ESTIMATE OF COST 349 



per cent to the weight of the framework exclusive of the purlins and 

 girts where end bent (b) Fig. i, is used. In the estimate given it will 

 be seen that the per cent is only 22, the small value being due in part 

 to the use of channel eave struts and the end post framing. 



In estimating the weight of corrugated steel add 25 per cent for 

 laps where two corrugations side lap and 6 inches end lap are required, 

 and 15 per cent where one corrugation side lap and 4 inches end lap are 

 required. 



The weights of the sections, rods, bolts, turnbuckles, etc., are ob- 

 tained from Cambria Steel, or other handbook. 



The engineer should use every care to check his work in making 

 estimates, the material should be checked off the drawings, and the cal- 

 culations should be carefully checked and rechecked. Slide rules and 

 adding machines are invaluable in this work. No results should, how- 

 ever, be allowed to pass until they have been roughly checked by the 

 engineer by aliquot parts, or by making a mental estimate of each 

 quantity. The engineer can soon develop a sense of estimate, so to 

 speak, and will often detect blunders intuitively. Accuracy is of more 

 value in estimating than precision. While the method outlined may 

 seem somewhat crude at first glance, it is nevertheless true that a pre- 

 liminary estimate made by a skilled man will commonly be within I or 2 

 per cent of the shipping weight, and if off more than 2^ per cent it is 

 pretty certain that there was something wrong either with the estimate 

 or with the estimater. The estimated weight should be a little heavy 

 rather than light, say I to 2 per cent. 



ESTIMATE OF COST. The cost of the different parts of a 

 mill building varies with the local conditions, cost of labor, and cost 

 of materials. The discussion of this subject will be divided into (i) 

 cost of material, (2) cost of shop work, and (3) cost of erection. The 

 cost of transportation must also be included in arriving at the total cost. 

 The subject of costs is a very difficult one to handle and the author 

 would caution the reader to use the data given on the following pages 

 with care, for the reason that costs are always relative and what may 



