The Waterfall Effect: Cascading efficiency down the construction chain
Faster to construct, producing less waste, able to attain the highest levels of performance, Modern Methods of Construction (MMC) provide many solutions to a range of construction problems.

The classic triangle of time, cost and quality is an inherent frame through which issues of project development can be viewed. Buildings represent high-cost projects where these three critical components impact throughout the construction process. The British construction industry has been notorious for inefficiencies in productivity and quality; both during the construction process, as well as for the final product. The National Audit Office considered that there is potential for around 30 percent improvement in performance. All inputs that go into construction are interrelated, including the tendering process and contractual relationships, however, by tackling one input – building materials - it may be possible to cascade the benefits throughout the construction chain.

 

Widely used in Scandinavia, the Netherlands and other parts of Northern Europe, this article argues that by changing construction practice through the use of structurally insulated panels, multiple benefits can be realised. Barriers obviously exist, however with the correct support both from government and the construction industry, these can be overcome through time.

Time
Construction time: The time from client approval to practical completion impinges heavily on cost as well as quality. In common thinking, the more time there is to design and build, the better - in theory at least - will be the outcome.

This paradigm may hold water in the traditional construction world, where the construction process is highly fragmented from design to build. However, in the world of MMC, there is increasing convergence between the role of contractor and manufacturer. Manufacturers increasingly carry out the role of independent commissioning consultant and therefore shoulder the burden of initial research. When it comes to the build phase using traditional methods, individual components are assembled on site and coordination of subcontractors and delivery of materials partially determines success.

However off-site manufacturing where the components are designed to a high degree of accuracy and either shipped whole to the site or in components, which are then bolted together onsite changes this view. Government reports conclude that onsite times can be reduced by up to 50%.

With a far faster assembling process, the demand for sustained periods of good weather before roofing is installed is substantially reduced. Weatherproof membranes protect the units during transit, if of the volumetric variety. Panels can be transported in containers. Therefore, provided skilled labour is at hand, building components such as roofs can take a fraction of the time of traditional methods required to install.

Additional benefits include requiring fewer structural supports, as these are self-contained, thereby further reducing the amount of time labour needs to spend building the correct structures.

Overruns: The best laid plans of mice and men often go awry, so the saying goes. In construction, this can be for any number of reasons. From a contractor’s perspective, this can include issues such as unforeseen additional requirements. Not only is this a practical headache, contractual grey areas lurk waiting to trap the unprepared.

All too often relations are soured between project participants. With traditional construction practices where the finished product may differ from the design by degrees due to onsite requirements, overruns are estimated to add up to 10% on the time required on site. Although new techniques and materials have reduced the impact of unexpected inclement weather, it is still a significant issue requiring a number of risk abatement measures.

Off-site construction provides a range of solutions, particularly when coupled with a design and build contract.

Firstly, a much greater degree of planning takes place in the factory, which allows a higher degree of accuracy on site. This by itself reduces time-required onsite.

Secondly, because fewer subcontractors are involved with fewer sources of materials, coordination is far easier.

Thirdly, due to the nature of the material, the impact of inclement weather is significantly reduced, particularly with issues such as roof work, which impact throughout the remaining construction. Structurally insulated panels can be in place on the same day.

Disturbance to neighbours: The amount of time on a construction site can create a range of problems, particularly for neighbours. This can include road traffic congestion, air and noise pollution, and unsightliness. In essence, the faster a site is constructed, the less impact there will be on the neighbours.

For housing associations with corporate relationships to maintain with the neighbourhood, this factor is not insignificant. Many local authorities have codes of construction practice, which specify how construction activities must occur and limit certain working practices.

Traffic to and from the construction site can clog the roads, with reductions in parking spaces adding to the potential for conflict. Traditional construction practices require multiple small vehicles – although upon bulk delivery of materials larger vehicles are used - making frequent journeys. In contrast, off site manufacturing requires fewer journeys by larger vehicles. If the site has adequate access, all of the products can be shipped in and offloaded on the same day, with the transport withdrawing accordingly.

Depending upon the type of finish required, off-site manufacturing also has the ability to produce less particulate pollution, as the panels can be wood finished reducing the needs for the mixing of aggregates, and heavy modification onsite.

Cost
Health & safety: Designing out health and safety requirements at the planning stage is key to reducing costs.  Increasingly health and safety regulations are changing techniques used onsite, which inevitably incur additional costs.

