THE FLOOR slab is one of the elements in a building construction most likely to cause problems, such as cracking, deflection – or even collapse in a worse-case scenario. Therefore it’s critically important that home-owners, and building contractors too, know how to identify a genuine hollow-core precast concrete floor slab.
This advice comes from Echo Floors, the country’s largest hollow-core concrete floor panel manufacturer, following complaints it has recorded about the quality of some “do-it-yourself” flooring systems being sold as precast.
“Other than hollow-core there is no true precast slab available on the market – yet some systems are being sold as such,” says Echo Group marketing director Melinda Louw. “It is most important that home-owners know exactly what type of slab their builder is using. A number of clients who have approached Echo Floors for slabs for a new house or a building addition report having had bad experiences with what you might describe as do-it-yourself flooring systems.”
At first sight, the “DIY systems” always appear cheaper. That’s because there are a number of hidden costs, she says. “The price quoted is merely for the skeleton of a slab – beams, hollow blocks and reinforcing are off-loaded on the pavement. The builder is presented with a drawing of how to place the materials, after which the slab supplier will send an engineer to check compliance with its requirements.”
Additional costs typically include:
• Labour and supervision of the placement of the materials.
• Prop-hire, propping, formwork for stiffening ribs.
• Formwork for support beams and in-situ areas.
• Readymix concrete.
• Plastering of ceilings.
• …And a variety of additional supervision, labour, plant and materials costs.
“The suspended floor on a building is one of the most – if not the most – critical structural element,” says Ms Louw. “It is also one of the most complex elements, and one of the most difficult to construct. It’s therefore the one most likely to cause problems with the structure. This raises the question of responsibility and liability should problems occur, and that can involve several disputing parties.
“But with true hollow-core precast slabs, we – Echo Floors, with our SABS ISO 9001 accreditation and over 20 years in the industry – take sole responsibility for the entire slab.”
A forrest of gum poles used as props supported on broken bricks. A “recipe for disaster”.
A typical example of the horrendous quality of d.i.y. systems used in the building industry.