HEAVY TIMBER MILL CONSTRUCTION BUILDINGS 



concrete. A %-incli layer of sand and cement grout is spread 

 on top of the concrete and smoothed preferably with a tem- 

 plate until level to serve as a bed or cushion for the blocks. 



Wood blocks may be used for upper floors if desired by 

 placing under them two layers of paper laid in pitch, bedding 

 the blocks in hot pitch and filling the joints with the same 

 material. 



A good basement or shop floor is made by laying a wood 

 wearing surface on a base consisting of concrete and coal tar 

 which contains from 20 to 25 percent of creosote oil. Such 

 a floor is made by first spreading a 4-inch layer of screened 

 gravel or stone not larger than 2^ inches mixed with tar. 

 The tar is heated to 200 F., and enough used so that the mix- 

 ture will be compact when rolled. The sand and gravel should 

 be well heated before the tar is added. Often a 4 to 6-inch 

 base of Portland cement concrete takes the place of the tar 

 concrete. When cement concrete is used, it should be given a 

 coat of tar before the top course is laid. A layer of tar and 

 sand mixed in the proportion of fifty or sixty gallons of tar to 

 each yard of sand and heated to 225 F. is spread over the base 

 to a depth of 1*4 inches, and plank 3 inches thick is laid directly 

 over this top coat while it is still warm and before it sets. The 

 plank is then tamped into place, toe-nailed together, and a top 

 or wearing floor laid on the plank. 



If it is desired, an ordinary concrete floor may be used in 

 basements. Such a floor has a base similar to that described 

 for the block floor, covered with a layer of 1:2:4 Portland 

 cement concrete 4 inches to 6 inches thick and finished with a 

 wearing coat of cement and sand. This top coat is usually 

 from 1 inch to 2 inches thick and composed of a 1 :2 mixture 

 of cement and sand. Top should be kept wet for at least ten 

 days after laying. 



Floor Loads, Allowable floor loads, working stresses to 



Working Stresses, be used in design, weights of merchandise, 



Etc. and weights of timber will be found in a 



separate section at the end of this bulletin. 



Page twenty-six 



