Modular construction

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Algeco school built using pre-fabricated modular construction Algeco school modular building.jpg
Algeco school built using pre-fabricated modular construction

Modular construction is a construction technique which involves the prefabrication of 2D panels or 3D volumetric structures in off-site factories and transportation to construction sites for assembly. This process has the potential to be superior to traditional building in terms of both time and costs, with claimed time savings of between 20 and 50 percent faster than traditional building techniques. [1]

Contents

It is estimated that by 2030, modular construction could deliver US$22 billion in annual cost savings for the US and European construction industry, helping fill the US$1.6 trillion productivity gap. [1] The current need for standardized, repeatable 3D volumetric housing pre-fabricated units and designs for student accommodations, affordable housing and hotels is driving demand for modular construction.

Advantages

In a 2018 Practice Note, the NEC states that the benefits obtained from offsite construction mainly relate to the creation of components in a factory setting, protected from the weather and using manufacturing techniques such as assembly lines with dedicated and specialist equipment. [2] Through the use of appropriate technology, modular construction can:

Disadvantages

In contrast to the benefits mentioned earlier, modular construction presents two significant obstacles: [3]

Time

Modular construction has consistently been at least 20 percent faster than traditional on-site builds.[ citation needed ] Currently, the design process of modular construction projects tends to take longer than that of traditional building. This is because modular construction is a fairly new technology and not many architects and engineers have experience working with it. In fewer words, the industry has not yet learned how to work this way. It is expected of design firms to develop module libraries which would assist in the automation of this process. These modules libraries would hold various pre-designed 2D panels and 3D structures which would be digitally assembled to create standardized structures.

The foundations of a structure are a crucial part of its rigidity. The magnitude and complexity of such will vary depending on the size, and overall weight of the structure. Therefore, the weight difference of a traditionally built house and a prefabricated structure will mean that foundations needed will be smaller and faster to build.

Off-site manufacturing is the pinnacle of modular construction. The ability to coordinate and repeat activities in a factory along with the increased help of automation result in largely faster manufacturing times than those of on-site building. A large time saver is the ability to parallelly work on the foundation of a structure and the manufacturing of the structure itself. This would be impossible with traditional construction. The on-site construction is radically simplified. The assembly of pre-fabricated components is as simple as assembling the 3D modules, and connecting the services to main site connections. A team of five workers can assemble up to six 3D modules, or the equivalent of 270 square meters of finished floor area, in a single work day.

Production algorithms

Since the technology required to manufacture the components of modular construction, the prefabricated parts of modular buildings are carried out by modular factories. To optimize time, modular factories consider the specifications and resources of the project and adapt a scheduling algorithm to fulfill the needs of this unique project. However, current scheduling methods assume the quantity of resources will never reach zero, therefore representing an unrealistic work cycle.

A modular factory handling a single project at any given point is rare, and would produce low returns. Hyun and Lee's research propose a Genetic Algorithm (GA) scheduling model which takes into consideration various project's characteristics and shares resources. [4] The production sequence of this algorithm would be largely affected by which modules need to be transported to which site and the dates they should arrive. After considering the variables of production, transportation and on-site assembly the objective function is:

Where Si is the number of stocked units per day, Pi is the number of units per day and Ei is number of units installed per day. Production algorithms are continuously being developed to further accelerate the production of modular construction buildings, enlarging the time saving gap with traditional construction methods.

Cost

Modular construction can yield up to 20 percent of the total project cost in savings. However, there is also a risk of it increasing the cost by 10 percent.[ citation needed ] This occurs when the savings in the labor area of construction are outweighed by the increase in costs of the logistics area and materials. The pre-fabrication of components used in modular construction have a higher logistics cost than traditional building. Since the panels or 3D structures have to be manufactured in a factory and transported to the construction site, new variables which alter the flow of construction are presented.

Transportation

Transportation of fabricated components is naturally more expensive than that of raw materials. For one, even a number of 2D panels stacked together are much harder to transport than the raw cement, wood or material used to build them. Panels run a high risk of suffering minor or major damage when being transported through land. If a panel were to be damaged, it would likely have to be replaced entirely. The factory would need to temporarily stop production of other panels to replace this one, increasing the overall manufacturing hours and therefore cost. On top of the manufacturing hours, the transportation hours would also be increased, increasing yet another cost. Regardless, the transportation of 2D panels is still a good alternative to on-site construction.

Transportation reaches its peak cost when shipping 3D volumetric structures. While 1 m2 of 2D floor space takes approximately US$8 to transport 250 km, its equivalent in 3D floor space takes US$45. [1] Adding to this the replacement cost if the structure gets damaged during transport creates a large cost increase.

