Monolithic Domes
What is a Monolithic Dome and why would one want to have
one built?
How are these structures built?
The first step is pouring a concrete ring beam foundation.
This foundation is reinforced with steel re-bar which is laid vertically in the cement and
is later attached to the reinforcing steel in the dome. Some floors can be poured after
the dome is built.
The dome is made of concrete that is seamless and nearly
airtight. To make this dome, an Airform is used. This Airform is like a balloon that is
made out of a nylon scrim fabric that has PVC woven into the fibers. This balloon is then
inflated to the desired size and shape and held in place by concrete anchors. The pressure
within the Airform should not increase once the desired pressure is reached. If it is
increased after the concrete is sprayed, it could cause the concrete to pull away from the
Airform and crack. The Airform holds its shape while the polyurethane foam is sprayed on
the inside and hardens. (To gain access to the inside of the Airform, a double door
airlock is used to prevent the Airform from loosing pressure.) This Airform will remain
even after the dome is finished and acts as a roof membrane. This Airform should not be
removed; it protects from moisture leakage. If the Airform is removed it has to be
replaced with a coating of equal value.
All construction takes place inside the dome. The first
layer to be applied to the inside of the Airform is a polyurethane foam insulation. This
foam is an insulation, protecting the concrete that will be applied freeze/thaw cycles and
insulating the interior of the dome. There is not any other kind of material that can
replace the value of this polyurethane foam layer. This is sprayed on in layers to reach a
3" thickness. There will be no joints or seams thus making the dome nearly airtight.
Hangers are placed in the foam for attachment of the rebar, which is attached to the foam
shell to help give the dome its strength. The rebar is applied in a spider-web shape. The
rebar extends vertically as well as horizontally. Three-eighths inch rebar should be used
and spaced 10 inches on center both ways for small domes.
To create openings, such as the doors and windows,
polyurethane foam and shotcrete is only sprayed around the edge of the opening and rebar
is not placed through those openings.
Once the foam and rebar are in place, five layers of
shotcrete are applied. Shotcrete is concrete that is sprayed using a machine. This
shotcrete is sprayed over the whole inner surface of the dome. Professional services may
be required to apply the shotcrete. The first layer of shotcrete should be 1/8 to 1/4 inch
thick and the second coat is applied as soon as the first layer has dried. It may only
take one hour to dry in hot weather, whereas in cold, it may take all night while applying
heat. After the last layer is applied, a hand trowel can be used to smooth the surface.
After the concrete has set the blower fans are turned off. Construction of the dome itself
takes from 7 to 10 days to complete and curing requires three to four weeks. And, after
the dome is completed, construction takes place inside the structure out of the weather.
At this point the dome is self-supporting.
There are many designs that can be applied to bring about
unique architecture. Units can be overlapped; the shell material can be smoothed or
textured. The outside layer can be completed in any color (2).
Why consider building a Monolithic dome?
"The Monolithic Dome is a structure that distributes
stress throughout the dome shell, as opposed to conventional buildings where external
stress is concentrated at one point. This allows it to carry heavy snow loads and
withstand high winds as well as earthquakes" (1). This also allows for earth berming
or partially burying the home so that it blends into its surrounding landscape. The life
span of a monolithic dome has been conservatively estimated by engineers to be 600 to 900
years and the size range from as small as a horse stall to as big as 550’ in
diameter.
The Monolithic Dome is very energy efficient due to its
shape and materials.
The Airform fabric has an estimated life span of 15 years,
is extremely tough, and is Class A fire rated (1).
"Polyurethane foam has the highest insulative value of
any building insulation…" (1). The amount of heat lost to outside elements is
lowered due to the foam being completely bonded to the outside of the concrete dome. Thus
the inside temperature is easily maintained with minimum energy and costs, which are
generally lowered at least 50% or more) (1).
Shotcrete is an excellent heating and cooling system due to
the fact that it lets in heat or cold in gradually, thus eliminating stress on the heating
and cooling system in extreme temperature conditions. It also is very strong and, with the
combination of the foam, "it creates a waterproof, temperature stable
environment" (1). Because of these factors, the Monolithic Dome works well as an
underground structure.
The Monolithic Dome is one of the strongest buildings.
"A typical building will be damaged when weather forces exceed 50 pounds per square
foot. A hurricane may have forces in the 100-200 pound level, while a tornado exerts 400
pounds or more of force. The basic shell of this dome can withstand forces in excess of
10,000 pounds per square foot. Actual strength will depend on the design utilized"
(2). Monolithic Dome homes in North Carolina have been tested by two hurricanes, Bertha
and Fran. These homes were not bothered even though they went through winds up to 115 mph.
A dome makes a good storage building because it is able to withstand heavy products piled
high with their weight leaning up against the walls.
Monolithic Domes are also "able to withstand
substantial amounts of differential soil settlement. As a result, concrete domes can often
be constructed on sites considered too unstable for traditional silos" (4). The
design strength is such that the dome should withstand strong earthquakes.
"The Monolithic Dome is the best building method to
achieve Nature’s perfect shape. Its advantages have been utilized by individuals and
corporations in 42 states and 16 foreign countries for churches, offices, storage,
schools, theaters, water tanks, supermarkets to name just a few of its applications, and
is the only building approved to store explosives on waterways in the United States. There
have also been 28 grain storage domes erected in the Middle East, as well as the command
center of the Indonesian Air Force Base, which are included in the 400-plus Monolithic
Domes built world-wide" (1)!
"It is very cost effective. The complete shell can be
constructed for $30-35 per square foot. Large shells in excess of 120 feet in diameter
will be in the range of $20-24 per square foot. A completely finished building can be done
for $65-70 per square foot or even less" (2). One man built his three bedroom home
for approximately $50,000. This included putting in a drain field, well and power. His
home measured 40 feet in diameter and 15 feet high at the center.
