Why Does Drywall Crumble After Fire Exposure?

Drywall's core is gypsum, a mineral that contains water molecules locked in its crystal structure. When fire heats the gypsum above about 176 degrees Fahrenheit, that water evaporates, and the gypsum dehydrates into a brittle powder. The paper layers on both sides also burn or char, removing the reinforcement that held the core together.

The result is a wall that looks discolored or slightly bulged but feels crumbly to the touch. The damage is often deeper than it appears, because the heat travels through the board and affects the entire thickness. Even a small fire can weaken a large area of drywall, making it unsafe to leave in place.

After a fire, firefighters often use water to extinguish flames, so you may have both heat damage and water damage in the same walls. The water soaks into the already dehydrated gypsum, causing it to soften and sag. That combination makes the drywall even more likely to crumble and fall apart.

The pros start by inspecting the fire-damaged area to determine how far the damage extends. They may use moisture mapping to see where water has penetrated and check for hidden pockets of dampness. After that, they remove the unsound drywall and clean the exposed framing.

Then they install new drywall, tape, and finish the joints, matching the existing texture. If the fire also caused water damage, they might set up dehumidifiers to dry the space fully before closing up the walls. The work usually involves both drywall replacement and structural drying, depending on what the inspection finds.

• Inspection to map heat and moisture damage
• Removal of crumbled drywall and cleaning of studs
• Drying of the wall cavity if water is present
• Installation of new drywall and finishing
• Check for smoke odor and soot residue