Concrete shell

The shells are most commonly monolithic domes, but may also take the form of hyperbolic paraboloids, ellipsoids, cylindrical sections, or some combination thereof.

Concrete shell construction techniques are well suited for complex curves and are also used to build boat hulls (called ferroconcrete).

[2] Like the arch, the curved shapes often used for concrete shells are naturally strong structures,[3] allowing wide areas to be spanned without the use of internal supports, giving an open, unobstructed interior.

On the other hand, the seamless construction of concrete domes prevents air from escaping, and can lead to buildup of condensation on the inside of the shell.

Shingling or sealants are common solutions to the problem of exterior moisture, and dehumidifiers or ventilation can address condensation.

[7] A monolithic structure, it appears to have been sculpted in place by applying thin layers on top of each other in decreasing diameter.

[8] Massively thick at the bottom and thinning (with aerated volcanic pumice as part of the concrete mix) at the top, the Pantheon is a remarkable feat of engineering.

Advocates of these domes consider them to be cost-effective and durable structures, especially suitable for areas prone to natural disasters.