Offsite and the issue of constructability

(This is part of article that will be published in international confrence in Armsterdam, October 2009)

  • The fundamental idea of offsite is to move some effort away from the construction site to more controlled environment of the manufacturing floor. Offsite is defined as the manufacture and pre-assembly of components, elements or modules before installation into their final location (Goodier & Gibb, 2007).

  • Offsite construction, in addition, is refer to that part of the construction process that is carried out away from the building site, such as in factory or sometimes in specially created temporary production facilities close to the construction site (Gibb & Pendlebury, 2005). The offsite benefits extolled from the specific issues in construction sector such as improvement in quality, cost and time certainty (Pan et al, 2005) to more generic benefits like customer satisfaction and environment (Treadway, 2006).

  • Although, the improvement of constructability is rarely been mention as the benefit of offsite but in theory, offsite can improve constructability by providing designers with the fresh perspective and outlook on the concept of repetition and standardisation. For a long time, repetition and standardisation is bemoan of dull and unattractive design but re-branding effort of offsite recently give a different view in the concept of sensible design where optimisation can go along with trend and awareness on sustainability issue.

  • More important, standardisation allows easier assembly of components with the opportunity for exchange or addition modules thus make sense in term of cost reduction when the mass-production applies (Buildoffsite, 2008).

  • The introduction of modular coordination concept to design offsite components, will improve overall constructability in construction project. Modular coordination is a concept of coordination of dimension and spaces where building and components are dimensioned and positioned in a basic unit or module known as 1 M which equivalent to 100 mm (Hamid et al, 2008). Although modular coordination can be used to design conventional system but it is most associated with offsite and manufactured production components where the element of repetitiveness exists.

  • However, in order to reap the maximum benefit of offsite, one has to synchronize three major function; construction, manufacturing and design. Perhaps, the plausible solution of adopting of offsite principal to improve construction constructability would face several shortcomings particularly on the design integration issues as depicted in the followings:

  • Traditional contracts practice brings the constructors into the project only after the design has been substantially completed and the specification has been developed. No proper channel for constructability input or critiques to improve in design. Constructability input is needed due to high complexity of offsite project

  • Offsite and late design change does not work together. Later design change cannot readily be implemented without influencing the production schedule and extending of time which are the pitfall for every project (NAO, 2005). It is vital to involve designer, supplier, manufacture, architect and client to ensure the development is designed for manufacture and the design suit to manufacture capability and site condition (ibid)

  • The concept of design integration is still new in construction. The nature of construction industry is competitive and fragmented where the genuine collaboration is rare due to the issue of trust

  • There is still lack of designers and professionals trained in offsite and prepared with an offsite skill set to understand the complex harmonisation between offsite design and constructability. The designer had to choose between the designs that could be build with widely available systems in the market or producing specialised design in offsite that will allows aesthetic attribute

  • There is consensus of opinion that to harmonising design and manufacturing capacity lies on the need for early involvement between the design team, manufacturer, contractors and clients (Pan et al, 2008; Sanderson, 2003; Blismas, 2007 and Gibb, 2001). It was commented that offsite need to be integrated from the start of the design process so that the whole design and construction process to be aligned (Goodier and Gibb, 2007). This will eventually lead to a call for better coordination and design integration between all parties involve in offsite construction project (NAO, 2005).

  • The project team needs to be assembled at the beginning of each offsite project to discuss on manufacture capability and constructability in an open collaboration environment. Designers need to have valuable input and critique on the issues of constructability particularly in offsite where the late design change is not a viable option to the project team. There is imperative for the clients to play the role of coordinator to make this thing happen.

  • To achieve design integration during the project implementation, offsite construction team requires real time information between the factory and the project site (Malik, 2006). Information Technology can be a vital and reliable tool to offsite implementation and to integrate design in offsite project. Extensive IT will support tool effectively handles updates change (Lessing, 2005), support integration of design (Oostra & Johnson, 2007) and source for accurate information (Lessing, 2006). Hence, it is good tool for effective production which error of design and incapability of manufacture to produce certain design can be addressed efficiently (ibid).

  • Although, the introduction of offsite construction faced the same problem to adopt constructability as for conventional method, the systems can provide practitioner with the fresh outlook on this issues. Offsite adoption can be a great platform to improve constructability in the sense of standardisation and repetitiveness. More government incentive, research and promotion to generate greater use of offsite, and the issue of constructability can become good drivers for better offsite adoption.

  • On the other hand, offsite can play the role as important tool to enhance constructability particularly with the adoption of extensive IT element in offsite implementation. IT which is enabler in offsite is a vital role to improve more input and critique for constructability particularly at the beginning of the construction project.

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