fixed the boarding or corrugated iron. 



The various forms of roofs are illustrated in figures 54-56, 

 where the names of the members are shown. It should be noted 

 that the width of the building to be covered, together with the kind 

 of covering adopted, will largely 

 determine the type of roof. 

 For the necessary warmth in 

 winter and coolness in summer, 

 it is emphasised that a roof 

 having either plain or grooved 

 and tongued boarding over its 

 whole surface is most desirable, 

 no matter how covered. 



Roofing composed of steel 

 trusses, wood purlins and 

 boarding, covered with felt 

 and slates, possesses all the 

 qualities desirable for a stable. 

 This form of construction is 

 warm in winter and cool in 

 summer. The covering is dur- 

 able and easily repaired. The 

 steel trusses present the smallest 

 surfaces for the lodgment of 

 dust, and the minimum obstruc- 

 tion to the passage of air and 

 light. The same type of roof 

 with wood trusses comes next 

 in favour. A roof of similar 

 construction, but lighter in its 

 members, covered with one or 

 two thicknesses of bituminised 

 felt or canvas fixed properly to 

 the boarding, is permissible 

 where slates are not available. 

 If cost is a serious considera- 

 tion, a very much lighter 

 structure of the same type, but FlG . 54.-Couple Roofs. 



