Which architectural element is typically used to resist lateral thrusts in a cathedral wall?

• A. Barrel Vault
• B. Buttress
• C. Rib Vault
• D. I-beam

Answer: (B)

Lateral thrust from vaulted ceilings pushes outward on cathedral walls, so a structure needs an external element to counter that push and keep the walls from bowing outward. A buttress fits this role perfectly: it acts as a stiff external support that takes the outward force and transfers it down to the foundation, stabilizing the wall. In many cathedrals you’ll see flying buttresses, which channel the thrust away from the wall to taller exterior supports, but the essential function remains counteracting the horizontal push from the vault. Barrel vaults and rib vaults are the methods used to cover space, but they generate the outward thrust that must be resisted, rather than providing the resistive force themselves. An I-beam is a modern structural member used to resist bending in frame structures, not a traditional device for countering lateral thrust in cathedral walls.