TL;DR
Type X drywall is 5/8-inch gypsum board reinforced with glass fibers in its core so it holds together in fire long enough to earn a one-hour rating in tested wall and ceiling assemblies. The IRC requires it most familiarly on garage ceilings beneath habitable rooms, per R302.6, and it lines party walls, furnace rooms, and stairwells in multifamily work.
What it means
Type X drywall is 5/8-inch gypsum board reinforced with glass fibers in its core so it holds together in fire long enough to earn a one-hour rating in tested wall and ceiling assemblies. The IRC requires it most familiarly on garage ceilings beneath habitable rooms, per R302.6, and it lines party walls, furnace rooms, and stairwells in multifamily work. The fibers keep the calcined core intact as the board's water of crystallization steams away, which ordinary gypsum panels cannot do; the rating belongs to the whole assembly, fasteners and framing included, not the sheet alone.
Where it sits in the glossary
Type X drywall is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
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