With ever increasing building costs, the requirement for rapid building and greater awareness of energy conservation as an important aspect of building design, expanded polystyrene (EPS) is becoming increasingly used in modern day construction.
The National Building Regulations and Building Standards Act of 1977 has been amended to introduce legislation that calls for more energy efficient construction technologies and building methods.
The amendment, dubbed SANS 10400 – XA, took effect on 9 November 2011 and stipulates that at least 50% of yearly average hot water heating
requirements in a building must be provided by means other than electricity. Alternative energy sources are referenced as solar heating, heat pumps, heat recovery from other systems and renewable combustible fuel.
In addition, the Act will require greater insulation of building envelopes to improve of energy efficiency and ultimately reduce overall electricity
consumption.
Owing to the fact that the legislation has been under discussion for more than five years, most construction companies have accepted the inevitability of the changes.
Many architectural companies now provide specialised services in this regard and some firms will work only on energy efficient projects. We are seeing an increase in the number of clients who request energy efficient solutions, and developers that are demanding energy efficient solutions.
The slab is a combination of a moulded EPS block and pre stressed ribs to form a coffer slab system for multi storey buildings.
The system comprises a priority high strength concrete rib to support the high density Slabline void formers, which clip into a concrete ash block tray.
The system is completed by the placement of reinforcing bars between the blocks and reinforcing mesh. Concrete is poured to fill the channels, encapsulating the rebar and mesh to form the structure of the floor slab.
The void formers are left in place and act both as thermal and sound insulator solutions.
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- The floor slab is designed taking into account the span and imposed loading requirements by combining the variables of rebar size and configuration and concrete beam depth. The beam depth is controlled by the 4 different block heights.
- Support wall structures are built as normal.
- Ribs are placed uni-directionally onto the supporting walls and are propped at 1.6 meter intervals to support the wet concrete and construction loading.
- Steel reinforcing is fitted between the blocks.
- Steel reinforcing mesh is placed above the blocks.
- If needed, formwork is placed around the perimeter of the floor area and service ducts to confine the concrete pour.
- Concrete is poured to complete the slab.
- Ceilings can be either suspended or plastered.
The thermal slab system can be used in the following application areas:
- Double storey residential
- Multi storey commercial building
- Hotels
- Flats, duplexes and apartment buildings
- Shopping centres
- Suspended ground floor slabs
- Renovations
- All the components are lightweight and are easily installed without cranes, lifting equipment or excessive labour.The slab is approximately 30% lighter than an equivalent thickness concrete rib and block slab – this equates to a saving of about 150kg/m² on a 255mm slab.Compared to concrete in normal solid slabs the weight saving is even more significant – on a 255mm deep concrete ‘insitu’ slab the weight saving is close to 320kg/m².The blocks can be cut with a handsaw when full blocks do not fit and complex shapes have to be covered.Electrical and other services can also be cut into the EPS and run through the blocks themselves.During the construction phase the blocks can support workmen and equipment allowing full access to the working area without fear of breakages or damage. Similarly the system will support the concrete, provided the lintels are propped at the recommended intervals.EPS is used extensively as thermal insulating material and performs this function in the slab moderating building temperatures and reducing energy costs associated with heating and cooling. Slabline thermal insulation is 7 times better than the equivalent thickness in ‘insitu’ concrete slabs.EPS also acts as a sound barrier and in combination with the concrete mutes all sound waves that could potentially be transmitted through the floor slabs.The U value of a 255mm slab is 0.41W/m²K vs the U value of an equivalent ‘insitu’ concrete slab of 3.45W/m²K.A fire retardant grade of EPS is used to manufacture the polystyrene blocks and as a result they do not add to any existing fire hazard and will not contribute to the development phase of a fire and will not propagate flame.EPS is rot, rodent and termite proof and is dimensionally stable and will thus retain its thermal and sound insulating properties for the life of the building.Slabline is cost competitive when comparing material cost versus traditional concrete systems but, becomes increasingly competitive when the cost of labour, equipment requirements and time are taken into consideration.Fewer props are needed per m² for Slabline slabs when compared to other concrete systems. This is made possible by the use of T-beams which do not need to be propped under 4.5m.‘insitu’ Beams are to be box shuttered to accommodate the depth required .Skylights are easy to install by leaving out blocks and creating edge formers and side shuttering the areas required.
The floor slab meets the requirements of all the major codes – SABS10100, B8110, UBC and ACI and SANS10400 – XA.
