Prefab Systems + BIM — a Winning Combination

3D Volumetric Components

A 3D volumetric prefab system is a fully outfitted unit that is assembled on-site by lifting each module into place and connecting it with other modules — much like a series of Legos. These units can be a full room or a partial room, and most of the finishing work is completed in a manufacturing facility prior to delivery to the job site.

Pros: Because 3D systems are assembled almost completely off-site in a controlled facility, there is less damage and material waste, no weather delays, and more precision in the assembly process. These systems provide a huge potential for maximum efficiency in terms of time and cost savings.

Cons: 3D units can be BIG — which can sometimes lead to hang-ups around size limitations and potential transportation costs.

Best Use of 3D Systems: Because transporting larger units can be complicated (and often costly), 3D volumetric systems are well suited for hotels, hostels, and affordable housing complexes where the same system can be repeated and installed over and over again. They are also a good choice for spaces that require more intricate finishing work (think “wet rooms” like bathrooms and kitchens), since all of that can be better controlled and protected in a factory environment.

Potential Cost Savings: When evaluating the cost for an affordable housing unit of four floors, McKinsey found that using 3D solutions could be 24% less expensive than a traditional approach.

2D Panelized Components

A 2D panelized system is just what it sounds like — a prefab panel that is delivered to the job site and is then connected with other systems to create different rooms or spaces within a larger structure. Where necessary, panels can come pre-prepped with conduits for services like HVAC, plumbing, and electric for more streamlined on-site assembly.

Pros: Because they’re 2D and can be stacked, prefab panels are typically much easier to transport than 3D units. While you can deliver more materials at a time and at a lower cost, you will have to spend time and money to complete more of the assembly on the construction site.

Cons: While the actual connections between panels are typically simpler than the connections between 3D modules, there is much more piece-by-piece assembly required. Contractors will also have to do more of the internal finishing on the job site while the panels are exposed to the elements.

Best Use of 2D Systems: 2D panelized solutions offer more flexibility than 3D modules. Large, open-plan office spaces are a good example; the point of these structures is for less compartmentalization, which is what 3D systems are most often used for. Regardless of size, 2D panels also work well in custom residential projects where each home is different and the ratio of wet areas to dry areas is lower.

Potential Cost Savings: When evaluating the cost for an affordable housing unit of four floors, McKinsey found that using 2D systems could be 17% less than a traditional approach.

The Hybrid Approach

While some structures feature only 3D modules or only panels, hybrid projects that include a combination of 2D and 3D systems are becoming an increasingly popular option in prefab construction. To use this approach effectively, some design and construction teams are manufacturing bathrooms as 3D pods, and then building the rest of the structure with 2D panels. This optimizes the construction process for the two different areas of the building, brings high-productivity improvements to the bathroom areas, and provides maximum flexibility for all other areas.

Potential Cost Savings: McKinsey found that a 2D and 3D hybrid solution would lower costs by 20%.