Drywall covers more interior surface area in American homes than any other material, yet most homeowners have no idea what is behind that smooth, painted finish. Understanding what is drywall made of matters when you are choosing panels for a renovation, repairing damage, or deciding between standard and specialty types for bathrooms, garages, and basements.
The Basic Composition of Drywall
At its core, drywall is remarkably simple. A layer of gypsum plaster is sandwiched between two sheets of heavy paper or fiberglass mat. Gypsum (calcium sulfate dihydrate, CaSO4 plus 2H2O) is a naturally occurring mineral mined from quarries across the United States, with major deposits in Oklahoma, Texas, Iowa, and Nevada.
The gypsum core makes up roughly 90 percent of the panel’s weight. During manufacturing, raw gypsum is heated to about 350 degrees Fahrenheit to drive off most of its chemically bound water, creating a powder called calcined gypsum or plaster of Paris. This powder is mixed with water, starch, and various additives, then spread between paper sheets on a conveyor belt. The slurry rehydrates and hardens as it moves down the line, forming rigid panels that are cut to size and kiln-dried.
What Each Layer Does
The Gypsum Core
Gypsum provides fire resistance, dimensional stability, and soundproofing. Each molecule of gypsum contains about 21 percent water by weight. During a fire, this chemically bound water releases as steam, which absorbs heat and slows temperature rise on the unexposed side of the wall. A single 5/8-inch sheet of Type X drywall can resist fire penetration for up to 1 hour.
The Paper Facing
Standard drywall uses recycled paper on both sides. The face paper (the side you see after installation) is a smooth, off-white manila-type paper that accepts paint, texture, and joint compound. The back paper is a coarser, gray kraft paper that bonds to the gypsum core and provides structural integrity.
Additives in the Core
Modern drywall includes several additives mixed into the gypsum slurry:
- Starch — improves the bond between the gypsum core and paper facing
- