This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Floors in manufacturing buildings are often finished with a 1-inch coat of cement and sand, which is usually mixed in the proportions of 1 part cement to 1 part sand, or 1 part cement to 2 parts sand. This finishing coat must be put on before the concrete base sets, or it will break up and shell off, unless it is made very thick, 1 1/2 to 2 inches. A more satisfactory method of finishing such floors is to put 2 inches of cinder concrete on the concrete base, and then put the finishing coat on the cinder concrete. The finish coat and cinder concrete bond together, making a thickness of three inches. The cinder concrete may consist of a mixture of 1 part cement, 2 parts sand, and 6 parts cinders, and may be put down at any time; that is, this method of finishing a floor can be used as satisfactorily on an old concrete floor as on one just constructed.
In office buildings, and generally in factory buildings, a wooden floor is laid over the concrete. Wooden stringers are first laid on the concrete, about 1 1/2 to 2 feet apart. The stringers are 2 inches thick and 3 inches wide on top, with sloping edges. The space between the stringers is filled with cinder concrete, as shown in Fig. 121, usually mixed 1:4:8. When the concrete has set, the flooring is nailed to the stringers.
Fig. 121. Cinder Pill between Stringers.