How does fire spread differ between masonry walls and wood-framed walls?

• A. Masonry walls resist fire and slow spread; wood walls burn and weaken faster
• B. Masonry walls burn quickly; wood walls resist fire
• C. Both spread at the same rate
• D. Wood-framed walls never catch fire

Answer: (A)

Fire spread through walls depends on whether the wall is noncombustible and has mass versus being built with combustible framing. Masonry walls, like brick or concrete block, don’t burn and resist heat well. Their mass absorbs heat slowly, which slows the temperature rise on the interior side and delays ignition of any materials inside. Since the wall itself isn’t a fuel, the fire has a harder time propagating through it, giving more time to stop it and contain it.

Wood-framed walls use wood studs and other combustible components. Wood is a fuel, so it heats up quickly, chars, and loses structural strength under fire. The cavities within a wood-framed wall can also act as channels for flames and heat to travel more rapidly from one side to the other, leading to faster fire growth and earlier loss of stability.

So, masonry walls resist fire and slow spread, while wood-framed walls burn and weaken faster.