HEAVY TIMBER 



that expansion in the floor due to dampness will not cause 

 movement in the girders at the walls. 



The top-floor may be of softwood or hardwood as use 

 demands. Tongued and grooved flooring is used almost en- 

 tirely. Square-edged flooring is easier to replace when repairs 

 are needed, but wears less around nails, thus making an un- 

 even floor. Some of the best buildings have a double top-floor, 

 the lower part of softwood laid diagonally upon the plank 

 under-floor, and the hardwood upper part laid lengthwise. 

 This latter method allows boards in alleys or passages to be 

 easily replaced when worn, and the diagonal boards brace the 

 floors, reduce vibration, and distribute the floor load evenly. 

 The top-floor should always be laid so that the length of the 

 pieces is parallel to the direction of the traffic or trucking. 

 Usually this is lengthwise of the building. 



7 Bronze 

 Clapper 



Top Floor 

 2-P/yFelt 

 " Under 

 Floor: 



Horizontal Section Vertical Section 



Fig. 5. Scupper for Drainage of Floors. 



If extra precaution is desired to prevent leakage of water 

 through floors, the various layers of waterproof paper should 

 be laid to break joints and each joint mopped with hot tar or 

 a similar protective material. Also, floors may be given a 

 pitch of 1 inch in 20 feet, and scuppers similar to that shown 

 in Fig. 5 installed at floor level. These are ordinarily spaced 

 from 20 to 40 feet apart along the wall. 



The Associated Factory Mutual Fire Insurance Companies 

 recommend the use of an approved elastic felt instead of 

 waterproof paper. Their experience has been that felt prop- 

 erly laid gives better satisfaction in the long run. These com- 

 panies recommend that a rough board floor be laid on top of 

 the heavy plank floor, and that the waterproof felt be placed 



Page twenty-two 



