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Tip Two – Getting Started with “Off-site Construction”

In this blog series of “Getting started with Off-site Construction”, we continue to talk about working with off-site construction techniques and how to realize the best possible outcome. More and more architects, owners, construction managers and general contractors are hearing the benefits of building off-site in a controlled environment, and they have a better understanding as to how the process works thanks to the media spotlight on modular construction projects from around the world.  Here is the second of three basic pre-construction tips on how to work with off-site construction techniques.

TIP TWO Commit to the Concept; Complete the Design.

A successful modular project requires some advance collaborative planning to avoid pitfalls that can occur when attempting to convert a conventionally designed building project over to a modular project too late in the game.  The design team should consult with or include a qualified modular contractor who can guide the design process and optimize the use of modularization.  While permanent modular construction can meet most any requirements for aesthetics, building science, mechanical and electrical systems, life safety and life cycle durability – there are certain conditions inherent to the elemental design principles that need to be considered.

  1. The Module layout. Breaking the desired floor plan down into workable modules requires planning. The module layout is determined by creating the most logical and cost efficient way to achieve the desired floor plan for the owner, while allowing for all outside influences that impact, or are impacted by this design.  Some examples include:
    • Foundations. The final module layout determines the final foundation design requirements by establishing all bearing point locations and their loads
    • Transportation regulations.  Each three-dimensional module must travel over roads from the plant to the final site location and local transportation regulations, (they can vary geographically), will govern the maximum length, width and height these pieces can travel.  High volumetric spaces such as mine dry facilities with hanging locker basket systems would require the modules be split both horizontally and vertically.
    • Site access. Notwithstanding the restrictions that may be imposed by transportation, the modules must also be able to move through the site location, and be craned on to the foundations.   Fencing, gates, adjacent structures and other obstructions must be considered when establishing the final sizes and configurations of the modules, or when determining the extent of site work that may be necessary.
    • Mechanical /Electrical Systems. Because overall height of module is also dictated by transportation, often mechanical duct systems are designed to work within less ceiling space.   BIM is an effective tool to assist with layouts and clash detection.
    • Modular mate lines. The objective is to complete as much of the building off site as possible, up to 90% is common.  Therefore when configuring the modular floor plan it is best to avoid locating windows, doors and plumbing fixtures across modular splits if possible, to reduce on-site work.

The module layout needs to be completed by the modular builder, with the input of other stakeholders in the event some minor changes are needed. The final Modular Key Plan as it is commonly known, is then “frozen” and becomes an essential part of the structural design process.

  1. Final Design and Approvals. When formulating the project schedule, establish a reasonable but finite time to get the final design, submittals and approvals completed to 100% and stay with it. Unlike conventional construction where the length of the project schedule may permit decisions or changes to be made during construction, once the modular project hits the plant floor, contemplated changes, or change directives can adversely affect the flow of the construction process, and the schedule.

In order to gain the optimal advantage of the accelerated scheduling, the objective is to avoid discontinuance, so capturing the complete design intent and code requirements upstream is necessary.  The modular builder may also ask for staged approvals that best fit their production schedule, particularly for items on the critical path such as structural steel, so be prepared to review and approve the shop drawings as they are submitted.