284 FLOORS 



Tar Concrete Floors. The following specifications for tar con- 

 crete floors are given in circulars Nos. 54 and 55 of the Boston Man- 

 ufacturer's Mutual Fire Insurance Co., and are reprinted in Engineer- 

 ing News, March 21, 1895. 



"The floor to be 6 inches thick, and to be put down as follows : The 

 tower 5 inches to be of clean coarse gravel or broken stone, with sufficient 

 fine gravel to nearly fill the voids, thoroughly coated with coal-tar and 

 well rammed into place. On this place a layer I inch thick of clean, 

 fine gravel and sand heated and thoroughly coated with a mixture of 

 coal-tar and coal-tar pitch in the proportions of I part of pitch and 2 

 parts of tar. This layer is to be rolled with a heavy roller and brought 

 to a true and level surface ready to receive the floor plank. No sand or 

 gravel to be used while wet. 



"A floor of the kind above specified should always be protected by 

 a floor of wood over it, and the plank should be laid and bedded in the 

 top surface while it is warm and before it becomes hard. 



"For light work the thickness of the lower layer of concrete may be 

 reduced one or more inches if upon a dry gravelly or sandy soil. For 

 storage purposes where the articles stored are light and trucks are 

 little used, the following specification has been found to give a satis- 

 factory floor: 



"The lower layer being mixed and put down as above specified, the 

 top layer will be of fine gravel and sand, heated and thoroughly mixed 

 with a mixture of equal parts of coal-tar, coal-tar pitch and paving 

 cement, so that each particle of sand and gravel is completely coated 

 with the mixture, using not less than one gallon of the mix- 

 ture to each cubic foot of sand and gravel. This layer should be well 

 rolled with a heavy roller and allowed to harden several days before be- 

 ing used." 



Brick Floors. Brick floors are recommended as the most satis- 

 factory floors for round houses. Round house floors on the Boston & 

 Maine R. R. are made as follows : *Brick is laid flat on a 2-inch layer of 

 bedding sand on well compacted earth, gravel or cinders. Joints are left 

 open ^ of an inch and are swept full of cement grout. 



Round house floors are made on the Chicago, Milwaukee & St. Paul 

 R. R., as follows : *Vitrified brick is laid on edge on a layer of sand I 



*Eighth Annual Report of the Association of Railway Superintendents of 

 Bridges and Buildings. 



