Along with fragmenting design and building teams, conventional construction takes place in a linear process. Planning (design, financing, and budgets) is followed by construction document production by licensed professionals, open tendering, contracting, building, and commissioning. Tasks are sequenced and managed onsite until the finished building is handed over to its owner, who mandated a general contractor to complete the project as designed by the retained professionals. Within the process, subtrades are also contracted and made responsible for their coordination and adjustments in line with construction documents provided to them, often with little description or explanation. In opposition to this, offsite construction proposes a process that begins the manufacturing of sub-assemblies in parallel with site work and that includes manufacturing criteria in the planning process.
The overlapping of manufacturing tasks with onsite construction has been clearly established as one of prefabrication’s most notable advantages, as the shortening of a project’s timeline reduces everything from construction management costs and borrowing costs to construction waste, and the number of production days. Handover of the finished product and making it useful for the owners happens quicker than for onsite-built edifices. Project acceleration can also lead to a decreased environmental footprint, as worker-hours travelled to and from the building site are minimized. While these potential advantages are not subject to debate, the cost of ensuring they are realized is greater upfront planning. This planning should include a collaborative framework that puts manufacturers in the design phase of a project for professionals to consider manufacturing logistics and criteria. Good communication is the key with all design stakeholders to predefine and coordinate structural, architectural, and mechanical systems.
Respecting manufacturing possibilities from the start also implies construction documents, drawings and specs, that outline their specificities. Transport criteria can define structural grids, along with modularity, and material supply chains can limit design choices. Material constraints, coordination responsibilities, infrastructure connections, and site versus offsite assignments must all be established upstream. This intensive upfront planning upends conventional construction methodologies, and increases design costs but can lead to efficient and cost cutting timeline compressions in the long run. Repeating this harmonized process and team-based design, while considering manufacturing, adds value to individual projects and for serial production can lead to even greater economies by spreading costs over multiple projects.
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| Traditional planning versus planning with Offsite construction |
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