HEAVY TIMBER 



Size of The width of floor and roof bays will vary from 8 to 

 Bays 11 feet on centers where the planks of the main floor 

 are laid flat and no intermediate beams used. If the 

 planks are set on edge, the bays will commonly vary from 12 

 to 18 feet in width, depending in any case upon the general 

 design of the building, the amount of floor load, and an econom- 

 ical arrangement of the pipes for the sprinkler system. Econ- 

 omy in the use of lumber is effected by making the span such 

 that the full working strength of a given commercial size of 

 material may be utilized, and the material used in standard 

 lengths. Excessive deflections must be guarded against in 

 any design. 



The length of bays may be as great as 20 to 25 feet, but 

 16 feet is more common in ordinary buildings. Again, the 

 design of the building and the sizes of material easily obtained 

 determine this dimension. 



Crosby and Fiske in their "Hand Book of Fire Protection" 

 refer to the width of bays as follows: 



"Narrow bay construction (4 feet to 5 feet center to center of timbers) 

 is not true mill construction and is undesirable for several reasons. There 

 are more corners, angles and surfaces on which fire may feed and spread. 

 Water from sprinklers or hose streams cannot be used as advantageously. 

 Owing to the expense, and also because of the greater number of sprinklers 

 in the same fire area, it is not always feasible to place a line of sprinklers 

 in every bay, and if this latter is not done the sprinkler protection is not 

 as satisfactory. Less than 6 foot bays are not advised, and if used the 

 building should not be classed as of 'mill' construction." 



Height of The height of different stories of a building may 

 Stories be controlled by the character of occupancy or by 



special processes necessary in the manufacturing 

 industries. Where no special features are to be provided for, 

 the heights shown in Table II may be used as a guide: 



Table II. Height of Stories from Floor to Floor. 



Width of Building Height of Stories 



25 feet 12 feet 



50 feet 13 feet 



75 feet 14 feet 



100 feet 15 feet 



125 feet 15 feet 



The National Board of Fire Underwriters recommend that 

 no story of any building above the first story shall exceed 

 15 feet in height. 



Page sixteen 



