I'm not sure that I'd ever given much thought to the Railroads needing or using sand before but below is some basic information on a Sand house build for and maintained in Richmond VA. from "Buildings and Structures of American Railroads."
Sand-house at Richmond, Va., Richmond & Alleghany Railroad.—The sand-house of the Richmond & Alleghany Railroad, shown in Figs. 174 and 175, is a good type of a cheap sand-house, where a limited amount of sand is used.
The house is a low frame structure, 16 ft. 6 in. × 14 ft. 6 in., with an open bin, 6 ft. 6 in. X 14 ft. 6 in., adjoining one end of the building for the wet sand. In operating this house the wet sand is delivered from cars into the open bin, and from thence it is shovelled, as required, through an opening in the side of the building into an interior storage-bin for wet sand. A cast-iron sand-drying stove is located in the middle of the house, which is filled from the wet-sand bin. As the sand dries, it drops to the floor through openings in the sides of the stove, from where it is thrown on a screen placed over the dry-sand bin at the other end of the building. The enginemen are required to enter the house and fill their buckets with sand directly from the dry-sand bin.
The frame is 10 ft. high on the front of the building and 9 ft. on the rear. The principal sizes are as follows: sills, 4 in. x 6 in. ; plates, 4 in. X 4 in.; corner and door studs, 4 in. X 4 in.; intermediate studding, 3 in. X 4 in., spaced about 18 in.; nailers, 3 in. X 4 in.; rafters, 2 in. X 6 in.; posts for bin partitions, 3 in. X 4 in.; rails for bin partitions, 4 m. X 6 in.; floor in bins, 2 in. ; outside sheathing, J-in. vertical boards with battens; roof-sheathing, Jan. boards, covered with tin.
While, as stated above, this is a representative design for a cheap sand-house, it could be improved by roofing over the outer wet-sand bin, and the second handling of the wet sand from the outside bin to the interior one should be avoided.