Modular building
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Modular buildings and modular homes are sectional prefabricated buildings or houses that consist of multiple modules or sections which are manufactured in a remote facility and then delivered to their intended site of use. The modules are assembled into a single residential building using either a crane or trucks.
Modular buildings are considerably different from mobile homes. Off-frame modular dwellings differ from mobile homes largely in their absence of axles or a frame, meaning that they are typically transported to their site by means of flat-bed trucks; however, some modular dwellings are built on a steel frame (on-frame modular), which can be used for transportation to the site. Many modular homes are of multi-level design, and are often set in place using a crane.
Uses
Modular buildings have a wide variety of uses. They will either be used for long-term temporary or permanent facilities. Such uses include construction camps, schools and classrooms, civilian and military housing needs, and industrial facilities. Modular buildings are a perfect solution in remote and rural areas where conventional construction may not be reasonable or even possible. Other uses have also been found for modular buildings including churches, health care facilities, sales and retail offices, fast food restaurants and cruise ship construction.
Construction process
Modular components are typically constructed within a large indoor facility on assembly lines much like Henry Ford originally instituted with his automobile company. Such facilities use an assembly line track to move the modules from one workstation to the next. Independent building inspectors are on site to supervise the construction and ensure that all building codes are adhered to during assembly.
The modules that will combine to form the house are assembled off-site in a factory. These modules can take one to three months to be constructed but often take as little as 10 days actually to construct when they are first started. Then they are transported to the building site where a crane is brought in to assemble the modules together. The placement of the modules together generally takes several hours or days. Once assembled, modular buildings are essentially indistinguishable from typical site-built homes. While mobile manufactured buildings often decrease in value over time, a well-built modular should have the same longevity as its site-built counterpart, increasing in value over time.
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Bulk materials
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Walls attached to floor
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Ceiling drywalled in spray booth
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Roof set in place
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Roof shingled and siding installed
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Ready for delivery to site
Advantages
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Modular buildings are very affordable because of the factory construction of these buildings. They are very cost effective compared to conventional construction. These units are typically constructed in an enclosed facility, therefore weather is not a factor in the construction time line. Material delivery fees are also out of the equation because an ample amount of material will always be available at the facility, as opposed to being delivered in limited quantities to the job site, nearly eliminating construction delays, and theft of building materials from the site.
Such dwellings are often priced lower than their site-built counterparts and are typically more cost-effective to builders and consumers. These new homes can be constructed in less time than it takes to build a home "on-site".[1] Manufacturers cite the following reasons for the typically lower cost/price of these dwellings:
- 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%.
- Indoor construction. Assembly is independent of weather which increases work efficiency and avoids damaged building material.
- Favorable pricing from suppliers. Large-scale manufacturers can effectively bargain with suppliers for discounts on materials.
- Ability to service remote locations. Particularly in countries 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. Modular homes can be built in major towns and sold to regional areas.[2]
- 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.[3]
- More environmentally friendly construction process - modular construction generates less materials waste and less site disturbances than comparable site built structures.
Market acceptance
Some home buyers and some lending institutions resist consideration of modular homes as equivalent in value to site-built homes. 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 & Australia modular homes have become quite accepted in regional areas however are not commonly built in major cities. Some modular building manufacturers have begun to refer to modular buildings as “off-site construction” to combat the negative image of modular which is due to portables or trailer stereotypes. Recent innovations allow modular buildings to be indistinguishable from site built structures.
Modular homes vs. mobile homes
Differences include the building codes that govern the construction, types of material used and how they are appraised by banks for lending purposes. The codes that govern the construction of modular homes are the exact same codes that govern the construction of any site constructed home. In the United States, all modular homes are constructed according the International Building Code (IBC), IRC, BOCA or the code that has been adopted by the local jurisdiction.
Mobile homes (manufactured homes) are constructed according to the HUD Code and are generally considered lesser quality. The materials are the same as site constructed homes. Wood frame floors, walls and roof is the most typical. Some modulars even included brick or stone exteriors, granite counters and steeply pitched roofs. All modulars are designed to sit on a perimeter foundation or basement. Mobile homes are constructed with a steel chassis that is integral to the integrity of the floor system. Mobile homes often require special lenders. Most companies have standard plans. However, all modular buildings can be custom built to a clients specifications. Today's designs include multi-story units, multi-family units and entire apartment complexes. The negative stereotype commonly associated with mobile homes and has prompted some manufacturers to start using the term Off-Site Construction.
Standards and zoning considerations
Typically, modular dwellings are built to local state or council code, so dwellings built in a given manufacturing facility will have differing construction standards depending on the final destination of the modules [4]. Steel and/or wood framing are common options for building a modular homes. Modular home designs can be customized for local zoning codes. For example, homes built for final assembly in a hurricane prone area can have additional bracing built-in to meet local building codes.
Some US courts have ruled that zoning restrictions applicable to mobile homes do not apply to modular homes since modular homes are often assembled with a permanent foundation. Additionally, in the US, the Uniform Standards of Professional Appraisal Practice allow site-built homes to be used as comparators to modular homes in real estate appraisal; thus, modular homes can in some cities and counties (depending on local ordinances) be evaluated the same way as traditionally 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. [5]
Building strength
According to manufacturers, modular homes are generally designed to be initially stronger than traditional homes by, for example, replacing nails with screws and adding glue to joints. This is supposed to help the modules maintain their structural integrity as they are transported on trucks to the construction site. Despite manufacturer claims that the modular home is initially built to be stronger than a traditional home, it is difficult to predict the final building strength since it needs to endure transportation stresses that traditional homes never experience.
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.[6]
Typically, a modular home contains about 10% to 20% more lumber compared to traditional stick-built homes. This is because modules need to be transported to the job site and the additional lumber helps keep them stable.
Surfaces and finishes
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 that a modular structure can be built to depends on jurisdiction but a number of countries, especially in Asia, allow them to be built to 24 floors and possibly even more.
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 apart of – separate from – applied in the field after the basic installation is completed.
See also
References
- ^ "Modular homes make sense". Retrieved 2007-07-12.
- ^ "Mining boom housing shortage". Retrieved 2007-10-21.
- ^ "Modular and Green". Retrieved 2006-09-15.
- ^ "Australian Government modular home regulations". Retrieved 2007-10-21.
- ^ "Building Codes for Modular Homes". Retrieved 2007-07-12.
- ^ http://www.fema.gov/library/viewRecord.do?id=2765
External links
- Modular Building Systems Association – National trade association representing the legislative and regulatory interests of the modular housing industry
- National Association of Home Builders (United States)
- ModularCenter.com Modular Homes National network of modular home builders & manufacturers along with general information on modular homes and a large database of modular home plans
- Modular Building Institute – International trade association representing non residential modular construction professionals
- Modular Homes Network