NEW RESEARCH CONFIRMS REINFORCED CONCRETE'S COST ADVANTAGES

New research has found that, when comparing the costs of additional finishes necessary for a building’s operational performance, reinforced concrete with its wide range of inherent benefits can be up to 30% cheaper than rival construction materials. The research findings will be presented at a British Association of Reinforcement industry seminar on 30th September.

The research, ‘Critical analysis of building performances and cost comparison of reinforced concrete, steel and timber framed building’ was undertaken by the University of Greenwich. It is unusual in that whilst there have been a number of cost comparison studies comparing the costs of actual construction, these do not examine the costs of the additional finishes for occupational performance. There is much anecdotal evidence of the inherent benefits of reinforced concrete – for example: fire resistance, flood resilience, sound insulation – but no specific studies of the extra cost of the additional finishes necessary for steel and timber construction to offer the equivalent performance.

With this in mind, the British Association of Reinforcement (BAR) invited the University of Greenwich to undertake independent research to determine and quantify if the supposed inherent benefits of reinforced concrete translate into real cost advantages over steel and timber.

The research focused on eight critical additional performance costs: acoustic insulation; fire protection; thermal insulation; insurances; vibration performance; energy efficiency; maintenance; robustness. It found that for reinforced concrete the cost was either zero or low.

Acoustic and thermal insulation play a major role in occupant comfort. Concrete construction is known for providing excellent levels of acoustic and thermal mass at no extra cost. In terms of fire protection, concrete is inherently fire resistant and offers up to 4 hours free fire protection. Steel although is inherently non-combustible can lose much of its structural strength when heated to extreme temperatures and timber requires considerable additional fire protection in order to provide equivalent fire resistance. Timber also provides less robustness when compared with concrete and steel and can result in high on-going maintenance costs resulting from flood damage or fungal and insect attack. The range of inherent performance benefits means that concrete buildings are often cheaper to insure. Indeed, the research quote a 2017 study carried out by VanderWerf and Haidari that found commercial property insurance can be 40% cheaper for concrete buildings whilst builder’s risk insurance is some 47% cheaper.

The research consists of 4 stages: systematic review; documentary analysis; systematic cost analysis and final synthesis.

The systematic review included a critical review and performance cost analysis of the reinforced concrete, steel and timber construction. This resulted in a number of comparative tables which enabled documentary analysis to be carried out on an identical building using the different construction materials. The overall building costs per metre square was estimated for each option. This led to the third stage of the research which focused on cost analysis using the Royal Institution of Chartered Surveyors (RICS) Building Cost Information Service (BCIS). BICS is a cost data-based system that collates past project analyses of UK projects. It also provides data to enable cost forecasting and cost planning. The research used BICS to establish to frequency use of concrete, steel and timber-framed construction for five main categories of buildings and then carry out an analysis of the average cost of m2. Local factors and tender price index adjustments were considered to ensure a fair comparison. This included a further analysis to simulate if the projects had been built in December 2020 (4Q 2020).

The final stage of the process was to provide a synthesis of the previous 3 stages to allow a final comparison of average cost per m2. This found that when taking account of the additional cost of performance finishes, concrete frame construction was some 31% cheaper than steel frame construction. See the table below:

The study by Greenwich University is arguably the first that provides a detailed cost comparative analysis and discussion of the performance benefits of different construction materials that can reduce both building construction and ongoing costs. It recognises the range of free benefits of concrete construction and underlines the need to fully consider the additional performance costs of other construction materials when determining the real overall cost of a building’s construction.

To download a copy of ‘Critical analysis of building performance benefits and cost comparison of reinforced concrete, steel and timber framed building’ visit: www.uk-bar.org/publications