HEAVY TIMBER 



the girders will give added security. It is advisable to allow 

 end play in girders to prevent strains in the walls. Ends of 

 girders should be cut at an angle such that in case of damage 

 by fire, the member may tip out of the wall opening without 

 disturbing the wall. At columns, girders are supported by 

 steel or iron caps. 



Use of Inter- Where intermediate beams are used to sup- 

 mediate Beams port a floor in semi-mill construction, it is 

 preferable that the beams should rest on the 

 top of the girders direct. The width of the main girder is 

 usually sufficient to give ample bearing for the ends of the 

 beams in the bays on each side of the girder, even when the 

 ends butt together. Common practice is to suspend interme- 

 diate beams between the main girders by the use of steel or 

 iron stirrups or hangers. This practice undoubtedly lowers 

 the cost of the side walls of the building owing to the diminished 

 height of wall needed at each floor. This type of construction 

 is not looked upon with favor by insurance underwriters. They 

 claim that experience has shown that such stirrups or hangers 

 are likely to prove hazardous during exposure to fire, either 

 causing the heavy timbers to burn off quicker at the point of 

 suspension in the stirrup or hanger, or allowing the beams to 

 fall due to the failure of the metal stirrup or hanger itself. 



The Crosby-Fiske Hand Book of Fire Protection contains 

 the following comment upon this point : 



"Mill construction particularly in the Middle West, has suffered un- 

 fairly in reputation by reason of disastrous fire results, because buildings 

 somewhat resembling this type have borne its name. They may have had 

 floors and roofs of plank or wide spaced timbers, but in other particulars 

 violated the principles of 'mill construction.' A common defect has been 

 the use of exposed steel or iron stirrups to hold important floor timbers/' 



Floors Floors may be of dressed and matched or splined 

 plank 3 inches (nominal) or more in thickness nailed 

 direct to the girders. This type of floor is often called a "mill 

 floor." If heavy loads are to be carried on long spans, planks 

 6 inches or 8 inches wide are set on edge close together, firmly 

 nailed at each end and at about 18-inch intervals with 60 D. 

 nails, alternating top and bottom, thus forming a "laminated 

 floor." Each of these floors is covered with two or more thick- 

 nesses of waterproof paper or similar material and then by a 

 top, or wearing floor laid at right angles to the direction of the 



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