A geocomposite consists of a combination of geotextile and geogrid; or geogrid and gromembrane; or geotextile, geogrid, and geomembrane; or any one of these three materials with another material (e.g., deformed plastic sheets, steel cables, or steel anchors). This exciting area brings out the best creative efforts of the engineer, manufacturer, and contractor. The application areas are numerous and growing steadily. The major functions encompass the entire range of functions listed for geosynthetics discussed previously : separation, reinforcement, filtration, drainage, and liquid barrier.

All surfaces on which the lining is to be laid, must be prepared so that no damage to the lining is possible.
The surface shall be free of all rocks, sticks, stones, roots, sharp objects or debris of any kind. The surface should provide a firm unyielding foundation for the membrane with no sudden, sharp or abrupt change or break in gradient. No standing water or excess moisture shall be present. The surface must be constructed to allow the necessary compaction. 90% proctor with a surface tolerance of ±25mm for plastic materials, 80% proctor and ±50mm for rubber materials.

If after inspection of the surface to be laid on it is deemed unsuitable, sand blinding or an approved geotextile may be required as a protection layer.