The Dome Does Not Have to Be the Roof
One of the important decisions in the development of the Atlas Construction System was to separate two functions that are often treated as one: the structural dome and the weather-protective roof.
The reinforced concrete dome forms part of the permanent structural shell of the building. But there is no reason for that concrete surface to be directly exposed to years of sun, rain, snow, ice, and temperature changes.
Another approach is to protect the concrete with a waterproof membrane and then cover that membrane with a substantial layer of soil. While the soil provides thermal mass and some insulating effect, soil is not, by itself, a particularly efficient insulation material when compared with purpose-designed insulation products. The additional soil also introduces considerable permanent weight that the structure must support.
Atlas approached the problem differently. Rather than placing a heavy protective layer above the dome, Atlas places a lightweight, ventilated roof above it.
Atlas therefore places a conventional pitched roof above the dome.
This seemingly simple decision provides several advantages.
1. A Protective Roof Above the Structural Dome
The roof creates the building's primary weather-protective layer while the reinforced concrete dome remains beneath it.
Rain and melting snow are carried away in the conventional manner, while the roof covering can be selected according to climate, cost, appearance, and local availability.
The roof structure itself can also use familiar construction materials and methods.
The dome provides the permanent structure. The roof above it provides the first line of protection from the weather.
2. The Space Between Them Is Deliberate
The roof is not placed directly against the concrete dome.
A ventilated space is maintained between the dome and the roof covering, allowing outside air to enter at the lower portions of the roof and escape toward the ridge.
That continuous movement of air helps remove accumulated heat and moisture from beneath the roof covering rather than trapping them against the structure.
This is particularly useful because the two systems can then perform their respective functions independently: the concrete dome provides mass and structural strength below, while the lighter roof assembly manages the exterior environment above.
3. A Replaceable Outer Layer
No exterior roof covering lasts forever.
Shingles, metal roofing, tiles, flashings, and other exposed components eventually require maintenance or replacement. In Atlas, those components remain accessible above the permanent reinforced concrete shell.
That creates an important distinction.
The part of the building exposed to the weather can be repaired or replaced without replacing the primary structure beneath it.
It also means Atlas is not dependent upon one particular roofing material. Different roof coverings can be used as appropriate for the building, climate, architectural appearance, or future developments in roofing technology.
4. Two Systems, Two Different Jobs
The ventilated roof does not replace the dome, and the dome does not need to replace the roof.
Each is allowed to do the job for which it is best suited.
The reinforced concrete dome provides the strength, durability, thermal mass, and distinctive interior form that lie at the heart of Atlas.
Above it, the ventilated roof provides drainage, shade, ventilation, and a maintainable exterior surface.
Rather than asking one component to perform every function, Atlas separates those functions into two complementary systems.
Have a question or observation?
The Atlas Construction System continues to evolve. If something in this article raised a question, or you would like to discuss the system with us, we welcome the conversation.
The Ventilated Roof System
