368 FOREST PRODUCTS 



of structures and buildings, as a result of the great annual loss of life 

 and property and the decreased insurance rates offered in conformance 

 with fire underwriters' specifications have greatly stimulated the intro- 

 duction and use of these substitute materials. The best indication of 

 this condition is found in the statistics showing annual consumption of 

 wooden shingles. It has remained about stationary in the past four 

 years, whereas the demands for roofing materials of all kinds have been 

 increasing from year to year. 



Very little has been done until recently in the way of concerted effort 

 to meet this competition. Efficient and widespread advertising, more 

 careful methods of manufacture and the adoption of and adherence to 

 stricter standards should be of material assistance in maintaining the 

 demands for the wooden shingle. 



Most of the substitutes are much more expensive and in addition 

 require heavier construction in the building because of their additional 

 weight. Moreover, wooden shingles, particularly cedar, cypress and 

 redwood, are more durable as a rule than the other materials. 



Probably the most effective means of combating this question is the 

 fireproofmg of the wooden shingle. Many experiments have been car- 

 ried out .with this purpose in view; but no method has been generally 

 adopted as yet in the commercial field. The U. S. Forest Products 

 Laboratory has developed experimentally a method which may prove 

 to be commercially practicable. Air-dried shingles are subjected to a 

 treatment with a solution of borax in water. The shingles are kiln dried 

 to a moisture content of 10 per cent and then treated with a solution of 

 zinc chloride and dried. It has been determined that shingles subjected 

 to this treatment still retain their fire-resistant qualities after soaking 

 them in running water for two weeks. 



Wooden shingles have the following distinct advantages : They are 

 durable, relatively cheap, light in weight and therefore require only light 

 support ; they do not rust or corrode ; wood is an excellent non-conductor 

 of heat; they are not affected by the wind if laid and nailed properly; 

 they present a pleasing appearance and are easily laid. 



DURABILITY AND PREVENTION OF DECAY 



The value of any shingle wood depends very largely upon its durabil- 

 ity. The durability in turn of shingles is dependent upon a number 

 of factors, the chief of which are the species of wood, climate in which 

 they. are in service, pitch of the roof, size of the face of the shingles 



