Floors should be estimated for according to the nature of the building and the probable load. A crowd of persons is variously estimated to weigh from 411b. to 147'41b. per square foot of the surface covered. Probably a safe average would be 1 cwt. per ft. super, considered as a live load. Dwelling houses are usually designed for a dead load of l 1/4cwt. per foot super., churches and public buildings 1 1/2 cwt., and warehouses 2 1/2 cwt. The weight of the structure must be allowed for in addition to the above loads, and this is most important to bear in mind in connection with fireproof floors.