The Fundamental Difference
Plaster and drywall both create smooth interior wall and ceiling surfaces, but they differ fundamentally in composition, installation method, skill required, and performance characteristics. Understanding these differences helps you make the right choice for renovations, new builds, and historical restoration projects.
How Traditional Plaster Works
Traditional plaster (also called three-coat plaster) is applied in three successive layers over a lath substrate:
- Scratch Coat: The first coat is scratched with a comb to provide mechanical keys for the next layer. Mixed from gypsum or lime with aggregate.
- Brown Coat: The second coat levels the wall surface. Applied after the scratch coat sets.
- Finish Coat: The final thin coat, often pure gypsum or lime putty, is polished to a glass-smooth surface.
The entire process takes 3–5 days, as each coat must be allowed to set and cure before the next is applied. This is why plaster walls are significantly more expensive and slower to install than drywall.
How Drywall Works
Drywall (also called gypsum board or sheetrock) consists of a gypsum plaster core sandwiched between two layers of paper. Sheets are screwed to wall studs, taped at the joints, coated with joint compound (mud), sanded smooth, and primed. A skilled drywall crew can install and finish drywall in a fraction of the time required for plaster.
Head-to-Head Comparison
| Factor | Plaster | Drywall |
|---|---|---|
| Material Cost (per sq ft) | $5–$10 | $1.50–$3 |
| Labor Cost (per sq ft) | $7–$16 | $2–$5 |
| Total Installed Cost | $12–$26/sq ft | $3–$8/sq ft |
| Installation Time | 3–7 days per room | 1–2 days per room |
| Skill Required | Very High (specialist plasterer) | Moderate (general contractor) |
| Thickness | 7/8 inch (3 coats) | 1/2 inch standard |
| Sound Insulation (STC) | Superior (denser mass) | Good (can add layers) |
| Fire Resistance | Excellent | Good (Type X = 1 hr) |
| Moisture Resistance | Good (lime plaster) | Poor (standard) / Good (moisture board) |
| Crack Resistance | Prone to hairline cracks | Joint seams can crack |
| Historical Accuracy | Authentic for pre-1950 homes | Not period-accurate |
| DIY-Friendly | Not recommended | Moderate DIY feasibility |
When to Choose Plaster
- Restoring a historic home where plaster is required to maintain period authenticity
- High-end custom projects where superior acoustics and hardness are priorities
- Curved or ornamental architectural details that drywall cannot replicate
When to Choose Drywall
- New residential or commercial construction — the speed and cost savings are substantial
- Any renovation project where budget is the primary concern
- When you need quick completion with modern fire and moisture resistance
Estimating Drywall for a Room
To estimate drywall sheets needed:
- Calculate total wall + ceiling area in square feet.
- Subtract door areas (21 sq ft each) and window areas (15 sq ft each).
- Divide by 32 (for 4×8 sheets) or 48 (for 4×12 sheets).
- Add 10% for waste and cuts.
Use our free Plaster Calculator to estimate plaster coat quantities, or our estimating tools for drywall projects.