Modular construction often brings to mind manufactured homes or job site trailers – cookie cutter buildings that are nothing more than glorified boxes.
What is modular construction?
The term refers to a building process where large sections of a building are built or assembled off-site and are then delivered and installed at the project. Sections can range from wall pieces to entire components, rooms or the full building. They are usually constructed in an indoor manufacturing facilty, where several sections can be worked on simultaneously. They use the same materials, and must build to the same code requirements, as work performed in the field. Components can be assembled off-site more easily, safer, and usually for less money and without added material waste.
There are two main types of prefab construction: permanent modular construction (PMC) and relocatable buildings (RB). PMC buildings, as their name implies, are meant to remain on site once they are installed. They can be single- or multi-story and can include interior finishes as well as shell pieces. RB buildings are more mobile and include construction site offices, medical clinics, and points of sale. Although they are designed to be reused multiple times, they are also designed to meet code requirements.
The projects that most benefit from modular construction are larger projects that have repeating elements. These include hospitals, hotels, multi-family, and office buildings. The elements are built off-site, brought on-site, erected, and then the utilities are connected. The more repeatable the building sections are, the more cost effective it is to use prefabricated construction. Using this technique, buildings can go up in weeks instead of months.
Where can modular construction be used?
On a smaller scale, many mechanical, electrical, and plumbing subcontractors are taking advantage of this technique to save time on-site. They are assembling sections of pipe or ductwork at their shop, and then bringing these assemblies to the site for installation.
Many project sites don’t have the room for storing large amounts of materials as a project progresses. Projects on these types of sites can use modular building to help with logistics, as long as there is enough room to set up for the deliveries and any equipment needed to install the components. In addition, remote sites may be good candidates for modular construction as the building can be assembled off-site where there is an abundance of labor and moved to site. See here for a notable example for a high-end project managed by Stonemark that was built remotely.
Speed construction schedule – Building elements can be built during the site work phase of construction. Once on-site, the modules can be installed in days, instead of weeks. This significantly cuts down the overall construction schedule (up to 30-50%), allowing the owner to move in sooner. Overhead costs are also lower, as crews aren’t on site as long as with traditional construction. Also, there is less chance the project team will have to worry about weather delays slowing down the building construction.
What are the benefits of modular construction?
Higher quality work – The plant environment where components are built allows greater control over quality, both in materials and construction methods. In addition, materials are protected from the weather, which often causes damage to materials left unprotected on-site. Modules are actually constructed to be stronger than their site-built counterparts, as they have to be designed to withstand transportation and lifting.
Less material waste – When built indoors, packaging and scrap materials can be more easily recycled and there is less waste created. Materials are also protected from weather and other damage indoors, leading to less damaged materials having to be thrown away. In addition, modular sections of a building offer the owner the flexibility to disassemble them and reuse them on another building or in another configuration.
Better indoor air quality – Since modular pieces are built in a climate-controlled indoor environment, they don’t get wet from rain and snow during construction. When the pieces are assembled in the plant, there is less moisture present in the assemblies. This helps deter mold growth, dust mites, and other moisture issues that can pollute the indoor air of a building.
Improved safety – Workers build the prefabricated modules indoors, which creates less safety hazards. Workers don’t have to worry about working around open trenches and other site hazards. The building materials can also be manipulated more easily in an indoor environment, lessening body strain from lifting, bending, and reaching. There is less traffic on site as well, cutting down on the chance that there will be accidents.
Lean construction – Lean construction focuses on reducing waste and creating predictable workflows. Modular construction creates less waste and provides a consistent workflow on-site. Deliveries of components can be coordinated for just-in-time delivery, allowing work crews to work more efficiently.
Lower carbon footprint – Less workers on-site means less traffic and less carbon emissions from vehicles and equipment. Less waste going to the landfill and less energy use also reduce the overall carbon footprint of the project.
As computer modeling and BIM allow design teams to be more accurate with their designs, modular construction will continue to gain popularity. The ability to expedite construction schedules, build higher quality buildings, increase safety, and lower the carbon footprint of a project make it an attractive method for any large-scale project that has repeatable elements.