As the trend for Off-site Construction becomes more popular, there are an increasing number of Clients that opt for this process which brings many advantages. Benefits include predictability, quality assurance, faster construction times, less waste, less noise and disruption to neighbours, less – even zero – defects and lower site accident rates and improved health and safety.
The findings from a study carried out by The Steel Construction Institute, support the view that off-site construction is faster than traditional on-site construction.
There are many attributes to procuring construction materials, elements of construction and finished buildings away from the place where they will be used. Most are favourable to the adoption of these techniques and include:
- Shorter Build times. Time on site depends on the amount of factory produced components and those that are assembled traditionally. Buildings may be constructed from large and small components delivered to site and fabricated by many different trades. Build times are compromised by material and skill shortages and by inclement weather. Buildings that are manufactured in a factory, possibly many hundreds of miles from the site, delivered by road transport and erected on site by crane using skilled assemblers are not subject to these on-site problems.
- Controlled build environment. Factory controlled conditions mean a better quality of build; better finish; fewer defects; all snagging complete and all services tested. These advantages are matched by the skilled workforce who are carrying out the work
- Less noise, dust and local disruption. There can be much annoyance to neighbours caused by traditional building methods usually from noise, dust and litter. With less activity on the construction site the local environment benefits.
- Fewer workmen on site. As most of the work has been carried out off site there is a reduced assembly time on site with fewer tradesmen required.
- Transport from factory to site. Whatever is constructed in the factory has to be transported to the construction site and is dependent upon the limitations of vehicles and available traffic routes. Modular buildings are limited to the sizes that can be lifted and transported safely to site by lorry.
- Cost Plans often take no account of the shorter delivery and erection times; and many benefits are negated by following trades using traditional building methods e.g. precast concrete piles and ring beams are manufactured off-site, delivered and erected. Erection time for precast beams can be measured in minutes while following masonry based trades and roofing take weeks to complete. Other savings can be often found in the reduction of preliminaries, reduced site storage requirements and welfare facilities
- Technological. The use of templates and jigs in a factory environment provides greater accuracy and tolerances particularly when used with CAD design systems
- Reduction in accidents and ill health. Transferring much of the construction programme from an open site to a controlled factory environment reduces on-site time for workers and reduces the potential for site-based accidents and ill health. While this is highly desirable there must also be serious consideration that any site-based risk is not transferred to the factory or somewhere in-between factory and site.