The majority of work done on a Monolithic Dome is done
inside. Weather does not have much of an affect on building the dome once the Airform is
up and work can be done in a temperature controlled environment.
"The Monolithic Dome is ideal for homes, apartments,
bulk storage, stadiums, schools, hockey rinks, cold storage, motels, aircraft hangars,
recreation centers, and much more. It is the building of choice for the discriminate buyer
looking for a safe, long-lasting, energy-efficient building at a cost that is competitive,
and often less than conventional construction" (3)
Here is an article written on a Monolithic Dome home built
in South Carolina and its ability to stand up under great pressure.
Eye of the Storm
When Hurricane Fran was heading toward Sullivans
Island, SC, in 1996, a television news crew asked to ride out the storm in the only house
not affected by the excavation order, Huiet and Helen Paul’s Monolithic Dome home,
dubbed ‘Eye of the Storm.’
Hurricane Hugo had wiped out the Pauls’ first home on
Sullivans Island in 1989. So their contractor son, George Paul, owner of OmniShell of
Sullivans Island, built his parents a four-level, $600,000 luxury dome. A builder of
Monolithic Dome homes and commercial buildings for the past 19 years, Paul designed his
parents’ new home to blend in with its surroundings. ‘The Eye of the Storm
reflects the curve of the beach, the seashell, the dunes,’ he says.
Eight huge openings, five large enough to drive a car
through, are the most striking feature of the home’s ground level. During a
hurricane, these openings allow the storm surge to rush through, leaving the structure
unharmed. Another advantage of the design is that the curved aerodynamic shape actually
bends wind around the house eliminating pressure buildup. While most homes are designed to
withstand a 100-miles- (160-kilometers-) per-hour wind, Eye of the Storm can easily
withstand winds of 150 miles (241 kilometers) per hour, equivalent to a category five
hurricane.
Eye of the Storm also can easily weather any tornado that
may spin off a hurricane, reports George Paul. He observes that domes can withstand a dead
load pressure of 2,000 pounds per square foot (9 metric tons per square meter), so the 400
pounds per square foot (2 metric tons per square meter) exerted by a tornado are
insignificant in comparison. And, because it is a one-piece solid structure, the interior
construction of Eye of the Storm actually strengthens the roof. The home’s living
quarters, which are levels two, three, and four, hang from the shell.
‘That’s 250 tons holding the roof down,’
says Paul."
Works Cited
Baldwin, J.
a. "Advantages." [http://www.zetatalk.com/shelter/tshlt13i.htm].
b. "Disadvantages." [http://www.zetatalk.com/shelter/tshlt13j.htm].
Burnham II, Walter L.
a. [domes@dmi.net].
"Rochy Mountain Dome Co."/"Benefits of a Monolithic Dome." [http://www.concretedomes.com/benefits.html].
[domes@dmi.net].
"Construction Process of a Monolithic Dome"/"Rocky Mountain Dome Co."
[http://www.concretedomes.com/construction.html].
Carder, Carol. [http://youroffice.ingersoll-rand.com/IR/youroffice/contactus.cfm].
"Compressed Air…One Dome At A Time"/"Ingersoll-Rand." [http://www.ingersollrand.com/compare/jul_aug98/dom_2.htm].
1998.
Domtec International, LLC.
a. [domtec@domtecint.com].
"Construction Process." [http://www.domtec.com/process.html].
1998.
b. [domtec@domtecint.com].
"Dome Storage Advantages." [http://www.domtec.com/advantages.html].
1998.
Dubiosgroup. [duboisre@flash.net].
"Future Dome Corporation." [http://www.duboisgroup.com/Future%20Dome.htm].
Genesis II M Monolithic Domes. [info@genesisiim.com]. "Benefits of Monolithic
Domes." [http://www.genesisiim.com/benefits.htm].
1998.
Kirkwood, Byron. "Shelters." [http://baproducts.com/shelters.htm].
October/November 1996.
Leading Edge International Research Group.
"Alternative Housing." [http://www.trufax.org/menu/house.html].
1996-1999.
Monolithic Dome Institute.
[mail@monolithicdome.com].
"How to Build a Monolithic Dome." [http://www.monolithicdome.com/design/mdconst/mdconst.htm].
1997.
b. [mail@monolithicdome.com].
"Monolithic Marketplace." [http://www.monolithicdome.com/marketplace/scaffold.htm].
1997.
Siniff, Edna. [siniff@northcascades.net].
"Balloon Houses and Monolithic Domes"/"Okanogan Times." [http://www.okanogantimes.com/houses1.htm].
1999.
South, David B.
[mail@monlithicdome.com].
"The EcoShell vs. The Monolithic Dome." [http://www.monolithicdome.com/articles/ecovsmono/index.html].
1997.
b.[mail@monolithicdome.com]."Introducing
The Eco Shell II."
[http://www.monolithicdome.com/design/ecoii/ecoii.htm].
1998.
c. "Monolithic Dome." July/August issue of
"Architectural West." Pp.16, 18-19; 1999.
"Tornado Resistant." [http://www.zetatalk.com/shelter/tshlt13b.htm].
Wilson, Arnold. "Troubled Times: Indestructible."
[http://www.zetatalk.com/shelter/tshlt13a.htm].
Zimmerman, Jonathan. "Many Virtues." [http://www.zetatalk.com/shelter/tshlt13o.htm].
Article taken from "Solar Today Magazine."
An excellent source for information on Monolithic Domes is:
P.O. Box 479
209 Dome Park Pl.
Italy, TX 76651
972-483-7423
972-483-6662
dome@domebuilders.com
Fred J.
Becker, Architect
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