Mechanical Floor

A mechanical floor or mechanical level is a floor of a high-rise building that is dedicated to mechanics and electronics equipment. "Mechanical" is the most commonly-used term, but words such as utility, technical, service, and plant are also used. They are present in all tall buildings, however this article focuses on the cases of the best-known, World's tallest structures#Tallest buildings skyscrapers with significant structural engineering, mechanical engineering and aesthetics concerns.

While most lowrise buildings have utility rooms, typically in the basement, tall buildings require dedicated floors throughout the structure for this purpose, for a variety of reasons discussed below. Because they use up valuable floor area (just like elevator shafts), engineers try to minimize the number of mechanical floors while allowing for sufficient redundancy in the services they provide. As a rule of thumb, skyscrapers require a mechanical floor for every 10 tenant floors (10%) although this percentage can vary widely (see #Examples below). In some buildings they are clustered in groups that divide the building into blocks, in others they are spread evenly through the structure, in others still they are mostly concentrated at the top.

Mechanical floors are generally counted in the building's floor numbering (this is required by some building codes) but are accessed only by service elevators. In some legislations they have been excluded from maximum floor area calculations, leading to significant increases in building sizes; this is the case in New York City (greadgridlock.net).

Structural concerns

Skyscrapers have narrow building cores that require stabilization to prevent collapse. Typically this is accomplished by joining the core to the external supercolumns at regular intervals using outrigger trusses. The triangular shape of the struts precludes the laying of tenant floors, so these sections house mechanical floors instead, typically in groups of two. Additional stabilizer elements such as tuned mass dampers also require mechanical floors to contain or service them.

This layout is usually reflected in the internal elevator zoning. Since all elevators require machine rooms above the last floor they service, mechanical floors are often used to divide shafts that are stacked on top of each other to save space. A transfer level or skylobby is sometimes placed just above those floors.

Elevators that reach the top tenant floor also require overhead machine rooms; those are sometimes put into full-size mechanical floors but most often into a mechanical penthouse, will can also contain communications gear and window-washing equipment. On most building designs this is a simple "box" on the roof, on others it is concealed inside a decorative spire. A consequence of this is that if the topmost mechanical floors are counted in the total, there can be no such thing as a true "top-floor office" in a skyscraper.

Mechanical concerns

Besides structural support and elevator management, the primary purpose of mechanical floors is HVAC, and other services. They contain electrical generators, chiller plants, water pumps, and so on.

In particular, the problem of bringing and keeping water on the upper floors is an important constraint in the design of skyscrapers. Water is necessary for tenant use, air conditioning, equipment cooling, and basic firefighting through fire sprinklers (especially important since ground-based firefighting equipment usually cannot reach higher than a dozen floors or so). It is inefficient, and seldom feasible, for water pumps to send water directly to a height of several hundred meters, so intermediate pumps and water tanks are used. The pumps on each group of mechanical floors acts as a relay to the next one up, while the tanks hold water in reserve for normal and emergency use. Usually the pumps have enough power to bypass a level if the pumps there have failed, and send water two levels up.

Special care must be taken towards fire safety on mechanical floors that contain generators, compressors and elevator machine rooms, since oil is used as either a fuel or lubricant in those elements.

Mechanical floors also contain communication and control systems that service the building and sometimes outbound communications, such as through a large rooftop antenna (electronics) (which is also physically held in place inside the top-floor mechanical levels).

Modern computerized HVAC control systems minimize the problem of equipment distribution among floors, by enabling remote central control.

Aesthetics concerns

Most mechanical floors require external vents or louvers for ventilation and heat rejection along most or all of their perimeter, precluding the use of glass windows. The resulting visible "dark bands" can disrupt the overall facade design especially if it is fully glass-clad. Different architectural styles approach this challenge in different ways.

In the Modern architecture and International style (architecture) styles of the 60s and 70s where form follows function, the vents' presence is not seen as undesirable. Rather it emphasizes the functional layout of the building by dividing it neatly into equal blocks, mirroring the layout of the elevators and offices inside. This can be clearly seen on the World Trade Center twin towers and the Sears Tower.

