60 



FAEM BUILDINGS IN SOUTH AFRICA 



up to 12 feet. It is advisable to purchase the iron all of one brand, on 

 account of possible difficulty in fitting sheets of different brands together, 

 due to slight differences in the shape and size of the corrugations. 



By " gauge " of the iron is meant its thickness. No. 24 gauge should 

 be used as No. 26 gauge is very thin, and apt to be penetrated by hail- 

 stones. 



At horizontal joints the plates should overlap each other by at least 

 6 inches, the purlin being placed 1£ inches up from the lower edge of 

 the upper sheet, as shown in Fig. 60. 



The joints running from ridge to eaves should have an overlap of at 

 least 3 inches, or one complete corrugation (i.e. one ridge plus one valley), 

 as shown in Fig. 60. 



Fig. 60. 



Looking at the right hand view of Fig. 60 it will be seen that the 

 plates in the middle of the view overlap those on each side, on the top 

 of these latter plates. Further, the long edges of the plates in the middle 

 of the view point downwards, and so throw off the rain-water and make 

 it less liable to penetrate the joints. This arrangement should be secured 

 in all such joints ; it may be obtained by having upper and lower plates 

 alternately (along the roof), as shown in the right-hand view of Fig. 60. 



The corrugated iron plates are fixed by galvanised iron roofing screws, 

 which are driven into the purlins with a hammer (see Fig. 60). Under 

 the head of each screw two washers are inserted, a lead washer below and 

 a galvanised iron washer above. The screws are inserted in holes 

 punched in the ridges of the corrugations, not in the depressions. Care 

 should be exercised not to punch the holes any larger than necessary to 



