Sometimes porch floors give trouble from “dusting” and wearing away of the surface to a gritty and rough condition. This may have been caused by allowing the floor to dry too quickly or by having trowelled it too much and drawn cement to the surface. It may be remedied by using some one of the commercial floor hardeners or by painting the floor with water-glass solution or boiled linseed-oil. Water-glass solution should be diluted with 4 to 6 parts of water and applied with a brush in as many coats as the concrete will absorb. When boiled linseed-oil is used, it should be allowed to dry between coats, and as many coats should be added as the concrete will absorb. Both of these treatments will darken the floor, but the latter will darken it the most, and appears to be more effective. _Tennis-Court_ In laying out any other platform construction of concrete, such as a tennis-court, the same principles of construction should be observed which were given above for sidewalks. However, more care should be taken with the drainage and foundation of the tennis-court. Not only should the 6-inch cinder or gravel bed be laid, but all around the outer edge of the court should be dug a trench about 18 inches wide and 3 feet deep. There should be laid at the bottom of this a drain-pipe, with open joints, sloping from the centre of one end of the court around both sides and joining together again at the middle of the other end and connected with another pipe to carry off the water of that drain-pipe to some lower level. The diameter of the drain-pipe should be about 5 inches and the slope 6 inches from its highest level to its lowest level. The upper surface of the court itself should slope across from one long side to the other with a pitch of 2 inches. The division lines of the slabs should follow as closely as possible the division lines of the tennis-court. The length of the concrete platform should be 21 feet greater at each end than the length of the court and the width 12 feet wider each side. This makes the entire concrete court 60 feet by 120 feet. [Illustration: Concrete Tennis-Court] _Concrete Driveway_ [Illustration: Concrete Runways to Garage] Such driveways may lead to the garage or up to the porch of the house. One of the cheapest types to the garage is a double runway for the wheels of the automobile. These runways should be about 4 feet 8 inches on centres and made 18 inches wide. They should be constructed in the same way that walks are built. Where a full-width concrete driveway is built, it should be made about 6 inches thick at the centre and 5 inches at the edges, sloping from the centre out. At intervals of every 25 feet expansion joints should be built as was specified for walks. _Concrete Steps_