Construction

Assembling components in a factory off-site means that workers can use the repeatability of the structures as well as the use of automation to facilitate the manufacturing process. By standardizing the overall design of structures, work which would usually require expensive workers with specific skills (e.g. mechanical, electrical and plumbing) can be completed by low-cost manufacturers, decreasing the total salaries cost. As very little manufacturing occurs on-site, up to 80% of traditional labor activity can be moved off-site to the module factory. This leads to a lower number of sub-contractors needed, further decreasing overall total salaries cost. Overall, the larger the labor-intensive portion of a project, the larger the savings will be if modular construction is used.

Project such as student accommodations, hotels and affordable housing are great candidates for modular construction. The repeatability of their structures leads to faster manufacturing times and therefore less overall cost. Meanwhile, if the project is (for example) a modern beach house with highly irregular wall spaces and ceilings, traditional construction methods may be preferable. As the industry continues to adapt and grow, these repeatable designs could one day be modified and adapted to fit all kinds of structures at decreased costs.

Safety

Construction is considered to be one of the most dangerous industries. Workers fall from heights, objects are dropped, muscles are strained and environmental hazards can be found. Modular construction constrains all manufacturing activities to a ground level, clean space with fewer workers needed. It is estimated that reportable accidents are reduced by over 80% relative to site-intensive construction. [5] When asked in a survey about safety management in the construction industry conducted by McGraw Hill Construction in 2013, 50% of the construction industry believed that pre-fabrication was safer than traditional on-site building, while only 4% said that prefabrication or modular construction had a negative impact on safety performance. Of the general and specialty contractors surveyed, 78% and 59% said that the largest safety impact was the undergoing of complex tasks at ground level. [6] According to the CDC, falling is the leading cause of work-related fatalities in construction, making up more than one in every three deaths in the industry. [7] The reduction of heights at which workers need perform tasks on subsequently reduces the fatality risk they experience, greatly increasing the overall safety of the industry.  Also, 69% of the general contractors as well as 69% of the specialty contractors mentioned that the reduced number of workers performing different tasks at the off-site factory also improved construction site safety. Overall, modular construction is safer for the following reasons:

Modular construction is still not considered an entirely safe alternative. However, it does reduce accidents and fatalities by a significant amount. Especially in the manufacturing process of a project. 48.1% of all accidents during on-site construction were fall-related, while only 9.1% of the accidents at manufacturing plants were from falls. [6] Manufacturing plant workers were more likely to be struck by an object or equipment (37.1%) and fracture and amputation had the same injury type frequency at 27.3%. Nevertheless, as the construction industry continues to adapt and moves over to more sustainable construction methods like pre-fabricated modular construction, it is expected that the overall safety number of accidents at construction sites will decrease.

The use of modular construction methods is encouraged by proponents of Prevention through Design techniques in construction. It is included as a recommended hazard control for construction projects in the "PtD - Architectural Design and Construction Education Module" published by the National Institute for Occupational Safety and Health. [7]

Sustainability

Modular construction is a great alternative to traditional construction when looking at the amount of waste each method produces. When constructing a high-rise building in Wolverhampton, 824 modules were used. During this process about 5% of the total weight of the construction was produced as waste. If it is compared to traditional methods' 10-13% average waste a small difference can be observed. [5] This difference may not seem like much when talking about small structures, however when talking about a 100,000 lb/ft2 building it is a significant percentage. Also, the number of on-site deliveries decreased by up to 70%. [5] The deliveries are instead moved to the modular factory, where more material can be received. On-site Noise pollution is greatly reduced as well, by moving the manufacturing process to an off-site factory, usually located outside of the city, neighboring buildings are not impacted as they would with the traditional building process.

Modular construction systems

Open-source and commercial hardware components used in modular construction include: open beams, bit beams, maker beams, grid beams, contraptors, OpenStructures components, etc. [8] [9] Space frame systems (such as Mero, Unistrut, Delta Structures, etc.) also tend to be modular in design. [10] Other materials used in construction which are interlocking and thus reusable/modular in nature include interlocking bricks. [11] [12] [13]

See also

Related Research Articles

<span class="mw-page-title-main">Space frame</span> Rigid three dimensional load bearing truss structure

In architecture and structural engineering, a space frame or space structure is a rigid, lightweight, truss-like structure constructed from interlocking struts in a geometric pattern. Space frames can be used to span large areas with few interior supports. Like the truss, a space frame is strong because of the inherent rigidity of the triangle; flexing loads are transmitted as tension and compression loads along the length of each strut.

Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a system into varying degrees of interdependence and independence across and "hide the complexity of each part behind an abstraction and interface". However, the concept of modularity can be extended to multiple disciplines, each with their own nuances. Despite these nuances, consistent themes concerning modular systems can be identified.

<span class="mw-page-title-main">Modular building</span> Prefabricated building or house that consists of repeated sections

A modular building is a prefabricated building that consists of repeated sections called modules. Modularity involves constructing sections away from the building site, then delivering them to the intended site. Installation of the prefabricated sections is completed on site. Prefabricated sections are sometimes placed using a crane. The modules can be placed side-by-side, end-to-end, or stacked, allowing for a variety of configurations and styles. After placement, the modules are joined together using inter-module connections, also known as inter-connections. The inter-connections tie the individual modules together to form the overall building structure.

<span class="mw-page-title-main">Structural insulated panel</span>

A structural insulated panel, or structural insulating panel, (SIP), is a form of sandwich panel used in the construction industry.

Prefabrication is the practice of assembling components of a structure in a factory or other manufacturing site, and transporting complete assemblies or sub-assemblies to the construction site where the structure is to be located. Some researchers refer it to “various materials joined together to form a component of the final installation procedure“.

<span class="mw-page-title-main">Prefabricated home</span> Type of prefabricated building

Prefabricated homes, often referred to as prefab homes or simply prefabs, are specialist dwelling types of prefabricated building, which are manufactured off-site in advance, usually in standard sections that can be easily shipped and assembled. Some current prefab home designs include architectural details inspired by postmodernism or futurist architecture.

<span class="mw-page-title-main">Formwork</span> Molds for cast

Formwork is molds into which concrete or similar materials are either precast or cast-in-place. In the context of concrete construction, the falsework supports the shuttering molds. In specialty applications formwork may be permanently incorporated into the final structure, adding insulation or helping reinforce the finished structure.

<span class="mw-page-title-main">Manufactured housing</span> Type of prefabricated housing

Manufactured housing is a type of prefabricated housing that is largely assembled in factories and then transported to sites of use. The definition of the term in the United States is regulated by federal law : "Manufactured homes are built as dwelling units of at least 320 square feet (30 m2) in size with a permanent chassis to assure the initial and continued transportability of the home." The requirement to have a wheeled chassis permanently attached differentiates "manufactured housing" from other types of prefabricated homes, such as modular homes.

<span class="mw-page-title-main">Modular design</span> Design approach

Modular design, or modularity in design, is a design principle that subdivides a system into smaller parts called modules, which can be independently created, modified, replaced, or exchanged with other modules or between different systems.

<span class="mw-page-title-main">Deconstruction (building)</span>

In the context of physical construction, deconstruction is the selective dismantlement of building components, specifically for reuse, repurposing, recycling, and waste management. It differs from demolition where a site is cleared of its building by the most expedient means. Deconstruction has also been defined as "construction in reverse". Deconstruction requires a substantially higher degree of hands-on labor than does traditional demolition, but as such provides a viable platform for unskilled or unemployed workers to receive job skills training. The process of dismantling structures is an ancient activity that has been revived by the growing fields of sustainable and green building.

<span class="mw-page-title-main">Precast concrete</span> Construction material

Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and maneuvered into place; examples include precast beams, and wall panels for tilt up construction. In contrast, cast-in-place concrete is poured into site-specific forms and cured on site.

<span class="mw-page-title-main">Prefabricated building</span> Building constructed using prefabrication

A prefabricated building, informally a prefab, is a building that is manufactured and constructed using prefabrication. It consists of factory-made components or units that are transported and assembled on-site to form the complete building. Various materials were combined to create a part of the installation process.

An industrial control system (ICS) is an electronic control system and associated instrumentation used for industrial process control. Control systems can range in size from a few modular panel-mounted controllers to large interconnected and interactive distributed control systems (DCSs) with many thousands of field connections. Control systems receive data from remote sensors measuring process variables (PVs), compare the collected data with desired setpoints (SPs), and derive command functions that are used to control a process through the final control elements (FCEs), such as control valves.

<span class="mw-page-title-main">Cross-laminated timber</span> Wood panel product made from solid-sawn lumber

Cross-laminated timber (CLT) is a subcategory of engineered wood with panel product made from gluing together at least three layers of solid-sawn lumber. Each layer of boards is usually oriented perpendicular to adjacent layers and glued on the wide faces of each board, usually in a symmetric way so that the outer layers have the same orientation. An odd number of layers is most common, but there are configurations with even numbers as well. Regular timber is an anisotropic material, meaning that the physical properties change depending on the direction at which the force is applied. By gluing layers of wood at right angles, the panel is able to achieve better structural rigidity in both directions. It is similar to plywood but with distinctively thicker laminations.

