Where the curb is not already in place, stakes should be set to grade and to aline either edge of the walk, the other being obtained by leveling over, taking care to allow an outward pitch on the surface of about 1/4 in. per ft. Straight-edged strips should be nailed to the inside of each line of stakes, with top edges level with them, to form the mold for the concrete. The ground should be leveled off about 10 in. below the finished grade of the walk, and well settled by ramming, as at d, Fig. 15. A foundation a, 5 in. thick should then be laid, of either coarse gravel, stone chips, sand, or cinders, well tamped or rolled. The concrete should have the proportions of 1 part of cement, 2 parts of sand, and 5 or 6 parts of gravel, mixed dry; then a sufficient quantity of water is added to make a stiff mortar. This concrete should be spread in a layer from 3 to 4 in. thick, as at b, and should be well tamped. Before it has set, the finishing coat c should be laid, and only as much concrete should be laid as can be covered with cement the same day, for if the concrete gets dry on top, the finishing coat will not adhere to it. The top coat should consist of equal parts of the best Portland cement and sand, or clean, finely crushed granite or flint rock, mixed dry, water being then added to give the consistency of plastic mortar. It should be applied with a trowel, to the thickness of 1 in., and be carefully smoothed and leveled flush with the tops of the guides. It is best to mark off the walk into squares, etc., by grooves 1/4 or 3/8 in. deep, so that in case it should crack, the fractures will follow the grooves and not disfigure the whole walk. In hot weather, the cement should not be allowed to dry too rapidly, but should be sprinkled occasionally. Usually a walk is ready for use in from 24 to 30 hours after completion, and the forms may then be removed.

The same general methods above described apply to cemented cellar floors.

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Fig. 15.

Cement Walks And Floors 309

Fig. 16.

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Fig. 17.