Fire Rating (Fire-Resistance Rating)
The duration in hours that a building assembly (wall, floor, ceiling) can resist the passage of fire and maintain structural integrity, as determined by ASTM E119 testing.
In Detail
Common fire ratings: 1-hour (most residential demising walls), 2-hour (townhouse shared walls, commercial), 3-hour (high-rise). A 1-hour fire-rated wall typically consists of 2×4 framing with one layer of 5/8" Type X gypsum on each side. Adding insulation and additional drywall layers increases the rating.