What is Drywall?
Drywall (also called gypsum board, plasterboard, or sheetrock) is the standard interior wall and ceiling finishing material in modern construction. It consists of a gypsum plaster core pressed between two thick sheets of paper. Drywall replaced traditional plaster-and-lath construction because it is faster to install, less expensive, and provides a smooth, paintable surface with minimal skill required for basic installation.
Standard drywall sheets measure 4 feet wide by 8 or 12 feet long, with 1/2-inch thickness being the most common for walls and 5/8-inch for ceilings and fire-rated assemblies. Specialty types include moisture-resistant (green board) for bathrooms, mold-resistant (purple board) for high-humidity areas, and fire-rated (Type X) for garage walls and ceilings. Choosing the right type for each application ensures code compliance and long-term performance.
Drywall Calculation Formula
Wall Area = Perimeter × Height - Door/Window Openings
Ceiling Area = Length × Width
Drywall Types & Thickness
| Type | Thickness | Use | Cost/Sheet (4x8) |
|---|---|---|---|
| Standard | 1/2" | Walls, general use | $10-$15 |
| Lightweight | 1/2" | Ceilings, easier handling | $12-$17 |
| Fire-Rated (Type X) | 5/8" | Garages, fire walls | $13-$18 |
| Moisture-Resistant | 1/2" | Bathrooms, kitchens | $14-$20 |
| Mold-Resistant | 1/2" | Basements, high humidity | $15-$22 |
Finishing Supplies Guide
For every 1,000 square feet of drywall, you will need approximately 3.5 gallons of premixed joint compound, 370 feet of paper tape, and 3.5 pounds of drywall screws. Corner bead (for outside corners), setting compound (for first coat), and sanding supplies add to the finishing material list. Budget approximately $0.40-$0.60 per square foot for all finishing materials combined.
Worked Example
A 15x12 ft room, 8 ft ceilings, with 1 door and 2 windows, using 4x8 sheets:
Wall area = 54 × 8 = 432 sq ft
Deductions: 1 door (21 sq ft) + 2 windows (30 sq ft) = 51 sq ft
Net wall area = 381 sq ft
Ceiling = 15 × 12 = 180 sq ft
Total = 561 sq ft ÷ 32 = 17.5 × 1.10 = ~20 sheets
Frequently Asked Questions
Should I use 4x8 or 4x12 sheets?
Use 4x12 sheets for 12-foot walls to reduce the number of joints. Fewer joints means less taping and finishing work, and a smoother final surface. However, 4x12 sheets are heavier and harder to handle, especially for ceilings. For most DIY projects with 8-foot ceilings, 4x8 sheets are easier to manage.
How much waste should I plan for?
Add 10% waste for rectangular rooms with few openings. Add 15% for rooms with many windows, doors, or irregular shapes. The waste percentage accounts for cutoffs around openings, damaged sheets, and fitting waste. Keep large cutoff pieces for patches and small areas.
Do I drywall walls or ceiling first?
Always hang the ceiling first, then the walls. The wall sheets will butt up against the ceiling sheets, helping support the ceiling edges. This also means any gap at the top of the wall sheets is hidden behind the ceiling drywall, creating a cleaner joint.
How many coats of joint compound do I need?
Three coats is standard for a Level 4 finish (suitable for most paint finishes). The first coat embeds the tape, the second fills and feathers, and the third provides a smooth final surface. For flat or matte paint, a Level 4 finish is adequate. For glossy paint or critical lighting, a Level 5 finish (skim coat over the entire surface) is recommended.