WOODEN FLOORS 287 



three courses. The stones in the lower course were to be not less than 

 I inch in diameter. Stones in each course were well covered with tar 

 before laying and were well tamped and rolled afterwards. The third 

 and finishing course was composed of good clean sharp sand well dried, 

 heated hot and mixed with pitch and tar in proper proportions. This 

 was then carefully rolled and brought to a true level to fit a straight 

 edge. On the finished surface of the foundation was spread a coating 

 ^-inch thick of best roofing pitch put on hot and into which the lower 

 course of the plank was laid before the pitch cooled. 



Care was taken to have the planks thoroughly bedded in the pitch 

 and after laying, the joints were filled with pitch. If vacant spaces 

 appeared under the plank, they were filled up with pitch by boring 

 through the plank. The cost of this flooring was about 1 8 cents per 

 square foot, using spruce lumber. 



A cheap but serviceable floor may be made as shown in Fig. 136. 

 The soil is excavated to a depth of 12 to 15 inches and cinders are filled 

 in and carefully tamped. The flooring planks are nailed to the sills 

 which are bedded in the cinders. The life of the plank flooring can be 

 increased by putting a coating of slaked lime on top of the cinders. 





FIG. 136. 



The floor shown in Fig. 137 was used in the factory of the Atlas 

 Tack Company, Fairhaven, Mass., and needs no explanation. 



,--/ 



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 Transverse 



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FIG. 137. 