Offsite construction refers to the planning, design, manufacture and assembly of building elements at a location other than their final installed location to support the rapid speed of, and efficient construction of a permanent structure. Such building elements may be prefabricated offsite in a different location and transported to the site or prefabricated on the construction site and then transported to their final location. Offsite construction is characterized by an integrated planning and supply chain optimization strategy. Offsite manufacturing (OSM), offsite production (OSP) and offsite fabrication (OSF) are terms used when referring primarily to the factory work proper.

<span class="mw-page-title-main">Prefabs in the United Kingdom</span>

Prefabs were a major part of the delivery plan to address the United Kingdom's post–World War II housing shortage. They were envisaged by war-time prime minister Winston Churchill in March 1944, and legally outlined in the Housing Act 1944.

A relocatable building is a partially or completely assembled building that was constructed in a building manufacturing facility using a modular construction process. They are designed to be reused or repurposed multiple times and transported to different locations. Relocatable buildings can offer more flexibility and a much quicker time to occupancy than conventionally built structures. They are essential in cases where speed, temporary swing space, and the ability to relocate are necessary. These buildings are cost effective, code compliant solutions for many markets.

Commercial Modular Buildings are code-compliant, non-residential structures that are 60% to 90% completed offsite in a factory-controlled environment. They are then transported or shipped to a final destination where the modules are then erected onto a concrete foundation to form a finished building. The word "modular" does not describe a building type or style; it simply describes a means of construction.

<span class="mw-page-title-main">Manufacture of the International Space Station</span> Fabrication of the ISS elements

The project to create the International Space Station required the utilization and/or construction of new and existing manufacturing facilities around the world, mostly in the United States and Europe. The agencies overseeing the manufacturing involved NASA, Roscosmos, the European Space Agency, JAXA, and the Canadian Space Agency. Hundreds of contractors working for the five space agencies were assigned the task of fabricating the modules, trusses, experiments and other hardware elements for the station.

The industrialization of construction is the process through which construction aims to improve productivity through increased mechanization and automation. The process commonly involves modularization, prefabrication, preassembly, and mass production.

References

  1. 1 2 3 Bertram, Nick (2019). Modular construction: From projects to products. McKinsey & Company.
  2. ↑ NEC, Offsite modular construction, Practice Note 4, published September 2018, accessed 15 November 2020
  3. ↑ Jayson Maina. "The A to Z of Modular Construction". Construction Kenya. Retrieved 26 July 2023.
  4. ↑ Lee, Jeonghoon; Hyun, Hosang (2019-01-01). "Multiple Modular Building Construction Project Scheduling Using Genetic Algorithms". Journal of Construction Engineering and Management. 145 (1): 04018116. doi:10.1061/(ASCE)CO.1943-7862.0001585. ISSN   1943-7862. S2CID   116344719.
  5. 1 2 3 Lawson, R. Mark; Ogden, Ray G.; Bergin, Rory (2012-06-01). "Application of Modular Construction in High-Rise Buildings". Journal of Architectural Engineering. 18 (2): 148–154. doi:10.1061/(ASCE)AE.1943-5568.0000057.
  6. 1 2 Fard, Maryam Mirhadi; Terouhid, Seyyed Amin; Kibert, Charles J.; Hakim, Hamed (2017-01-02). "Safety concerns related to modular/prefabricated building construction". International Journal of Injury Control and Safety Promotion. 24 (1): 10–23. doi:10.1080/17457300.2015.1047865. ISSN   1745-7300. PMID   26105510. S2CID   40719364.
  7. 1 2 "CDC - NIOSH Publications and Products - PtD - Architectural Design and Construction - Instructor's Manual (2013-133)". www.cdc.gov. 2013. doi: 10.26616/NIOSHPUB2013133 . Retrieved 2017-08-07.
  8. ↑ How to Make Everything Ourselves: Open Modular Hardware
  9. ↑ After more than 30 years, grid beam modular construction system comes to market
  10. ↑ Analysis, Design and Construction of Steel Space Frames
  11. ↑ Interlocking bricks used in Nepal
  12. ↑ Bricks that interlock
  13. ↑ Conceptos Plasticos interlocking bricks (i.e. made from plastic waste)
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