MechChem Africa

MechChem Africa columnist Gary i Crawford of Crawford Consulting gets to grips with the realities of his light steel frame (LSF) house project in Hartbeespoort and highlights key differences between LSF and building using traditional materials.

Four years from the design of House Crawford by Sharon Lane Crawford; the Light Steel Frame (LSF) design and detailing by Nardi van Zijl; and the foundation and structural engineering design by Mike Stoop of Andy Kolver Civil & Structural Engineers, the plans for this novel home are now approved and construction has begun.

House Crawford Gary LSF

While expecting lengthy delays in having the plans approved by the Gateway Manor Home Owners Association, the Madibeng Local Municipality and the National Home Builders Registration Council (NHBRC) – we took the opportunity to build the boundary wall. At the required height of 1.8 m, the plus 100 m wall incorporates a 12.0 m section of un- climbable and highly tamper resistant ‘ClearVu Invisible Wall’ panels to take advantage of the view of indigenous trees and mountains.

Amazingly, the building plans were approved in a matter of days, courtesy the Estate Architect, Gavin Wreford, and the efficient staff of the Madibeng Building Control Division. Cooperation and friendliness seem to be the norm in Hartbeespoort.

A “Hi Gary,” greets me as I enter Basil’s supermarket or the local hardware store; on visiting Vovo Telo restaurant for the third time, we’re offered our ‘usual’ table by owner John; and the ladies at non-card-accepting ‘home-cooked’ gourmet meals shop, Mr Salad, extend me ‘docket on a spike’ credit when I pitch up cashless. We even get to jump the queue at funky eatery, French toast, where our Afghan hounds have become the Sunday centre of attraction.

We moved to Hartbeespoort (I’ve yet to call it ‘Harties’) to be closer to the building site of our ‘off-the-grid’ LSF residence. We received, as a bonus, instant acceptance and friendliness.

LSF: the underpinning rationale

The starting point for this project was to de- sign a home that would incorporate the latest in environmental practices. In researching the appropriate materials, carbon footprint, longevity, economics, ease of construction and appearance, the Light Steel Frame (LSF) system emerged as the clear favourite.

The home had to accommodate the needs of two mature (yet active) adults, two Afghan hounds and a regular flow of visitors. The building had to be low maintenance and incorporate features conducive to environ- mental stability. The two identical bedrooms had to have direct access to the open plan living space.

An internal ‘eco garden’ will control airflow, while leading off the garden will be two studios flanking an entrance hall.

A characteristic of the building design is the use of polycarbonate sheeting supplied by PALRAM. The cladding of some walls will see the conventional drywall cladding replaced by SUNLITE multi wall PLC sheet in an opal colour – this to provide a theatrical ‘glow-at-night’ feel.

The same material is specified on interior doors, all of which will be ‘sliders’ rather than conventional hinged doors. The doors will be suspended on ‘barn door’ sliding mechanisms of our own design. Because of the artistic quality of the mechanisms, they’ll be left exposed. At the time of writing this column, the foundation layout is to commence. A detailed examination of soil conditions has been completed and various types of foundation from ‘raft’ to steel piles were considered. In end, we decided to use a ‘strip’ foundation and slab.

With a slab/screed of 100 mm thick, the floor will extend to the exterior wall brickwork. Since this is the surface on which the house structure will stand and it will be power floated.

The case for under-floor insulation

Besides the usual moisture barrier and mild steel reinforcing mesh, hindsight advocated the use of 40 mm high-density (20 kg/m3) expanded polystyrene (EPS) as under-floor insulation. It has been proved that … read more.

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