Modular building

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Two-story modular dwelling

Modular buildings and modular homes are sectional prefabricated buildings, or houses, that consist of multiple sections called modules. "Modular" is a method of construction differing from other methods (e.g. "stick-built" and other methods such as off-site construction). The modules are six sided boxes constructed in a remote facility, then delivered to their intended site of use. Using a crane, the modules are set onto the building's foundation and joined together to make a single building. The modules can be placed side-by-side, end-to-end, or stacked, allowing a wide variety of configurations and styles in the building layout.

Modular buildings, also called prefabricated buildings, differ from mobile homes, which are also called manufactured homes, in two ways. First, modular homes do not have axles or a frame, meaning that they are typically transported to their site by means of flat-bed trucks. Secondly, modular buildings must conform to all local building codes for their proposed use, while mobile homes, made in the United States, are required to conform to federal codes governed by HUD (U.S. Department of Housing and Urban Development). There are some residential modular buildings that are built on a steel frame (referred to as on-frame modular) that do meet local building codes and are considered modular homes, rather than mobile homes. [1]

Uses[edit]

Modular home in Sutton, Alaska

Modular buildings may be used for long-term, temporary or permanent facilities, such as construction camps, schools and classrooms, civilian and military housing, and industrial facilities. Modular buildings are used in remote and rural areas where conventional construction may not be reasonable or possible, for example, the Halley VI accommodation pods used for a BAS Antarctic expedition.[2] Other uses have included churches, health care facilities, sales and retail offices, fast food restaurants and cruise ship construction.

Construction process[edit]

Modular components are typically constructed indoors on assembly lines. Independent building inspectors are on site to supervise the construction and ensure that the company adheres to all building codes during assembly.[citation needed] Modules' construction may take as little as ten days but more often one to three months. Completed modules are transported to the building site and assembled by a crane. Placement of the modules may take from several hours to several days. Once assembled, modular buildings are essentially indistinguishable from typical site-built structures.[citation needed] While mobile manufactured buildings often decrease in value over time, a well-built modular building should retain value similarly to site-built structures.[citation needed]

Manufacturing considerations[edit]

The entire process of modular construction must place great importance on the design stage. This is where practices such as Design for Manufacture and Assembly (DfMA) are used to ensure that assembly tolerances are controlled throughout manufacture and assembly on site. It is vital that there is enough allowance in the design to allow the assembly to take up any "slack" or miss-alignment of components. The use of advanced CAD systems and manufacturing control systems are important for modular construction to be successful. This is quite unlike on-site construction where the tradesman can often make the part to suit any particular installation.

Advantages[edit]

Modular buildings are often priced lower than their site-built counterparts, for a variety of reasons.[3]

  • Speed of construction/faster return on investment. Modular construction allows for the building and the site work to be completed simultaneously, reducing the overall completion schedule by as much as 50%.[citation needed]
  • Indoor construction. Assembly is independent of weather, which increases work efficiency and avoids damaged building material.[citation needed]
  • Favorable pricing from suppliers. Large-scale manufacturers can effectively bargain with suppliers for discounts on materials.[citation needed]
  • Ability to service remote locations. Particularly in countries in which potential markets may be located far from industrial centers, such as Australia, there can be much higher costs to build a site-built house in a remote area or an area experiencing a construction boom such as mining towns.[citation needed] Modular homes can be built in major towns and sold to regional areas.
  • Low waste. With the same plans being constantly built, the manufacturer has records of exactly what quantity of materials are needed for a given job. While waste from a site-built dwelling may typically fill several large dumpsters, construction of a modular dwelling generates much less waste.[citation needed]
  • Environmentally friendly construction process. Modular construction reduces waste and site disturbance compared to site-built structures.[citation needed]
  • Environmental benefits for used modular buildings. Modular buildings contain 100% reusable components.[citation needed] This means you have the ability to take the building down and relocate it.[citation needed] Should a company's needs change, the modular room can be moved and they never lose their original investment. Pre-owned modular buildings in particular are recognised by the UK Government as being extremely environmentally friendly compared with an equivalent new manufactured building.[citation needed] When a used modular building is relocated with minimal alterations, then the amount of energy used is approximately 3% of the energy that is required to manufacture a new equivalent modular building when minimal alterations are made.[citation needed] The reason for this is that the embodied energy contained within a modular building is transportable and is locked within the fabric of the building.[citation needed]
  • Flexibility. Conventional buildings can be difficult to extend, however with a modular building you can simply add sections, or even entire floors.[citation needed]
  • Healthier. Because modular homes are built in a factory, the materials are stored indoors in a controlled environment, eliminating the risk of mold, mildew, rust, and sun damage that can often lead to human respiratory problems.[citation needed] Traditional site-built homes are always at risk from these threats.[citation needed]

Disadvantages[edit]

Whilst there are many advantages to all forms of modular buildings, there can be limitations also.

