A monolithic dome is a structure cast in a one-piece form. The form may be permanent or temporary and may or may not remain part of the finished structure.

Forms have been made using nearly every common structural material including air pressure supported fabric.

Monolithic domes are a form of monolithic architecture

Monolithic architecture

Monolithic architecture is a style of construction in which a building is carved, cast or excavated from a single piece of material. The most basic form of monolithic architecture is the monolith, such as the monolithic churches of Lalibela, Ethiopia or the Pancha Rathas in India.Buildings with a...

.

History

The earliest form of monolithic dome structure could be considered to be the igloo

Igloo

An igloo or snowhouse is a type of shelter built of snow, originally built by the Inuit....

. While it is constructed of blocks of compressed snow

Snow

Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...

, these blocks melt and re-freeze to form a strong, homogeneous structure. The dome-like shape of the igloo exhibits the two major advantages of a dome-shaped structure: great strength, and good insulation. The strength is due to the natural strength of the arch

Arch

An arch is a structure that spans a space and supports a load. Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.-Technical aspects:The...

, and the insulation is due to the minimal surface area of a spherical

Sphere

A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...

 section.

The first modern monolithic dome structure was built in Provo, Utah

Provo, Utah

Provo is the third largest city in the U.S. state of Utah, located about south of Salt Lake City along the Wasatch Front. Provo is the county seat of Utah County and lies between the cities of Orem to the north and Springville to the south...

 and opened in 1963 as an ice skating

Ice skating

Ice skating is moving on ice by using ice skates. It can be done for a variety of reasons, including leisure, traveling, and various sports. Ice skating occurs both on specially prepared indoor and outdoor tracks, as well as on naturally occurring bodies of frozen water, such as lakes and...

 rink. Called Ream's Turtle after its 1967 conversion into a general store

General store

A general store, general merchandise store, or village shop is a rural or small town store that carries a general line of merchandise. It carries a broad selection of merchandise, sometimes in a small space, where people from the town and surrounding rural areas come to purchase all their general...

 by new owner Paul Ream, the building stood until it was demolished in 2006 for new construction.

Ream's Turtle was built by first creating a mound of dirt in the desired shape of the shell, an ellipsoidal section 240 feet (73.2 m) long, 160 feet (48.8 m) wide and 40 feet (12.2 m) high. The mound was then covered in a grid of rebar

Rebar

A rebar , also known as reinforcing steel, reinforcement steel, rerod, or a deformed bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression...

, to provide strength, and a layer of concrete approximately 4 inches (101.6 mm) thick. After the concrete was cured, the dirt was excavated through the doorways, leaving the roof standing in its place. The floor was then poured to finish the structure.

Current construction methods

Modern construction differs significantly from the original concrete-over-dirt method. The current methods were developed by three brothers from Idaho: Barry, Randy, and David South. The first dome built using these method was constructed in Shelley, Idaho

Shelley, Idaho

Shelley is a city in Bingham County, Idaho, United States. The population was 3,813 at the 2000 census. The mascot for the city's high school is "King Russet", a russet-burbank potato that wears a crown, robe and scepter....

:

• A reinforced concrete foundation, or "ring beam", is constructed, defining the shape of the base of the structure.
• The fabric form, or air form, is attached to the foundation and inflated with an air blower. The air form contains an airlock
  Airlock
  An airlock is a device which permits the passage of people and objects between a pressure vessel and its surroundings while minimizing the change of pressure in the vessel and loss of air from it...
  
   to allow workers to enter the form while it is inflated.
• A layer of polyurethane
  Polyurethane
  A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
  
   foam is sprayed on the interior of the form. (Its purposes are to give rigidity to the air form, secure the rebar in place, provide support for spraying in the concrete mixture, and insulate the final structure.)
• Rebar is attached to the outside layer of foam, using clips that are attached to the foam.
• Several inches of concrete are sprayed over the rebar frame.
• After the concrete has set, the blower is turned off.
• The exposed surface of the air form may be left as is, or a surface treatment such as paint, tile, etc., may be applied. (Proper selection of air form material will ensure prevention from long-term degradation due to ultraviolet radiation.)

In instances where necessity requires economical construction for multiple small and basic dwellings, the dome can be built without insulation and the air form can be removed after completion and re-used to build additional domes.

