An ever-increasing number of new houses in New Zealand are being built on concrete ground floor slabs, the result of builders and homeowners having discovered the benefits of concrete ground floor slab construction. The inherent qualities provided by concrete floors are dependent on good design and construction practices. Concrete is formed on site through a series of sequential steps. Careful control must be maintained throughout to help ensure maximum benefit from the material.
Concrete slab floors provide good resistance to the lateral transmission of impact noise, which results in a quieter home. Concrete floors also perform well under seismic loads, as the earthquake forces are distributed over a greater area of ground, thus reducing the risk of foundation movement.
When building on a flat site, a concrete slab is generally less expensive to construct than a suspended timber floor. On flat and gently sloping sites (up to 15°), the speed of construction of a slab-on-grade is also competitive with that of a timber floor.
The high thermal mass of concrete allows floors to be used as part of a passive solar heating system. Another advantage of a concrete floor is that a heat supply can be cast directly into the slab, in the form of electric cables or piped hot water. Embedded heating systems reduce the occurrence of cold air draughts at floor level and reduce the risk of humidity and mildew, without taking up any room space.
Methods of finishing a concrete floor are almost endless, ranging from steel trowelled to ground or polished finishes, to stained or pigmented concrete. Other finishes include exposed aggregates, imprinting in a variety of patterns and layouts, and a range of inlaid materials, including metal strips, timber, glass and even plastic. While there is an initial capital cost of finishing a concrete floor, a well-finished and attractive floor slab means that the cost of applied floor finishes can be avoided.
Instead of a surface treatment, the concrete slab can also be covered in a common flooring material such as linoleum or vinyl tile, or hardwood flooring. However, these types of materials reduce the effectiveness of the use of the floor mass in controlling internal temperatures. Materials such as slate, concrete or ceramic tile enable the floor mass to be fully utilized to improve thermal comfort.