Concrete is the most common and appropriate material used in the construction of new basement walls and floors. This is due in part to cost and availability but also its inherent resistance to water, durability under ground and ability to provide a stable structural surface for the support of waterproofing membranes.
The method of construction chosen will depend upon consideration of various factors including: potential repetition of construction elements; accessibility for labour and cranes; cost; and fundamentally, the type of construction system permitted according to water table and use. Most forms of concrete construction can provide a variety of wall thicknesses to suit the particular structural requirement of each basement.
For more information on concrete construction methods, see pages on:
Concrete is inherently water-resistant and robust, making it suitable for subterranean construction. Its water resistance can be further enhanced by the introduction of admixtures. These admixtures (hydrophobic and pore blocking) act to reverse the capillary or ‘sucking’’ action of the tiny capillaries on the concrete surface and to effectively block the pores within the concrete when subjected to hydrostatic pressure. The result is a dry concrete that protects from water ingress. Such proprietary concrete mixes are available for this purpose from a number of specialist suppliers. Warranties can be obtained for products and workmanship on site.
It is still possible for small levels of water vapour to pass through these types of concrete but they are generally very low and so unlikely to cause a problem. Additional membranes or ventilation may be considered, depending upon site conditions, proposed use and client or designers’ assessment of, and attitude to, risk.