Lightweight Steel Gets Serious
The new SA Army Foundation conference centre in Centurion has been described as one of the most complex lightweight steel frame constructions ever undertaken in this country. LAD joined lead designer and project manager of the conference centre project Werner van der Poll from BASE Architects & Associates on site to witness the final days of construction.
What was your brief on this project?
The client required a small conference facility housing 120 people as well as breakaway rooms that could convert into an open plan dining facility – the zoning on this site didn’t allow for anything bigger than this. There was also the option of creating accommodation for guests to spend the night. The existing on site building was the old Wierdabrug police station. I saw this as a great opportunity to utilise some of the old building’s classical features and incorporate them into a more modernised version. One of the aims was for this building to sit comfortably within its environment and yet stand out proudly.
Why was lightweight steel frame chosen as the building material?
We had previously built a McDonald’s building out of lightweight steel frame which raised the following question in our minds: Why are there not more commercial projects in South Africa created using lightweight steel? BASE Architects &Associates also prides itself on being at the forefront of working with new and innovative ideas and technologies brought to the South African and international markets.
The key factors that drove BASE to propose lightweight steel frame technology as an option for this client was that it was more cost effective. Also, the build time would be shorter which, I find, is always an attractive point to commercial clients especially.
Another important factor in lightweight steel frame structures is the building insulation properties versus brickwork. When done properly, this type of construction is superior when it comes to insulation, which in turn brings down heating and cooling costs dramatically. Plus it makes for a very ‘green’ building.
A lightweight steel frame also allows different disciplines to work concurrently. For example, it is not necessary to wait for a completed façade before finalizing accurate measurements for windows. Window apertures can be agreed up front with the glass and aluminium contractor, even before the lightweight steel frame walling is installed, since the system is extremely accurate. With lightweight steel frame one can work to a tolerance of 5mm.
The SA Army Foundation conference centre has been described as one of the most complex lightweight steel frame buildings ever undertaken in SA. What were the challenges and opportunities you faced during the process?
Since lightweight steel frame construction is still a relatively new way of building in South Africa, there are not a lot of references, especially when it comes to complex commercial projects. However, the challenges and surprises along the way are what make it interesting! For instance, the entrance of the conference at the gable end was connected to the rest of the structure by only a shop front as well as the in lay of the gable end – a tricky structure in any design. Using traditional construction methods, this may have been a detail that would have been cut out of the design to save costs, but with lightweight steel frame it became structurally more feasible – plus it was more budget-friendly. In addition, using different materials like sheeting and fibre cement boards on the conference centre building, which we wanted to keep on the same plane, meant we had to add extra structural skins to achieve a cleaner, more simplistic look.
There were many challenges on this job: One of these was the number of chamfered walls and angled windows; this ended up being more complex than if we had been working with bricks and mortar. The steel gets manufactured in panels that always have a thickness of 90mm. Placing the panels at an angle creates gaps in the structure that needed to be completed with other construction techniques – this was not as easy as we initially anticipated.
Did the lightweight steel frame material influence the architectural style?
The lightweight steel frame didn’t actually affect the design at all, in fact complemented the feasibility of the project. There wasn’t that much compromise on the style and design.
How does light weight steel frame construction method add to the sustainability of a project and a building?
Lightweight steel frame construction offers designers and building owners the opportunity to minimize energy wastage during building operations, as well as during the lifetime of the building.
Worldwide, the primary steel industry has recently vastly improved production processes to minimize energy consumption and pollution. Furthermore, a large percentage of all scrap generated is reused in electric arc furnaces to produce new steel, resulting in significant energy savings and a reduction in pollution.
The mass of a wall in a lightweight steel frame building is ten times lighter than that of a brick wall. Thus, significant energy savings are achieved merely in transporting the materials to the building site. In addition, material wastage on site is minimised, again reducing energy wastage by obviating the need to remove truckloads of building rubble after completing the building process.
In terms of this project, material wastage was reduced by 30%, transport costs were down by 80% and the carbon footprint of the building process was also significantly reduced.
Once the building is erected, the energy savings really take shape: The high density polystyrene spacers on the steel in the wall help with the equalizing of temperatures, giving the steel time to adapt to the fluctuation of temperature. Added to this is the glass-wool insulation in the wall cavities, plus 15mm fire resistant gypsum board on the inside – all this insulation provides a massive reduction in heat loss.
This building is a 1000% more insulated than its bricks and mortar equivalent would be, so the mechanical ventilation and energy usage in the building is significantly reduced.
There is only 2%material wastage on the building site, which means there has been a significant saving in energy.
Finally, angled windows help with maximising the use of natural light. Selecting the correct high performance glass for each area in the building has added to the reduction of energy consumption.
Would the person visiting this centre know that it is made of lightweight steel?
I wouldn’t think so. But when you are inside you know there is something different, as the building feels more livable: it’s cool inside on a hot day even with the air-conditioning off.
Will you be building with lightweight steel frames again?
I definitely feel this is how South Africans will be building in the future and we at BASE Architects & Associates are keen to embrace this and any advances in the building industry.
SOURCE: Leading Architecture & Design