MILL CONSTRUCTION BUILDINGS 



011 this rough floor. A fairly smooth surface must be provided 

 before the felt is laid, and any irregularity in the floor more 

 than Vs inch deep should be filled up. Two layers of felt are 

 used, breaking joints, and mopped with a sealing compound 

 between the plies and on top of the felt. These companies 

 recommend that the felt be turned up 6 inches at the posts 

 and at the side walls. The hardwood top-floor is laid in the 

 hot compound closely following the final mopping, so that the 

 nails holding it down are tightly gripped. 



At the walls the felt is protected by a counterflashing of 

 galvanized iron, or by a base-board nailed in place with the 

 joints between it and the floor covered by a quarter-round. 

 Both the base-board and quarter-round should be kept free 

 from the top-floor to allow the latter to move without break- 

 ing the corner of the turn-up in the felt. At the columns 

 the felt may be protected by a base-board and quarter-round as 

 at the walls. 



Fig. 6 gives details of 

 floor construction and f^ hin 

 flashing at side walls, as 

 described above, and as 

 recommended by the As- i^-^^S^ ^^-Toprioor 



- "i"i . - /r i r^- ,*^' A - g=g ^.v ^y*^?-^. ^ ^H -~~~~^. ^ -I!^- 



sociated Factory Mutual 

 Fire Insurance C o m- 



DanieS rioorPlank-^ Under Floor 



rnl p n Fig. 6. Details of Floor Construction. 



Ihe following extracts 



from the Building Code Recommended by the National Board 

 of Fire Underwriters are of interest in connection with the 

 general design of floor timbers and floors : 



"Wooden girders or floor timbers shall be suitable for the load carried, 

 but in no case less than 6 in. either dimension, and shall rest on iron plates 

 on wall ledges and where entering walls shall be self-releasing. Walls may 

 be corbeled out to support floor timbers where necessary. The corbeling 

 shall not exceed 2 in. 



"So far as possible, girders or floor timbers shall be single stick. 



"Where wooden beams enter walls on opposite sides, there shall be at 

 least 12 in. of masonry between ends of beams, and in no case shall they 

 enter more than one-quarter the thickness of the wall. 



"Width of floor bays shall be between 6 and 1 1 ft. 



"The practice in mill-construction of supporting the ends of beams on 

 girders by means of metal stirrups or bracket hangers is objectionable. 

 Experience has shown that such metal supports are likely to lose their 

 strength when attacked by fire and so cause collapse. 



Page twenty-three 



