Which type of building construction is considered most vulnerable during a fire?

Lightweight frame construction is considered the most vulnerable during a fire due to its inherent design and materials. This type of construction typically utilizes wood and other lightweight materials, which ignite and burn quickly. The structural integrity of lightweight frames can be compromised rapidly in a fire situation, as they do not have the same heat resistance as heavier materials.

In contrast, brick and concrete slab constructions are much more fire-resistant, as they are made from non-combustible materials that can withstand high temperatures without immediate structural failure. Steel frame constructions, while not immune to fire, have greater durability under fire conditions compared to lightweight structures. Steel can lose its tensile strength at elevated temperatures, but it generally maintains its structure longer than wood or lightweight methods.

Thus, the vulnerability of lightweight frame construction significantly increases the risk of rapid fire spread, early structural failure, and the potential for danger to firefighters and occupants during a fire.