1/2 inch — default for most homes
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