CHAPTEE VI 



ROOFS, AND ROOFING DETAILS 



The carpenter understands by the word "roof," the timber frame- work 

 which supports the covering of a building. The covering itself may be 

 spoken of as the " roof-covering." 



Eoof-coverings are carried, in the first instance, by a series of frames 

 called principals or roof trusses, which span across the building to be 

 roofed. 



In South Africa roofs are seldom, indeed in the majority of cases 

 never, called upon to bear heavy snow loads. Further, corrugated 

 galvanised iron is in general use as a roof- covering, and this covering is 

 much lighter than the slates or tiles commonly employed in Europe. 

 For these two reasons roofs in South Africa do not require to be so strong 

 as those in Europe. It should, however, be remembered that roofs with 

 less than a certain slope may fail to shed hail as it falls. This concerns 

 not only the strength of the roof, but also its freedom, or otherwise, from 

 leakage. 



Principals of roofs in South Africa, unless of exceptional span, are 

 commonly constructed of planks 1£ inches thick, simply nailed or bolted 

 together. This does away with the necessity for the elaborate mortise 

 joints found in the stronger European roofs built of timbers of heavy 

 cross-section ; hence " plank-roofs " are eminently suitable for farm 

 buildings where skill to construct the above-mentioned mortise joints 

 may be lacking. 



These plank principals are spaced about 5 feet apart, and carry 

 2" by 3" timbers called purlins to which the roof-covering of corrugated 

 galvanised iron is nailed. The purlins run parallel to the length of the 

 building. 



Pitch of Roofs. — The term " pitch " applied to a roof means the 



