Thickness differences, sound and fire ratings, sag resistance on ceilings, weight per sheet, and building code situations that require 5/8 Type X gypsum board.
1/2 inch gypsum on walls and ceilings is the residential default when joists and studs are 16 inches on center. It balances weight, cost, and rigidity. A 4×8 sheet weighs about 57 lbs.
Use 1/2 inch moisture-resistant (green board) in bathrooms behind tile backer zones per manufacturer guidance — not as a tile substrate by itself in wet showers.
5/8 inch — fire, sound, and span
5/8 inch board adds mass for STC sound reduction between units and meets Type X fire ratings when labeled. Required on garage ceilings with living space above in many IRC jurisdictions.
Heavier sheets (≈70+ lbs per 4×8) need two people on ceilings. Screw spacing may tighten to 7 inches on ceiling per some codes.
Garage-to-house separation: often 5/8 Type X
Party walls in townhomes: check STC/fire assembly
24-inch joist spacing on ceilings: 5/8 recommended
Shaft walls and furnace closets: verify fire design
Frequently asked questions
Can I use 1/2 inch on a garage ceiling?
Many codes require 5/8 Type X on garage ceilings under finished living space. Check your local amended IRC before ordering.
Does thicker drywall reduce sound?
Mass helps, but resilient channel, insulation, and decoupled assemblies matter more. 5/8 on a single stud wall helps modestly; double layers with Green Glue or staggered studs help more.
Drywall Calculator provides estimates for planning only — not professional drywall contracting advice. Verify quantities and code requirements locally. Read disclaimer
