A monolithic dome (from Greek mono- and -lithic, meaning "one stone") is a thin-shell 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. Monolithic domes are a form of monolithic architecture.
The igloo may be the earliest form of monolithic dome. While it is constructed of blocks of compressed snow, 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, and the insulation is due to the minimal surface area of a spherical section.
The first modern monolithic dome structure was built in Provo, Utah, by architect Lee C. Knell, and opened in 1963 as an ice skating rink. Called Turtle Reams after its 1967 conversion into a general store by new owner Paul Ream, the building stood until it was demolished in 2006 for new construction.
Turtle Reams was built by first creating a mound of dirt in the desired shape of the shell, an ellipsoidal section 240feet long, 160feet wide and 40feet high. The mound was then covered in a grid of rebar, to provide strength, and a layer of concrete approximately 4inches 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.
Today, monolithic domes are used in a variety of residential, commercial and industrial projects. Because of the strength, durability and economics, they are used to store large amounts of various commodities in the cement, fertilizer, agricultural, power and mining industries. Due to their structural integrity, they are used as the containment buildings at some nuclear power plants. Forms have been made using nearly every common structural material, including air-pressure-supported fabric.
Modern construction differs significantly from the original concrete-over-dirt method. The current methods were developed by three brothers from Idaho: David, Barry, and Randy South. The first dome built using these method was constructed in April 1976 in Shelley, Idaho:
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.
The dome, when finished, is earthquake, tornado and hurricane resistant (the US Federal Emergency Management Agency 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:
The demolition of Reams’ Turtle also demonstrated the durability of the monolithic dome structure. A 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.
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 thermal mass inside the building, reducing interior temperature fluctuations far more than the traditional home's insulation inside of a brick or stone veneer.
While the monolithic dome has numerous demonstrated engineering advantages, there are also some disadvantages, both engineering and social.
Social disadvantages of monolithic domes are to a large degree shared by geodesic domes, due to the similar shape and unorthodox construction. These disadvantages are:
The largest monolithic dome in the world is the home of Faith Chapel Christian Center in Birmingham, Alabama, which is 72feet tall, and 280feet in diameter.[1] Inside is a floor area of 74500square feet in two levels.[2]
Some communities in the United States have chosen to use monolithic dome technology in the construction of new schools.[3]
A residential house, the monolithic "Dome of a Home" on Ariola Drive in Pensacola Beach, Florida, has experienced several hurricanes since it was built in 2003.[4]