  • Volumetric: Transporting the completed modular building sections take up a lot of space. This is balanced with the speed of construction once arrived on site.[citation needed]
  • Flexibility: Due to transport and sometimes manufacturing restrictions, module size can be limited, affecting room sizes. Panelised forms and flat pack versions can provide easier shipment, and most manufacturers have flexibility in their processes to cope with the majority of size requirements.

Market acceptance[edit]

Raines Court is a multi-story modular housing block in Stoke Newington, London, one of the first two residential buildings in Britain of this type. (December 2005)

Some home buyers and some lending institutions resist consideration of modular homes as equivalent in value to site-built homes.[citation needed] While the homes themselves may be of equivalent quality, entrenched zoning regulations and psychological marketplace factors may create hurdles for buyers or builders of modular homes and should be considered as part of the decision-making process when exploring this type of home as a living and/or investment option. In the UK and Australia, modular homes have become accepted in some regional areas; however, they are not commonly built in major cities. Recent innovations allow modular buildings to be indistinguishable from site-built structures.[citation needed] Surveys have shown that individuals can rarely tell the difference between a modular home and a site-built home.[citation needed]

Modular homes vs. mobile homes[edit]

Differences include the building codes that govern the construction, types of material used and how they are appraised by banks for lending purposes.[citation needed] The codes that govern the construction of modular homes are exactly the same codes that govern the construction of site-constructed homes.[citation needed] In the United States, all modular homes are constructed according to the International Building Code (IBC), IRC, BOCA or the code that has been adopted by the local jurisdiction.[citation needed]

Recognizing a mobile or manufactured home[edit]

A mobile home should have a small metal tag on the outside of each section. If you cannot locate a tag, you should be able to find details about the home in the electrical panel box. This tag should also reveal a manufacturing date.[4] Modular homes do not have metal tags on the outside but will have a dataplate installed inside the home, usually under the kitchen sink or in a closet. The dataplate will provide information such as the manufacturer, third party inspection agency, appliance information, and manufacture date.

Materials[edit]

The materials used in modular homes are the same as site constructed homes.[citation needed] Wood-frame floors, walls and roof are the most typical. Some modular homes include brick or stone exteriors, granite counters and steeply pitched roofs. All modulars are designed to sit on a perimeter foundation or basement.[citation needed] In contrast, mobile homes are constructed with a steel chassis that is integral to the integrity of the floor system. Mobile homes often require special lenders.[citation needed] Most companies have standard plans. However, all modular buildings can be custom built to a client's specifications.[citation needed] Today's designs include multi-story units, multi-family units and entire apartment complexes. The negative stereotype commonly associated with mobile homes has prompted some manufacturers to start using the term "off-site construction."[5]

Standards and zoning considerations[edit]

Typically, modular dwellings are built to local, state or council code, resulting in dwellings from a given manufacturing facility having differing construction standards depending on the final destination of the modules.[6] For example, homes built for final assembly in a hurricane-prone area may include additional bracing to meet local building codes. Steel and/or wood framing are common options for building a modular home.

Some US courts have ruled that zoning restrictions applicable to mobile homes do not apply to modular homes since modular homes are designed to have a permanent foundation.[citation needed] Additionally, in the US, valuation differences between modular homes and site-built homes are often negligible in real estate appraisal practice; modular homes can, in some market areas, (depending on local appraisal practices per Uniform Standards of Professional Appraisal Practice) be evaluated the same way as site-built dwellings of similar quality. In Australia, manufactured home parks are governed by additional legislation that does not apply to permanent modular homes. Possible developments in equivalence between modular and site-built housing types for the purposes of real estate appraisals, financing and zoning may increase the sales of modular homes over time.[7]

Building strength[edit]