The competitive nature of the tender means that where possible costs have been cut and therefore regulation is needed to maintain the level playing field when additional health and safety measures are brought in. Costs, for example, for the use of scaffolding whereas before a simple step-ladder would have sufficed drive up the overall project cost.

Using MMC’s can substantially reduce these additional costs simply by making many safety requirements redundant. With most of the manufacturing carried out in the controlled factory environment, less time is spent on the potentially hazardous site. Once the components or units arrive on site, again, different techniques reduce risk. Building upwards by floor can reduce the need for costly protection equipment required for working at height.

Materials cost: It is often used as justification to avoid MMC. A recent BRE survey shows that MMC typically costs up to 8-15% more than traditional construction techniques.

However, Structural Insulated Panels are generally recognised as providing a solution for around the same cost level as traditional build. Indeed, the survey reported that to achieve EEBPH Best Practice and Advanced Practice of thermal performance, certain MMCs were around 5% cheaper. However, the materials costs of other forms of MMC need to be factored into a whole life cost analysis, which includes labour and operating and maintenance cost of the finished product for a viable comparison.

Labour: Labour costs in recent years has increased due to rising demand. With the government taking the lead in addressing the shortage of new housing the problem could be exacerbated. Although inflationary pressures have eased somewhat in recent months, the release of government land and new mechanisms encouraging home ownership for first-time buyers is likely to see a continued increase in labour costs, as well as difficulties securing skilled labour.

MMC are estimated to save up to 50% of time on site, thereby instantly reducing labour costs. Additionally, it takes fewer labourers to erect the structures further reducing overheads.  

Maintenance & operations: A building can be viewed as an operating system performing a series of functions; shelter, heat and light being the obvious ones. How well the building delivers these services will depend upon how well the system is built.

Tenders awarded on the basis of lowest cost have driven down ongoing building performance, as increased quality of build and materials have been equated with increased cost and thus cut where possible. However, a series of initiatives from government is driving through a more holistic view of buildings.

The Home Information Pack carries a requirement for all sellers to provide details of building performance such as energy efficiency. This is in turn being driven by the EU Energy Performance in Buildings Directive which is set to come into force in January 2006.

In a focus group study for the BRE, house purchasers claimed that energy performance was not considered to be a significant factor until they were shown the cost benefits of certain performance over others.  The energy performance of buildings was then considered to be significant, particularly in negotiating stages of price settlement. A house with higher energy efficiency could save tens of thousands of pounds in avoided fuel bills over its lifetime.

MMCs can provide the specified levels of thermal insulation to order. Therefore it is possible for the developer to demonstrate added value to the property during the sales process. 

Quality
Environmental impacts: Construction and demolition waste accounts for around 25% of the UK’s waste according to government statistics . While studies are somewhat lacking in detail, it is generally accepted that the higher accuracy of the design and manufacture process in the factory can significantly reduce the amount going to landfill or other disposal methods. With increasing tariffs on waste, this reduction has a direct impact on the project’s bottom-line.

Localised pollution in terms of dust particles is also reduced significantly due to the lack of much cutting required onsite. Factories themselves have the ability to extract and capture whatever dust is created rather than releasing it into the environment.

Transport effects are also thought to be reduced, although again no detailed analysis appears to have been carried out. In terms of ensuring least environmental impact from procurement of sustainable materials, the developer can have a greater confidence in the standards of accreditation of the material, particularly timber.

Post-construction: With many of the problems associated with snagging designed out, the additional costs and associated problems arising with retro-fixing a problem are largely done away with.  In addition, with the buildings specs achieving a high degree of accuracy when translating into the construction phase, costly retrospective alterations in order to comply with Building Control should be minimised.

Summary
Despite the numerous benefits posed by MMC, the much-cited chief barrier remains a lack of significant demand. While the current manufacturers promote themselves as best they can, serious investment into the sector will most likely be driven by regulation that changes the inertia in the construction industry. While this may come in the form of government targets, there is an immediate opportunity to start the ball rolling through a campaign of education and awareness raising. It seems that the market has not even moved to capture all the early adopters. Here the government can play a part, as it is beginning to do through its Constructing Excellence and Challenge Fund initiatives. More is needed to educate developers, in order to turn the sensibilities of MMC into common property.