The terrace may be either at ground level, below ground level, or raised above it. The simplest type is ground level, which requires only the grading we have indicated. There is a wide choice of flooring materials to use. One may use cement, poured and levelled with a large board, but in maintaining the drainage grade or including shallow drainage paths, smooth turf may be used, in which case the preparation will be the same as for other lawn areas and various other types of bases.
The use of flagstones is made simple by applying a load of sand or gravel to the subsoil and digging the flagstones into the sand or gravel. The niches between the stones can be dug out and filled with top-soil and grass or other cover planted between them. This gives a very pleasing effect.
Hollow clay building tiles can be split and laid as units in the terrace floor, their rough edges in the soil. Another good surfacing material is "exposed aggregate," which is free from glare because of its rough finish. For this type of surface, build a form of 2 x 4's. Pour the flooring in squares, one square at a time, and level with a straight board. The material used is a mixture of cement, sharp sand and crushed rock or pebbles.
Redwood or cypress blocks may also be used for terrace floors and are very attractive, although somewhat less durable than stone or brick. You can buy the blocks cut to size and lay them directly in a bed of sand, which in turn has been laid on compacted gravel or cinder. Un-mortared brick, laid in a pattern, on 2 to 4 inches of well-tamped sand, with loose sand in the crevices for grass, makes a hardy and simple-to-construct terrace floor. The bricks may be laid flat or on end, and to keep them from spreading, drive an angle iron against the corners. Use a pattern that follows the lines of your terrace.
The Sunken Terrace Gardening
A sunken terrace is one which is below ground level. It can be very attractive, and it does give a feeling of coolness on a humid day or a hot night. The sunken terrace requires a retaining wall to prevent soil from continually eroding into it, and also to maintain the topsoil of the surrounding garden. The subsoil must be dug to a depth of about 5 or 6 inches below the level you wish to attain with the terrace itself. The use of sand or gravel as a base is of importance. The top treatment can follow your own dictates.
The Raised Terrace Gardening
The raised terrace is generally not fully raised, but starts at the house level and is raised at its outer edge. Again, a retaining wall is called for. The principle problem with the raised terrace is levelling. Once this is accomplished, and the retaining wall built, construction follows the same procedure as in any other case. Drainage is supplied either by a central drain, going into a tile line, or by underground piping through the retaining wall.
