This monthly feature is sponsored by the Modular Building Institute (MBI) Educational Foundation. Tune in each month as we publish different articles on the benefits of Modular Construction. Take the quizzes each month (total of 10) and earn your “Modular Building 101 Certificate” to add to your resume!
TYPES OF CONSTRUCTION
There are two types of commercial modular construction: Permanent Modular Construction (PMC) and Relocatable Buildings (RB).
Permanent Modular Construction is a method of construction, not a building type. It greatly differs from temporary buildings, such as construction trailers or mobile homes. They are custom-designed commercial buildings much the same as their traditional site-built counterparts. In many cases, using PMC does not change the design, structural system, or options for finish materials. The only difference is the method of construction. However, fire codes, transport restrictions, and height restrictions are exceptions that influence the design and structural system. For example, with buildings of a certain height, structural steel becomes more substantial, and units become smaller due to the weight of the steel, fire spray, location or delivery needs.
At the start of the modular building process, the owner needs to engage an architect and a PMC builder at the same time for the greatest project success. The architect should be familiar with aspects pertaining to modular design and be able to work with a PMC builder so that design scope and specifications work seamlessly with constructability issues. Engaging the PMC builder after the design is complete is often too late and often results in the construction drawings being redrawn and re-bid, which can cost the owner additional time and money.
After the design is finalized with an architect, construction plans are sent to a factory where the majority of the building is constructed. PMC uses prefabricated elements for as many building components as possible. Everything from walls and mechanical systems to painting and carpet can be completed on the assembly line.
The difference is that 60% – 90% of modular buildings are completed offsite in a controlled production environment, including most MEP, fixtures, and interior finishes.
While modules are assembled at the factory, site work can begin at the same time, such as laying the foundation or prepping utility connections. This greatly decreases the time needed for total construction. Modular buildings are often completed 30% – 50% faster than conventional structures. In addition to the time savings, the owner also saves money on general conditions because the installation time is shorter on site with PMC, thus creating substantial savings compared to traditional site-built projects. For example, one well-known traditional site-built construction company that turned to modular construction estimated for modular projects, a six-month shorter duration on site could have saved them $100,000/month or $600,000.
Once the modules are ready, they are shipped to the site and fastened together. The final construction stage includes completing material finishes, exterior systems such as cladding and roofing components and internal spaces like lobbies, stairwells, elevator shafts and anything else that is unable to be completed in the factory. The beauty of the finished building is that occupants will not be able to tell how the structure was built.
PERMANENT MODULAR CONSTRUCTION
Permanent Modular Construction process includes offsite construction of modules or building units that are delivered to a single/fixed location. The modules are 60% – 90% completed in a controlled plant environment and then delivered on site. As the name suggests, this construction is a permanent structure and typically will not be relocated as per the owner’s need. Therefore, occupants planning for a long-term stay at one fixed location are best suited for permanent modular construction. Examples of permanent modular construction include healthcare facilities, hotels, schools, and K-12 education facilities.
Relocatable buildings include offsite partial or complete construction of modules in a controlled plant environment. These modules are then delivered as per the owner’s need and can be relocated to different locations. Therefore, occupants planning for a short-term or temporary stay at one location and relocating to different locations are best suited for this type of construction. Examples of temporary modular construction include portable classrooms, offices, structures for emergency housing/disaster relief, etc.
PROS & CONS OF MODULAR CONSTRUCTION
There are many common misconceptions about commercial modular construction:
■ Built to a lower standard of quality
■ Only meet temporary (rather than permanent) needs (i.e., portable classrooms)
■ Can only be moved once
■ Do not follow the same building codes as traditional construction
■ Not affordable
■ Fewer architectural design choices
■ Not sustainable
■ Too new of a construction process
From factory precision to faster installation, modular construction offers an attractive range of advantages and dispels the myths previously mentioned.
Modular has been used, developed and perfected over decades and across all industries (manufacturing, healthcare, institutional and education). Modular units may also be designed to fit in with external aesthetics of an existing building. Thus, once modular units are assembled, they are virtually indistinguishable from their traditional site-built counterparts. After installation, capital improvements to extend the building’s life, such as HVAC or roof replacements, can be made on the same schedule as a conventional building. The same maintenance and inspection requirements common to traditional facilities will also apply to modular buildings.
