They provide a flat surface for the membranes, which are then fully supported and much less likely to be punctured by subsequent construction activities.Įlevator pit waterproofing is always recommended regardless of soil conditions, as a precaution. Mud slabs are usually a 2' to 3' unreinforced concrete slab with a float finish. A mud slab can be utilized to facilitate the installation of vapor retarder membranes and waterproofing membranes. Where high water tables create contact with the slab on grade, it is necessary to waterproof the slab on grade to resist hydrostatic pressures. Vapor retarders should be selected in accordance with ASTM E 1745 and E 1993 and installed and inspected in accordance with ASTM E 1643. Poly sheets are usually 15 mils thick with taped seams, edges, and penetrations. Under slab vapor retarders may include polyethylene sheets, polyolefin sheets, high density bonded polyethylene, and asphalt/polyethylene composite sheets or polymer modified bitumen sheets.

Under Slab Vapor Retarders or Waterproofing Membrane In typical office environments, the concrete floor slab itself is comprised of 4' to 6' thick concrete reinforced with one layer of welded wire fabric at mid depth, unless below the water table, when hydrostatic heads may exert upward pressure, requiring stronger construction. Many adhesives used in applying floor coverings are sensitive to moisture requiring the use of a waterproof system or lengthy drying times if a poly vapor retarder is used. Descriptions and guidelines are provided in the following sections:ĭepending on the interior space the finish floor covering may be the exposed concrete surface itself or various floor coverings such as wood, vinyl floors or carpet. This section provides specific description of materials and systems common in floor slab systems.

The recommendation is to raise the quality of approach one degree more than the existing condition reports suggest, that is, use the higher quality material and detail it with additional reinforcements and belt and suspenders precautions applied at each level of risk perceived. Approach critical areas that will later be buried in construction with extreme conservatism. Issues of controlling soil gas emissions such as radon may also be of importance.īecause the cost penalty to correct a foundation or slab on grade waterproofing failure is either extraordinarily expensive (up to 7 times the initial cost of waterproofing) or practically impossible to correct at all after construction is complete, it is better to err on the side of caution on the initial installation. Floor slabs are often the source of leakage into the building with slab cracking of common concrete materials being a primary cause. The base floor may also be comprised of a mud or structural foundation slab complete with waterproofing and wearing slab with the overall system designed to carry structural hydrostatic pressure loads and maintain a controlled environment. The base floor within a building may simply be a cast-in-place concrete slab-on-grade with limited design considerations for structural support or environmental control functions.

Industrial grade floor grids