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Off-Site And Modular Construction Explained

What Is Off-Site Construction?

  • Off-site construction involves the process of planning, designing, fabricating, transporting and assembling building elements for rapid site assembly to a greater degree of finish than in traditional piecemeal on-site construction.

  • Off-site building includes a range of materials, scales and systems, digital software, methods of manufacture and fabrication, and innovations in social and technological integration.

  • Off-site outputs include componentized, panellised, and modularised elements deployed in the service of structural, enclosure, service and interior partition systems.

  • An optimising strategy of off-site is to integrate these systems and supply chain through research, design, testing, and prototyping.

Across the spectrum of off-site products, modular, is the most complete in factory finish, up to 95% in some cases, shipped and assembled as 3D volumetric units that are service or structural units to be joined on-site.

The modular industry consists of two distinct industry segments: re-locatable modular and permanent modular. Re-locatable modular, sometimes referred to as temporary modular, are structures which meet temporary space needs and can be leased in a short-term agreement or purchased outright. Job site trailers, temporary classrooms, communication pods, and show rooms are some examples. Although permanent modular construction (PMC) has been flourishing for a decade or more in Europe, it is an emerging market in North America. PMC is comparable to site built structures meeting the International Building Code (IBC), the difference being that it is simply manufactured in chunks within a factory. PMC is deployed for multistory multi-family structures, government buildings, health care facilities, schools, hotels, and any other building types found in traditional on-site construction. Whereas three to four years ago PMC only constituted 25% of the market share in the modular industry, today it represents over 50%.

The modular industry is host to both manufacturers, manufacturer direct, and dealers. Manufacturers produce modules to service general contractors or modular dealers. Manufacturer direct may manufacture for general contractors and dealers, but also contract directly with owners to provide modular solutions, acting as a general contractor. Both manufacturers and manufacturer direct organisations may be specifically focused on a particular building type, residential or commercial for example, or focus on re-locatable and/or permanent construction. Increasingly, however, manufacturers are becoming knowledgeable and skilled across the array of building types, markets, and industry segments.

Modular buildings, temporary and permanent, may be manufactured as structural units that make up the structure of the building once assembled on-site. Non-structural modular such as factory fitted bathroom or service pods can be placed within a larger modular superstructure or in traditional construction on-site.

Modules may be constructed from many different materials including: wood framing, cold-formed steel framing, hot rolled steel, concrete, or a combination of material assemblages. Not all manufacturers will manufacture in many materials; rather manufacturers tend to focus on a particular type of construction to maximize factory efficiencies. The choice of material by stakeholders is usually contingent upon project demands, site forces, and project cost. Further, projects may have a hybrid of material solutions such as traditional site built structure, bathroom modules, or structural modules and a portion of the building that is traditionally site built due to programmatic demands such as large openings, spans or other that are difficult to pre-assemble in the factory.

Modular manufacturing uses an inside out approach to building. Modular frames are constructed as planes, fitted as boxes, and then finished from the inside out. For example, a dormitory unit may follow a sequence of frame, interior surface, electrical, plumbing, mechanical, insulation, exterior sheathing, and cladding. This differs from the traditional on-site assembly sequence of outside in, which restricts the multiple trades that work on top of one another during the build cycle. Factory production of modules avoids the difficulties of unpredictable weather, trades waiting on one another, and incessant delays associated with on-site construction.

The process of modular construction is quite different than on-site construction. This leaves many owners, architects, and builders confused and sometimes put off by the process. Dealers contract for delivery of re-locatable or permanent modular construction, acting as general contractor. With increasingly complex building projects, larger in size and requirement for MEP systems integration, dealers provide knowledgeable project delivery capacity between what is historically identically manufactured re-locatable mods in the temporary modular industry and sophisticated commercial construction solutions in the permanent modular construction industry. Together manufacturers and dealers are creating real value for project teams and building owners who are now embracing this form of construction and delivery.


Off-site construction can service a variety of building and construction types such as education, housing, health care, office, government, dormitory, retail, and hospitality. Off-site is a building process of delivery as much as it is an amalgamation of building products. When understood and deployed by stakeholders intentionally, with early project planning, it is a well-suited solution to control project schedules and budgets while increasing quality and reducing environmental impact. Off-site construction is especially effective when employed to shorten building cycles, on repetitious or unique projects, and with teams that are prepared to embrace the challenges and opportunities associated with its delivery.

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