Modular construction is the process of building parts of, or an entire building, off site in a separate factory as finished three-dimensional modules, which are then transported and craned into place. Done well, this construction method offers benefits such as improved quality control, a shorter schedule and less rework.
How modular construction works
- The design is developed around module sizes that can be built, shipped and lifted, and is frozen earlier than on a site-built job.
- Foundations and site services are built on site while modules are made in the factory at the same time.
- Modules are fitted out in the factory, often including finishes, plumbing and electrical, and inspected there.
- They are trucked to site, set by crane and connected structurally and through the MEP services.
- Seams between modules (often called marriage lines), roofs, cladding and common areas are finished on site.
Types of modular construction
| Type | What it is |
|---|---|
| Volumetric modules | Factory-built 3D units such as hotel rooms, apartments or classrooms |
| Panelized | Flat wall, floor and roof panels made in a factory and assembled on site |
| Hybrid | Modules for wet or service-heavy areas combined with panels or a site-built frame |
| Pods | Complete bathroom or kitchen units dropped into an otherwise conventional building |
| Permanent vs relocatable | Permanent modular buildings stay on their foundations; relocatable buildings are designed to be moved and reused |
Advantages and disadvantages
Advantages:
- Site and factory work run in parallel, shortening the schedule
- Factory conditions improve quality control and reduce weather delays
- Less waste and fewer workers and deliveries on site
Disadvantages:
- Transport size limits and road permits restrict module dimensions
- Design must be fixed early; late changes are costly
- Large cranes, laydown space and good access are needed
- Factory deposits and payment terms can strain project financing
Modular vs prefab vs manufactured
Prefabrication is the umbrella term for anything built off site, from trusses to precast panels. Modular construction is the volumetric end of prefab. In the US, a modular home is built to the same state and local building codes as a site-built house, while a manufactured home is built to the federal HUD code, traditionally on a permanent steel chassis.
Related terms
Related templates and guides
- Everything You Need To Know About Modular Construction
- Modular Construction – The Essential Guide For Architects
- Modular Construction: From Projects to Products
- Saving Time With Modular Bathroom Pods
- How To Plan Your Next Construction Crane Lift
Frequently asked questions
Is modular construction cheaper?
Not always. The most reliable saving is time, because site and factory work overlap. Direct cost depends on how repetitive the design is, transport distance, crane costs and local labour rates. Repetitive buildings such as hotels, student housing and apartments usually benefit most.
What is the lifespan of a modular building?
A permanent modular building is designed and built to the same codes as a comparable site-built building, so it is expected to last as long when properly maintained. Relocatable modular buildings are designed for temporary use and repeated moves, and usually have a shorter intended life.
What are the disadvantages of modular construction?
Module sizes are limited by road transport, design decisions must be made early, cranes and site access are critical, and factory payment terms can complicate financing. Poorly detailed connections between modules can also cause problems with fire separation, acoustics and water tightness.
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