Modular homes are designed to be stronger than traditional homes by, for example, replacing nails with screws, adding glue to joints, and using 10-20% more lumber than conventional housing.[citation needed] This is to help the modules maintain their structural integrity as they are transported on trucks to the construction site; however, it is difficult to predict the final building strength since the modules need to endure transportation stresses that traditional homes never experience.[citation needed]

When FEMA studied the destruction wrought by Hurricane Andrew in Dade County Florida, they concluded that modular and masonry homes fared best compared to other construction.[8]

CE marking[edit]

The CE mark is a construction norm that guarantees the user of mechanical resistance and strength of the structure. It is a label given by European community empowered authorities for end-to-end process mastering and traceability.[citation needed]

All manufacturing operations are being monitored and recorded:

  • Suppliers have to be known and certified,
  • Raw materials and goods being sourced are to be recorded by batch used,
  • Elementary products are recorded and their quality is monitored,
  • Assembly quality is managed and assessed on a step by step basis,
  • When a modular unit is finished, a whole set of tests are performed and if quality standards are met, a unique number and EC stamp is attached to and on the unit.

This ID and all the details are recorded in a database, At any time, the producer has to be able to answer and provide all the information from each step of the production of a single unit, The EC certification guaranties standards in terms of durability, resistance against wind and earthquakes.[citation needed]

Surfaces and finishes[edit]

Modular buildings can be assembled on top of multiple foundation surfaces, such as a crawl space, stilts (for areas that are prone to flooding), full basements or standard slab at grade. They can also be built to multi-story heights. Motels and other multi-family structures have been built using modular construction techniques. The height to which a modular structure can be built depends on jurisdiction, but a number of countries, especially in Asia, allow them to be built to 24 floors or more.[citation needed]

Exterior wall surfaces can be finalized in the plant production process or in the case of brick/stone veneers, field applications may be the builders' choice. Roof systems also can be applied in the field after the basic installation is completed.

U.S. regional differences with modular construction[edit]

Weather, population density, geographical distances, and local housing architecture play a role in the use of modular construction for home building. Because modular construction is so adaptable, it has begun to permeate every region of the U.S.[citation needed]

Northeast[edit]

The northeast is populated with factories that can combine modular housing design with other construction methods such as panelization and SIPs. Modules are typically limited to 16' width and up to 70' lengths because of the narrow road structure and densely populated areas of the region.[citation needed] Other limitations are placed on transportation to locations such as Connecticut, Cape Cod, and Long Island.[citation needed]

Mid-Atlantic[edit]

The Mid-Atlantic region is similar to the northeast, in terms of building design and transport restriction to modules to a width of not more than 16'.[citation needed]

Southeast[edit]

Manufacturers in the Southeast often limit their ability to customize homes and focus on very traditional single story floor plans.[citation needed] Much of the south is in coastal and high wind areas; modular construction may prove appealing in this area as it is already inherently stronger as it must be built for transport and craned installation, therefore offering wind resistance as good or higher than site-built construction.[citation needed]

Central Plains[edit]

The central plains states typically are made up of farming and rural communities. Ranch homes are the mainstay of the region. Prone to strong storms and tornado conditions, modular construction offers the ability to better withstand these storm patterns than its site built counterpart.[citation needed] The inter-module attachments that must be made when assembling a modular home on a foundation offer an inherently stronger home than site built construction can offer.[citation needed] Interior finishes on both the walls and ceilings are typically textured. Corners on interior walls are typically rounded and finish trim around windows is optional. Because of the wider road and lower population density, modules can be as wide as 20' and as long as 90'. The ability to provide larger modules reduces the amount of modules needed to complete a home.

Rockies[edit]

Home design in this area ranges from Chalet style homes to log cabin style homes. Manufacturers in the region therefore provide a number of styles of homes. Capability varies from factory to factory as well as the ability to do complete customization of floor plans. Transportation is limited mostly to 16' wide modules to travel the roads of the area.[citation needed]

West Coast[edit]

The high cost of living in coastal areas, and especially California, may provide modular construction an edge due to its lower cost.[citation needed] Extreme building regulation and environmental requirements can delay the start of residential construction.[citation needed] Several factories specialize in environmentally responsible construction by following green construction standards and offering zero energy homes.[citation needed]

Living in coastal areas also mean that the modular home structure should be strong enough to withstand winds with high velocity. Modular homes, built correctly, have such kind of resistant to stand high wind velocity without any damage issues.[citation needed]

See also[edit]

References[edit]

External links[edit]