Durability

The dome, when finished, is earthquake

Earthquake

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

, tornado

Tornado

A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...

 and hurricane resistant (FEMA rates them as "near-absolute protection" from F5 tornadoes and Category 5 Hurricanes). Recently, a number of monolithic domes constructed using MDI techniques have survived major disasters:

• Several monolithic domes in Florida
  Florida
  Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
  
   survived direct hits by Hurricane Katrina
  Hurricane Katrina
  Hurricane Katrina of the 2005 Atlantic hurricane season was a powerful Atlantic hurricane. It is the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall...
  
   in 2005.
• Several monolithic domes were in the path of the 2005 and 2006 wildfire
  Wildfire
  A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
  
  s in Oklahoma
  Oklahoma
  Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
  
   and Texas
  Texas
  Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
  
  , and survived with only slight charring of the exterior foam insulation.
• In 2003, a monolithic dome government building in Iraq
  Iraq
  Iraq ; officially the Republic of Iraq is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert....
  
   survived a direct hit by a 5000 lb (2,268 kg). bomb
  Bomb
  A bomb is any of a range of explosive weapons that only rely on the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy...
  
  . The interior of the structure was totally destroyed, but the dome itself remained standing (see picture).

The demolition of Ream's Turtle also demonstrated the durability of the monolithic dome structure. A wrecking ball

Wrecking ball

A wrecking ball is a heavy steel ball, usually hung from a crane, that is used for demolishing large buildings. It was most common during the 1950s and 1960s. Several wrecking companies claim to have invented the wrecking ball...

 demolished a strip several feet wide around the perimeter of the structure, without a collapse. When a doorway on one side was pulled down, the dome finally tipped over, and collapsed.

Climate control

The monolithic dome, for a number of reasons, is very energy efficient. The spherical sections of the dome offer minimal surface area for the volume they contain, so there is less surface for heat transfer with the outside air. The one piece construction of the monolithic dome also eliminates many of the seams through which air can leak, though this is mitigated to some degree in residential domes by the addition of multiple doors and windows. By placing the insulating foam on the outside of the concrete shell, the concrete acts as a heat sink

Heat sink

A heat sink is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems and the radiator in a car...

 inside the building, reducing interior temperature fluctuations far more than the traditional home's insulation inside of a brick or stone veneer.

Disadvantages

While the monolithic dome has numerous demonstrated engineering advantages, there are also some disadvantages, both engineering and social.

Engineering

• The techniques used in monolithic dome construction are very different from normal construction methods, so only specially trained construction crews are suited for building a dome using the modern techniques.
• The curved surfaces inherent to monolithic dome construction often result in oddly shaped rooms when divided up, which can result in wasted space in narrow corners. There are issues of wasted floor space due to wall curvature and problems fitting furniture, similar to those of Quonset hut
  Quonset hut
  A Quonset hut is a lightweight prefabricated structure of corrugated galvanized steel having a semicircular cross section. The design was based on the Nissen hut developed by the British during World War I...
  
  s. This effect can be minimized by constructing the dome on a stem wall, or by using an airform of such shape as to allow for straight, vertical walls at ground level.
• The monolithic dome's lack of seams may make it too well sealed; dehumidifiers are required in all but the driest climates.

Social

Social disadvantages of monolithic domes are to a large degree shared by geodesic dome

Geodesic dome

A geodesic dome is a spherical or partial-spherical shell structure or lattice shell based on a network of great circles on the surface of a sphere. The geodesics intersect to form triangular elements that have local triangular rigidity and also distribute the stress across the structure. When...

s, due to the similar shape and unorthodox construction. These disadvantages are:

• The radically different appearance of the domes also decreases the appeal for their use as private residences—the standard circular base doesn't fit well on small lots found in many areas, and the strange appearance and design may run afoul of neighborhood building covenants. Depending on the situation, a large variety of variations available from the standard circular shape can avoid some of these problems.
• Building permits may be difficult to obtain if local officials are not familiar with the monolithic dome.
• Resale of a monolithic dome home may be difficult because of its unconventional appearance.

Construction records

The largest monolithic dome in the world is the home of Faith Chapel Christian Center

Faith Chapel Christian Center

Faith Chapel Christian Center is a non-denominational, Christian, megachurch located in Ensley, Alabama. The congregation, though largely African American, also consists of a variety of individuals from various ethnic and socio-economic backgrounds...

 in Birmingham, AL. It seizes the record at 72 feet (21.9 m) tall, and 280 feet (85.3 m) in diameter. Inside is a floor area of 74500 square feet (6,921.3 m²) in two levels.

External links

• Dome Technology
• Monolithic Dome Institute
• Building Monolithic Domes, by Sean Lanham, Architecture Week
• Trinity Dome Construction Log, a first-time homebuilder's experience
• JC Tropical Homes Inc., Caribbean dome homes, also commercial/industrial domes.