The use of precast panel systems for the walls of a concrete home offers the homebuyer the opportunity to control the quality of the end product to a very high degree, as precast panels are usually supplied from specialist precasting factories. Casting multiple panels from the same mould can also help reduce building costs.
A variety of attractive surface finishes are possible using precast panels, some of which eliminate the need for any ongoing coatings or other decorative finishes. Savings in construction costs are also possible if the surfaces of the precast panels can be left unpainted or unlined. Precast construction is often chosen by designers and/or builders seeking to achieve a particular look as it provides limitless flexibility of shape and size. Consideration given to the placement and treatment of panel joints can also reduce costs.
Precasting offside can also improve the speed of construction. While the panels are being prepared, workers can spend time preparing the site. Once the floor slab or foundation is made ready to accept the system and the panels are delivered, it is often possible to erect all of the walls within a day, and have the house closed in and secured shortly thereafter.
Another option is to precast the panels on site (variously referred to as 'site precasting' or 'tilt-up construction'). Tilt up panels will save money on transportation costs to site, particularly if the site is remote. They are also an option when there is little room for cranage on the site. The panels can be cast in position and once cured, erected with the use of a lifting frame. The size of the precast panels is limited by the area of flat surface on which to cast and by the lifting equipment.
The quality of on-site precast panels is dependent on the experience of the on-site personnel and on the site conditions. Absolute and expert control of the preparation, casting and curing of panels, and the creation of particular special surface finishes, may only be possible from a dedicated precasting factory.
Precast panel systems can be manufactured with higher insulation values by the use of various insulating mediums. Most common is the use of polystyrene sheeting attached to either the interior or exterior face of the panel. The polystyrene can also be located within the panel (referred to as 'sandwich panel construction'). Insulating plaster renders can also be applied to the panel surface. Another option is to strap and line from the inside, with insulation (usually a fibre system such as glass or wool) in the cavity.
As with some forms of masonry construction, panels insulated on the internal face of the wall isolate the mass of the wall from internally reflected and radiated heat. This can reduce some of the benefits of the high mass system. One system involves casting the concrete panel onto a layer of polystyrene with splayed ribs. These ribs help the concrete key to the insulation. These walls can then be clad using conventional wallboard systems.
Panels insulated on the external face of the wall only will provide thermal mass to the interior, and require an external plaster coating to protect the insulation from possible damage. Precast systems with insulation in the middle of the panels mean that the thermal mass is available to contribute to the comfortable living environment in the home and the exterior is a robust concrete surface. Some manufacturers produce these panels to a regular modular size, using window and door openings to break up the wall for architectural relief, while others cast panels to a range of sizes and shapes.
Precast panels can also be constructed of lightweight concrete. These panels are usually reinforced with fibres rather than conventional steel reinforcing and can have a variety of finishes applied or cast integrally on the surface. One system uses a material that is only 33% of the weight of conventional concrete. Services can be run easily through the void formed by the permanent steel frames on the inside face of the panel, which can then be lined with traditional materials. Lighter panels mean that smaller cranes can be used to lift and place the panels with consequential cost savings. Using lightweight panels is a good option when building on softy unsteady soil and could also result in lower costs for the foundations due to the lower mass of the panels. These panels have a higher insulation value but lower thermal mass capacity than conventional concrete panels.