A primary benefit of modular construction is its fast delivery. Due to the simultaneous process of creating modules in a factory at the same time site work is occurring, modular buildings can often be constructed in half the time as buildings built completely onsite. Factory efficiencies allow building components to be completed quickly and without weather delays. Because the factory has all the key tradespeople to handle construction of the various building components, very few subcontractors are needed when the modules area installed onsite. With the majority of work completed offsite, issues such as noise, dust, debris, and weather complications are greatly reduced. The lower numbers of people, equipment, and traffic at the worksite also decrease the number of construction hazards. All of this makes modular construction suitable for owners who need buildings quickly, properties with hard dates for occupancy, and areas where seasonal weather restricts or even halts construction. It allows the buildings to be occupied sooner and allows owners to see a faster return on investment.
Modular construction makes it possible to optimize construction materials purchasing and usage while minimizing onsite waste and offering a higher quality product to the buyer. According to the UK group WRAP, up to a 90% reduction in waste can be achieved through the use of modular construction. Materials waste minimized includes wood pallets, shrink wrap, cardboard, plasterboard, timber, concrete, bricks, and cement.
The modular structure is constructed off-site simultaneous to foundation and other site work, thereby reducing the time and impact on the surrounding site environment, as well as reducing the number of vehicles and equipment needed at the site.
When the owner’s needs change, some modular buildings can be disassembled and relocated or refurbished for their next use, thus reducing the demand for raw materials and minimizing the amount of energy expended to create a building to meet the new need.
Modular buildings can also contribute to LEED requirements in the same categories as traditional, site-built construction, and can even provide an advantage in the areas of sustainable sites, energy and atmosphere, materials and resources, and indoor environmental quality. Modular construction can also provide an advantage in similar categories in the International Green Construction Code.
Modular construction is process-oriented construction which lends itself to be more efficient. Modular buildings are built with all the same materials and to the same building codes and architectural specifications as traditional onsite construction but in an indoor quality-controlled environment. Just like a car assembly line, a prefabricated building module has built-in quality checks. Modular building factories are dedicated to crafting highly efficient buildings with inspections at each station, eliminating variability in decisions or unexpected complications that can occur in the field.
Because modular units must be trucked long distances and then moved by crane or another method onto a foundation, they must also be extremely structurally sound. Hence, modular buildings can be more durable than structures built onsite.
Other advantages of modular include:
■ More controlled conditions for weather, resulting in fewer delays
■ Material quality maintained in a secure environment
■ Permanent, skilled workforce with extensive training
■ Improved supervision of labor
■ Easier access to tools and fewer material deliveries
■ Assembly of building components off-site while permits are processed and site preparation is taking place
■ Reduced on-site disruption
Disadvantages of Modular Construction
Modular construction is not without its drawbacks. Much like choosing a sustainable building, the decision to use modular construction should be made from the onset of design, although many buildings originally designed for onsite construction have been converted to modular. Because modular construction can change the critical path due to the overlap or simultaneous construction of units and site work, if not scheduled properly, the schedule benefits could be lost.
The advantages of modular construction also decrease considerably if the intended building has no repeating spaces. The prefabrication of entire rooms lies at the heart of modular construction, so a building with custom dimensions or a building with multiple tenants who would finish their own spaces might not be the best candidate for this type of construction. Another disadvantage can be when the design calls for particularly tall ceiling heights. It is not always practical to build large spaces like gymnasiums with modular construction.
Other disadvantages of modular include:
■ Increased engineering requirements for transporting and lifting
■ Decreased ability to make changes during onsite construction phase
■ Local code restrictions and zoning rules might prevent use of modular construction
■ Earlier commitment to engineering and design
■ Increased transportation logistics
■ Steep sites may not suitable for erection of the modules
■ The farther away the construction site is, the more expensive it is to ship modules
■ The design of some modular buildings may be hard to customize
Tune into Instagram next Monday for highlights and hints for the quiz on Week 4!