Light Steelframe Construction
Over the past decade steel frame construction has significantly increased due to the benefits of performance, speed, ease of use and quality of construction that arise from the off-site nature of the construction process important in urban and/or mix-used buildings.
Steel is a lightweight construction system which minimizes the load on the foundations, and therefore saves on sub-structure costs. It is mainly used
The main market for steel in this sector is in multi-storey residential buildings, and particularly buildings of mixed-use, where the lower levels are for commercial use or, in some cases, for basement car parking. For mixed-use buildings, the compatibility of floor grids between the commercial, car parking and residential levels is a key factor in the design solution and is more easily achieved using steel construction. Modular or volumetric construction has also achieved a high market share in the construction of student residences and hotels, where an economy of scale in manufacture of the modules can be achieved.
A variety of steel building technologies may be used in this sector, including structural steel frames, Infill walling, floor decking, lightweight façade and roofing systems, and modular systems. There is a strong supply chain for delivery of these technologies into the residential building market.
The benefits of steel in residential and mixed use buildings are summarised as follows:
Speed of construction
All steel construction uses pre-fabricated components that are rapidly installed on site. Short construction periods leads to savings in site preliminaries, earlier return on investment and reduced interest charges. Speed of construction in urban residential projects is important to minimise disturbance to adjoining properties.
Flexibility and adaptability
Steel-framed systems using infill and separating walls are inherently flexible in terms of their location on plan and can be meet a variety of apartment layouts. They can be reconfigured in the future to meet new demands or even change of use. Modular systems can be dismantled and moved, thereby maintaining the asset value of the building.
Steel structures weigh less than half of an equivalent concrete structure and light steel framing or modular systems weigh less than a quarter of a concrete structure, which saves on foundation costs, and on the supporting podium costs in a mixed-use building.
Quality and safety
Off-site prefabrication improves quality by factory controlled production, and reduces dependency on site trades and the weather. Working in a controlled, manufacturing environment is substantially safer than working on site. The use of pre-fabricated components reduces site activity for frame construction by up to 75%, thereby substantially contributing to overall construction safety.
Fire safety during construction is an important consideration and one which has adversely affected timber framing. Steel construction is inherently non-combustible and does not add to the fire load.
Many of the intrinsic properties of steel usage in construction have significant environmental benefits. For example, the steel structure is 100% recyclable, repeatedly and without any degradation; the speed of construction and reduced disruption of the site gives local environmental benefits.
Economic benefits of steel construction in residential buildings Factor Improvement Economic benefit
Speed of construction 20 to 40% reduction in construction time relative to site-intensive construction, depending on the scale of the project The economic benefit depends on the type of project- for example, a student residence has to be delivered often within one academic year. For residential buildings, an individual apartment cannot be occupied until the building is complete and so there is an imperative for speed of construction in terms of cash flow
Site management costs Site management costs are reduced because of the shorter construction period Site management costs can be reduced by 20 to 30% which can lead to a 3 to 4% saving in terms of overall building cost
Minimum floor to floor height Slim floor systems have been developed to minimise the overall floor zone to as little as 400mm including a resilient floor covering and ceiling A 5% reduction in floor to floor height can lead to one additional floor in 20, and to a similar reduction in cladding cost, which is equivalent to about 1% in total building cost. Floor to floor height often must conform to multiples of brick dimensions e.g. 2850 mm
Foundations Steel construction is less than half the weight of an equivalent concrete structure, which is equivalent to a 30% reduction in overall foundation loads Foundation costs for residential buildings represent 5 to 10% of the building cost. A 30% reduction in foundation loads can lead to a 1.5 to 3% overall saving in terms of construction cost
Mixed-use buildings Long span steel construction at the podium level provides more flexible use of space below, which depends on the function of the building The lightweight nature of the steel structure of the upper residential levels minimises the loads on the podium level and therefore saves on the cost of the podium structure