Roofs for Farm Buildings. 131 



coverino^ in or near large towns. His experience of it had been 

 such that he had determined never to use it again ; and he 

 thought it worth while for those who were constructing roofs of 

 that description, to be careful how they employed that material 

 for roofing in a humid climate, and Avhere coal is used for 

 fuel." 



But though this advice applies to all iron covering, we must 

 make a modified exception in the case of corrugated iron, which 

 decidedly forms the cheapest of roofs (in its first cost), and, 

 therefore, under special circumstances, may be applicable. 



The advantage claimed by its supporters are (1) strength, 

 (2) lightness, (3) cheapness, (4) portability, and (5) simplicity 

 of construction, and there is no doubt that in some measure 

 these qualities are rightly applied, for the arched form in which 

 corrugated iron is used does away with the necessity of any 

 framework beyond a few iron ties to keep the covering in its 

 circular form ; it has a light appearance, and can be readily 

 fixed to spans not exceeding 35 feet. 



Fig, 38, on Sheet 8, exemplifies this statement. The cost of 

 this roofing will be found to be 3Z. 05. per square of roofing. 

 These figures, however, should not be taken as representing the 

 actual cost, as it is necessary, in order to preserve corrugated 

 roofing, to paint it frequently. 



Still we can believe, that with such a difference of first cost 

 it may be advantageously adopted in situations free from damp 

 and Aapour, and where durability is not of the first importance. 



COXCLUSIOX. — Such being the inferences which we have 

 deduced from our experience, which the different examples of 

 roofs given in this Essay will support, it is only necessary 

 here to repeat, briefly, that timber-framed roofs are the best 

 and most economical for spans not exceeding 30 feet ; that 

 directly the width of 30 feet is reached, a judicious introduction 

 of iron into the truss reduces the cost, and by giving superior 

 lightness, improves the roof; and that iron alone can only be 

 emploved for the covering of agricultural buildings in very 

 exceptional cases, and never economically for the framework. 



22, Whitehall Place, Westminster. 



K 2 



