Types of Drywall: Type X, Type C, Moisture & Mold Resistant
"5/8" GWB" on a drawing can mean half a dozen different products at very different prices. The wall type legend and specs tell you which board goes where, and a drywall takeoff should keep each type as its own line item.
The main types
| Type | Common thickness | Where it's specified |
|---|---|---|
| Regular gypsum board | 1/2", 5/8" | Standard walls and ceilings, residential and light commercial |
| Type X (fire-rated) | 5/8" | Rated walls and ceilings (1-hour and up), corridors, garages, between units |
| Type C (enhanced fire) | 1/2", 5/8" | Specific UL designs, often rated ceilings; more fire resistance than Type X |
| Moisture / mold resistant | 1/2", 5/8" | Bathrooms, kitchens, wet walls (not direct water exposure) |
| Abuse / impact resistant | 5/8" | Corridors, schools, common areas; often to 4' AFF or full height |
| Shaftliner | 1" | Shaft walls and area separation walls with C-H studs |
| Cement / glass-mat backer | 1/2", 5/8" | Tile substrate in showers and wet areas |
| Glass-mat exterior sheathing | 1/2", 5/8" | Exterior walls behind the air/water barrier |
Reading which type goes where
- Wall type legend: each assembly lists its board, e.g. "5/8" Type X gypsum board each side." See how to read a wall type legend.
- General notes: blanket rules like "provide moisture-resistant board at all wet walls" or "abuse-resistant board to 4'-0" AFF in corridors."
- UL designs: a rated wall's UL number fixes the board type and number of layers. Don't substitute.
Takeoff tips
- Keep each board type separate: the same wall can take Type X on one face and moisture-resistant on the other.
- Watch partial-height rules ("abuse-resistant to 4' AFF") that split one face into two products.
- Two-layer assemblies double the board count for that wall type.
- Sheets = wall length × height × faces ÷ sheet area, plus waste. The drywall calculator does the per-wall math.
Quick answers
What is Type X drywall?
Fire-rated 5/8" gypsum board with glass fibers in the core, used in fire-rated wall and ceiling assemblies such as between apartments, in corridors and in garages.
What's the difference between Type X and Type C drywall?
Type C has more glass fiber and additives than Type X, so it holds together longer in a fire. It's required by certain UL designs, especially rated ceilings.
Is green board waterproof?
No. Moisture-resistant board resists humidity and incidental moisture, but it isn't for direct water exposure like shower walls, which need cement or glass-mat backer.
What thickness is commercial drywall?
5/8" is standard in commercial work, and it's the thickness used for Type X fire-rated assemblies; 1/2" is common in residential walls.
Count it from the plans instead
Upload a digital plan set and ReadMyBlueprint measures every wall, matched to the plan's own wall types. Your first plan set is free.
Try it freeRelated: Reading a wall type legend · Free calculators · How to do a takeoff · Glossary