Monolithic Dome Movement
April 30, 2003
by
David B. South
 David B. South, President of the Monolithic Dome Institute |
Monolithic Dome movement was discussed as a "problem" at the 2003 conference. We want to share our observations of this issue as experienced dome builders. First, we eliminate from our findings any non-insulated concrete domes and thin shells subject to wide temperature swings. These structures do have or can have substantial movement as the temperatures within them change.
The following information refers to Monolithic Domes used for houses, schools, churches, and other small to midsize facilities. The thermal dynamics of the insulated Monolithic Domes are such that they do not change enough in temperature to cause them to change size and shape. They are thermally stable. I have never seen a Monolithic Dome home move enough to be measured. I have seen sheet rock damaged, door frames separate, and cracks in sheetrock appear, but upon investigation we always find that the Monolithic Dome remained firm, but interior walls or floors have moved.
A Monolithic Dome is virtually immune to earth movement whether from earthquake or swelling soils. The floors must be protected. For small structures such as houses, the floors and foundations work as a unit. The dome is attached with the rebar to the floor/footing. Building domes this way allows the building to float and move as a unit. Water and sewer lines need to have some room for movement as the house may move as a single piece.
For bigger domes, such as the gymnasiums, proper attention must be given to soil preparation and compacting. Attention must be given to the earth below the floor to insure it will not have changes in the moisture content. Moisture contributes to swelling under the floor. If the floor does not move up or down it will eliminate interior wall movement. At the gym in Pattonsburg, Missouri, the ground was not properly compacted under the center part of the dome. Consequently the interior walls (built of concrete blocks) are sinking away from the dome. This is not a problem caused by the dome, but a problem created due to inadequate ground preparation. Erroneously the damage had been attributed to the dome movement. The inspection quickly identified the stability of the dome and the problems due to the under-floor compaction.
My Monolithic Dome home is now about nine years old. I checked it out very carefully just before the conference. There is one place where there is a sheet rock corner crack about 3 feet long and the thickness of a pencil line. It is in an area where the conventional ceiling above it may be moving. None of the walls that go to the dome show any sign of movement. The visiting architect I had with me commented that the shrinking of a wood stud would create more movement than what we observed. This is true of my home in Idaho (Cliff Dome) as well Charca Casa.
Keep in mind -- never put a steel beam between the floor and the dome as there might be some movement. Do not use concrete block directly under the dome without a bit of expansion space. Steel studs and sheet rock are not a problem. It is a good idea to caulk the final 1/4 or 1/8 inch between the sheetrock and the dome wall.
In a nutshell -- the Monolithic Dome's thermal dynamics prevent any structural movement. If kept at room temperatures, shell movement of a Monolithic Dome is a not a problem.
Related Articles:
- Soil Bearing Conditions
- Pattonsburg Monolithic Dome School
- Charca Casa -- Italy, Texas
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