Cast in situ concrete is appropriate for all types of basement construction. It is a common form of basement construction for residential use, due to its relatively simple application, adaptability and cost. In-situ concrete is often the only appropriate form of construction for retrofit basements under existing properties, due to its relative ease of placement on site.
As with masonry, in-situ walls are most commonly installed as reinforced structures but can be used ‘plain’ (without reinforcement) following guidance provided in the TBIC Guidance Document.
Typically, cast in situ walls are constructed with steel reinforcement bars to control cracking in the structure, with particular attention given to reinforcement of the corner junctions. Plain concrete walls are not generally specified as Type B construction due to the more critical need to control crack dimensions. Workmanship is a key issue for successful implementation of Type B protection.
Water stops are included in the construction joints and particular attention is required with regards to day-working joints and the constituents of the concrete mix. Cast in situ concrete requires time to dry out before water sensitive finishes can be applied.
At basement level, floors are typically in-situ concrete. The choice of system will be driven in part by coordination with the wall construction. Floors at ground floor level in housing can be constructed using a variety of different concrete construction techniques, including in-situ, block and beam, hollowcore precast units or hybrid systems.
Typically, it is possible and beneficial to span the full width of the basement space with the floor structure. Concrete easily exceeds the minimum building regulations requirements for fire and imposed loads and provides excellent sound insulation between the spaces.
Please refer to Part A (Structure - Walls and foundations) of our building regulations guide for further information. All information correct as of 2013 amendments.
Pouring of in-situ concrete