ONE HUNDRED THOUSAND FACTS FOR THE PEOPLE. 421 



by which means it dries sooner and is less 

 liable to rot. The slips put between the 

 halves or flitches should be thick enough 

 to allow the air to circulate freely between 

 them. 



Ceiling Joists. — If 2 inches be fixed 

 upon for the thickness of ceiling joists, 

 the rule for finding the depth becomes 

 very easy; for half the length in ieet 

 gives the depth in inches — that is, if the 

 length be 10 feet, the depth should be 5 

 inches; if 12 feet, the depth will be 6 

 inches, and so on for any other length. 



Wall plates should be made stronger 

 as the span becomes longer. 



The following proportions may serve 

 for general purposes : 

 For a 20 feet bearing 4^ by 3 inches. 



* 30 " 6 by 4 " 



" 40 " 7K b 7 5 " 



Construction of Roofs. — The height of 

 roofs is seldom above one-third of the 

 span, and should never be less than one- 

 sixth, except for metal or composition. 



The usual pitch is that when the height 

 is one-fourth of the span, or at an angle 

 of 26^ degrees with the horizon, this 

 inclination is adapted to the covering 

 with slates or shingles. 



For roofs whose spans are between 20 

 and 50 feet, no more than a truss with a 

 king-post and struts will be necessary, in 

 which case the scantlings here-under 

 given will be sufficient, viz. : 



In. In. 

 For a span of 20 feet, the beams 



to be - - - - 9 by 4 

 The king-posts, - - r 4 by 4 

 Principal rafters, - - - 4 by 4 



Struts, 4 by 3 



For a span of 25 feet, the tie 



beams, - - - - 10 by 5 

 The king-posts, - - - 5 by 5 



Principal rafters, - - - 5 by 4 

 Struts, - - - - "5 by 3 

 For a span of 30 feet, the tie 



beams, - - - -n by 6 

 The king-posts, - - - 6 by 6 

 Principal rafters, - - - 6 by 4 

 Struts, - - - - - 6 by 3 



For roofs whose spans are between 30 

 and 33 feet, a truss with two queen-posts 

 and struts will be required, and a straining 

 piece between the queen-posts. Thus : 



For a span of 35 feet, the tie beams to 

 be 1 1 inches by 5 inches ; queen-posts, 4 

 inches by 4 inches; principals, 5 inches 



by 4 inches ; straining piece, 7 inches by 



4 inches; struts, 4 inches by 2 inches. 

 For a span of 40 feet, the tie beams to 



be 12 inches by 5 inches; queen-posts, 5 

 inches by 5 inches; principals, 5 inches 

 by 5 inches ; straining piece, 7 inches by 



5 inches; struts, 5 inches by 2)4 inches. 

 For a span of 45 feet, the tie beams to 



be 13 inches by 6 inches; queen-posts, 6 

 inches by 6 inches; principals, 6 inches 

 by 5 inches ; straining piece, 7 inches by 



6 inches ; struts, 5 inches by 3 inches. 

 For roofs whose spans are between 45 



and 60 feet, two sets of queen-posts are 

 required, and a straining piece between 

 them; struts from the larger to the smaller 

 queen-posts, and struts again from the 

 latter. 



For a span of 50 feet, tie beams, 13 

 inches by 8 inches ; queen-posts, 8 inches 

 by 8 inches ; small queens, 8 inches by 4 

 inches ; principals, 8 inches by 6 inches ; 

 straining piece, 9 inches by 6 inches; 

 struts, 5 inches by 3 inches. 



For a span of 55 feet, tie beams, 14 

 inches by 9 inches ; queen-posts, 9 inches 

 by 8 inches ; small queens, 9 inches by 4 

 inches ; principals, 8 inches by 7 inches ; 

 straining piece, 10 inches by 6 inches ; 

 struts, $)4 inches by 3 inches. 



For a span of 60 feet, tie beams, 15 

 inches by 10 inches; queen-posts, 10 

 inches by 8 inches; small queens, 10 

 inches by 4 inches; principals, 8 inches 

 by 8 inches; straining piece, n inches 

 by 6 inches; struts, 6 inches by 3 inches. 



The scantlings of purlins are regulated 

 principally by their bearing, which ought 

 not to exceed 10 feet. 

 For a bearing of 6 ft., the scant- 

 ling should be - - - 6 by 4 

 For a bearing of 8 ft., the scant- 

 ling should be - - 7 by 5 

 For a bearing of 10 ft, the scant- 

 ling should be - - - 8 by 6 



For common rafters the scantlings are 

 as follows : 



12 feet should be the maximum ot 

 bearing. 



For a bearing of 8 ft., the scant- 

 ling should be - - 4 by 2 

 For a bearing of 10 ft., the scant- 

 ling should be - - - 5 by 2 

 For a bearing of 12 ft., the scant- 

 ling should be - - 6 by 2 



In measuring carpenters' work it would 

 be impossible to specify all the methods 



