modular building

Modular building is the assembly of a complete or partial structure from prefabricated units (modules) manufactured in a controlled factory environment, then transported to site and connected together. Each module is typically a three-dimensional box containing finished walls, floors, ceilings, mechanical systems, and sometimes fixtures. Unlike panelized systems that ship flat components, modules arrive at site as load-bearing units ready for rapid stacking and connection.

Modules are built to transport limits: typically 3.5 to 4 meters wide, 2.6 meters high, and up to 20 meters long, constrained by road regulations and bridge clearances. Common materials are timber-framed modules with plasterboard, steel-framed modules for commercial work, and concrete modules for higher density. Each module is completed roughly 80 to 90 percent in the factory, including MEP (mechanical, electrical, plumbing) rough-ins, insulation, and some finishes, then final connections and commissioning happen on-site.

Volumetric modules stack vertically and bolt together at connection points on their frames. Horizontal modules (flat-pack) arrive as open boxes that interlock when assembled. The choice depends on building type: apartments and hotels favor volumetric stacking; schools and hotels may use horizontal modules. Connection details use bolted steel plates, welded connections, or registered mechanical fasteners depending on structural class and local codes.

Where modular fits and where it doesn't

Modular excels in repetitive buildings with short programs: multi-unit residential, student housing, hotels, and modular classrooms. The factory environment controls quality and tolerances tightly, reducing site waste and rework. Schedules compress because foundation and final trades overlap with manufacture. Costs favor projects requiring 20 or more modules; below that threshold, setup costs erode savings. Challenges include transport logistics on congested sites, code compliance across jurisdictions, and retrofitting existing infrastructure connections that don't align with module centers.

The structural frame and floor-to-floor height set module boundaries and drive design constraints. Modules cannot easily accommodate non-standard spans, complex MEP routing between units, or features that cross module lines (large atriums, continuous mechanical systems). Non-modular elements like curtain walls, roofing, and external landscaping still require conventional site labor, so true labor savings depend on scope. Volumetric modules achieve the fastest site time but create thermal bridging at connections unless carefully detailed with insulated splines or thermal breaks.