Conversely, designers of the recent Postmodern architecture-style skyscrapers strive to mask the vents and other mechanical elements in clever and ingenious ways. This is accomplished through such means as complex wall angles (PETRONAS Twin Towers), intricate latticework cladding (Jin Mao Building), or non-glassed sections that appear to be ornament (Taipei 101, roof of Jin Mao Building).

Examples

Here are examples of above-ground mechanical floor layouts for some of the world's tallest buildings. In each case, mechanical penthouses and spires are counted as floors, leading to higher total floor counts than usual.

Taipei 101: Floors 7-8, 17-18, 25-26, 34, 42, 50, 58, 66, 74, 82, 87, 90-91, and 102 in the penthouse (total 17/102, or 17%). The official count of 11 corresponds to the number of groups in the office section. Floors 92-100 contain "communications equipment" and so are not typically counted as mechanical since they do not service the building itself.

World Trade Center Twin Towers: Floors 7-8, 41-42, 75-76, and 108-109 (total 8/110, 7%). It is unclear whether a mechanical penthouse existed as part of the 110th floor or on top of it (yielding respectively 9/110, and 9/111 or 8%). Some sources erroneously mention 12 floors, in groups of 3, due to the height of the vents (actually the ceilings there were higher) and because levels 44 and 78 were skylobby which in many buildings sit directly on top of the mechanical floors. However the twin towers had one One World Trade Center tenants office floor under each skylobby, accessible through escalators.

Sears Tower: Levels 30-31, 48-49, 64-65, 104-108, and 109-110 in the penthouse (total 13/110, 12%).

PETRONAS Twin Towers: Floors 2-7, 38-40, 43, 84, 87-88 (total 13/88, 15%) (New York Times, Elevator World magazine)

Jin Mao Building: Floors 51-52, and 89-93 in the penthouse (total 7/93, 7.5%) (SkyscraperPage)

External Links

Definitions of building floors on Emporis
Case study for Hong Kong's Central Plaza by the Department of Architecture of Hong Kong University, Energy Features section


