Pantheon Secret #2: Making a Concrete Ceiling Lighter
The Pantheon’s concrete domed ceiling is an engineering marvel. Roman engineers knew a concrete dome would be far too heavy. And nobody wanted a massive building collapse. To help reduce the weight, designers used both art and construction secrets. First, they used a, artistic coffered ceiling. Coffers are square indentations that give the ceiling some visual interest.
Every square inch of concrete removed to create the coffers takes a little bit of weight off the dome. Second, the dome is a little thinner as it goes upward in height; it’s thicker at the base than at the top. Third, the oculus not only let in light and air, it also reduced the concrete in the ceiling. Finally, the most hidden secret is how the Romans blended hollow jugs, or amphora, in the concrete. The concrete was still super strong, but it lightened the amount of used in the dome.
