130 Roofs for Farm-Buildings. 



Here the boards are laid upon the purlins, and the principals 

 are 10 feet apart. The cost of these several examples, including 

 the covering as mentioned in the preceding examples, will he 

 found to be as below : — 



Cost of Roofing 

 complete per square 



Sheet 7, : (lo x lo). 



Fig. 28 £7 8 8 



„ 29 7 13 9 



„ 30 8 4 



„ 31 .. ■ 8 10 8 



„ 32 8 7 4 



„ 33 9 10 



These figures, when compared with the preceding examples of 

 timber-framed roofs, prove that it is not economical to resort to 

 iron framework in small spans. Of roofs of 24 feet span, 

 inside measurement, two examples are given. Fig. 35 is con- 

 structed of rolled "^-iron for the rafters and purlins, and of flat 

 rolled iron for the ties and struts. The cost of this example will 

 be found to be 6/. 10a\ 6f/. per square of roofing. Fig. 34 is the 

 more expensive example, and is constructed of rolled "y-iron for 

 the rafters, purlins, and struts, and rod-iron for the ties and 

 bolts. The cost of this roof will be found to be 6Z. 15,s. Id. per 

 square of roofing. For roofing of yards and large spaces two 

 specimens are given on Sheet 8. Fig. 36 represents an arrange- 

 ment where rolled "y-iron is employed for the rafters and struts, 

 and round iron for the tie-rods. The principals are placed 6 

 feet apart, purlins are dispensed with, but, as in a preceding ex- 

 ample, boards stretch from truss to truss. The cost of this roof 

 is y/. 2^. \{)d. per square of roofing. The second illustration, 

 Fig. 37, is of cheaper construction: — three spans in this instance 

 taking the place of two as in the previous case. The cost of this 

 roof will be found to be 8Z. 11.9. lOd. per square. 



Many of our ablest civil engineers have used iron framework 

 for the roofing of railway stations, but as these roofs are generally 

 of large span, and the object for which they are used sanctions 

 more than ordinary outlay, they form no precedent for adoption 

 in agricultural buildings. 



Mr. Hawkshaw, the President of the Institution of Civil En- 

 gineers has thought it necessary to warn his brother engineers 

 against the use of iron, even when galvanised, for roofs. It 

 should be observed that his observations have reference more 

 to covering than to framework, but they are so decided that they 

 cannot be discarded from consideration. He says, " the result of 

 not more than four years' wear was such as to convince him 

 (Mr. Hawkshaw), that galvanised-iron ought never to be used for 