Home Articles Construction Tools Woodworking Store Tools Furniture Bathroom Flooring	Mechanical Floor A mechanical floor or mechanical level is a floor of a high-rise building that is dedicated to mechanics and electronics equipment. "Mechanical" is the most commonly-used term, but words such as utility, technical, service, and plant are also used. They are present in all tall buildings, however this article focuses on the cases of the best-known, World's tallest structures#Tallest buildings skyscrapers with significant structural engineering, mechanical engineering and aesthetics concerns. While most lowrise buildings have utility rooms, typically in the basement, tall buildings require dedicated floors throughout the structure for this purpose, for a variety of reasons discussed below. Because they use up valuable floor area (just like elevator shafts), engineers try to minimize the number of mechanical floors while allowing for sufficient redundancy in the services they provide. As a rule of thumb, skyscrapers require a mechanical floor for every 10 tenant floors (10%) although this percentage can vary widely (see #Examples below). In some buildings they are clustered in groups that divide the building into blocks, in others they are spread evenly through the structure, in others still they are mostly concentrated at the top. Mechanical floors are generally counted in the building's floor numbering (this is required by some building codes) but are accessed only by service elevators. In some legislations they have been excluded from maximum floor area calculations, leading to significant increases in building sizes; this is the case in New York City (greadgridlock.net). Structural concerns Skyscrapers have narrow building cores that require stabilization to prevent collapse. Typically this is accomplished by joining the core to the external supercolumns at regular intervals using outrigger trusses. The triangular shape of the struts precludes the laying of tenant floors, so these sections house mechanical floors instead, typically in groups of two. Additional stabilizer elements such as tuned mass dampers also require mechanical floors to contain or service them. This layout is usually reflected in the internal elevator zoning. Since all elevators require machine rooms above the last floor they service, mechanical floors are often used to divide shafts that are stacked on top of each other to save space. A transfer level or skylobby is sometimes placed just above those floors. Elevators that reach the top tenant floor also require overhead machine rooms; those are sometimes put into full-size mechanical floors but most often into a mechanical penthouse, will can also contain communications gear and window-washing equipment. On most building designs this is a simple "box" on the roof, on others it is concealed inside a decorative spire. A consequence of this is that if the topmost mechanical floors are counted in the total, there can be no such thing as a true "top-floor office" in a skyscraper. Mechanical concerns Besides structural support and elevator management, the primary purpose of mechanical floors is HVAC, and other services. They contain electrical generators, chiller plants, water pumps, and so on. In particular, the problem of bringing and keeping water on the upper floors is an important constraint in the design of skyscrapers. Water is necessary for tenant use, air conditioning, equipment cooling, and basic firefighting through fire sprinklers (especially important since ground-based firefighting equipment usually cannot reach higher than a dozen floors or so). It is inefficient, and seldom feasible, for water pumps to send water directly to a height of several hundred meters, so intermediate pumps and water tanks are used. The pumps on each group of mechanical floors acts as a relay to the next one up, while the tanks hold water in reserve for normal and emergency use. Usually the pumps have enough power to bypass a level if the pumps there have failed, and send water two levels up. Special care must be taken towards fire safety on mechanical floors that contain generators, compressors and elevator machine rooms, since oil is used as either a fuel or lubricant in those elements. Mechanical floors also contain communication and control systems that service the building and sometimes outbound communications, such as through a large rooftop antenna (electronics) (which is also physically held in place inside the top-floor mechanical levels). Modern computerized HVAC control systems minimize the problem of equipment distribution among floors, by enabling remote central control. Aesthetics concerns Most mechanical floors require external vents or louvers for ventilation and heat rejection along most or all of their perimeter, precluding the use of glass windows. The resulting visible "dark bands" can disrupt the overall facade design especially if it is fully glass-clad. Different architectural styles approach this challenge in different ways. In the Modern architecture and International style (architecture) styles of the 60s and 70s where form follows function, the vents' presence is not seen as undesirable. Rather it emphasizes the functional layout of the building by dividing it neatly into equal blocks, mirroring the layout of the elevators and offices inside. This can be clearly seen on the World Trade Center twin towers and the Sears Tower. Conversely, designers of the recent Postmodern architecture-style skyscrapers strive to mask the vents and other mechanical elements in clever and ingenious ways. This is accomplished through such means as complex wall angles (PETRONAS Twin Towers), intricate latticework cladding (Jin Mao Building), or non-glassed sections that appear to be ornament (Taipei 101, roof of Jin Mao Building). Examples Here are examples of above-ground mechanical floor layouts for some of the world's tallest buildings. In each case, mechanical penthouses and spires are counted as floors, leading to higher total floor counts than usual. Taipei 101: Floors 7-8, 17-18, 25-26, 34, 42, 50, 58, 66, 74, 82, 87, 90-91, and 102 in the penthouse (total 17/102, or 17%). The official count of 11 corresponds to the number of groups in the office section. Floors 92-100 contain "communications equipment" and so are not typically counted as mechanical since they do not service the building itself. World Trade Center Twin Towers: Floors 7-8, 41-42, 75-76, and 108-109 (total 8/110, 7%). It is unclear whether a mechanical penthouse existed as part of the 110th floor or on top of it (yielding respectively 9/110, and 9/111 or 8%). Some sources erroneously mention 12 floors, in groups of 3, due to the height of the vents (actually the ceilings there were higher) and because levels 44 and 78 were skylobby which in many buildings sit directly on top of the mechanical floors. However the twin towers had one One World Trade Center tenants office floor under each skylobby, accessible through escalators. Sears Tower: Levels 30-31, 48-49, 64-65, 104-108, and 109-110 in the penthouse (total 13/110, 12%). PETRONAS Twin Towers: Floors 2-7, 38-40, 43, 84, 87-88 (total 13/88, 15%) (New York Times, Elevator World magazine) Jin Mao Building: Floors 51-52, and 89-93 in the penthouse (total 7/93, 7.5%) (SkyscraperPage) External Links Definitions of building floors on Emporis Case study for Hong Kong's Central Plaza by the Department of Architecture of Hong Kong University, Energy Features section
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