Taking Concrete Steps
By Rob Gaimster
There are many concrete solutions for residential construction being used in Canterbury. These include masonry blocks, precast panels and Insulated Concrete Formwork (ICF), in which hollow reinforced polystyrene blocks are filled with concrete and plastered to provide a structural wall system.
It is however, the humble slab that is the most widely used concrete solution for residential construction.
The attraction of the concrete slab extends beyond value for money and durability. The role its mass plays in a passive solar design is also appreciated. By using concrete’s mass with the sun’s heat along with natural ventilation, more comfortable living conditions can be achieved with reduced reliance on space heating or cooling.
An exposed, insulated concrete floor absorbs, stores and later radiates the sun’s heat, off-setting temperature peaks and troughs, to create a moderate living environment.
There are proprietary slab systems available. Offering a stiffer and stronger final product than a conventional 100mm slab, the “waffle” or “raft” design creates a concrete grid between voids, typically polystyrene blocks. These slabs “float” on the ground, assisting their seismic performance. Concrete slab systems for TC3 land are also available.
Several changes to the New Zealand Building Code have been made since the Canterbury earthquakes that strengthen concrete slab’s position. Specifically, all concrete floor slabs for timber framed buildings constructed on ‘good ground’ must contain seismic grade reinforcing mesh, and perimeter foundations must be tied to the slab.
These updated regulations, combined with the benefits outlined above, along with fire resistance, sound control, and a huge range of attractive finishes, will see residential property owners across Canterbury well served by concrete slabs.
Office buildings are becoming the main feature of the central city’s construction landscape.
The areas west of the Avon in the central city, and Victoria Street, Lincoln Road or Moorhouse Avenue have seen the most activity.
As awareness of the ground conditions across the city has become more sophisticated, the use of concrete in robustly engineered foundation designs will ensure commercial buildings rest on a firm footing.
Damage resistant design solutions that use reinforced concrete, such as PREcast Seismic Structural System (PRESSS) and base isolation, will gain uptake among building designers as knowledge grows.
The next concrete step
With residential construction continuing apace, along with commercial and civil projects being completed and coming on stream, the design versatility and inherent properties of concrete will play a major part in ensuring the Canterbury built environment is attractive, robust and safe.
Rob Gaimster is the chief executive of the Cement & Concrete Association of New Zealand (CCANZ)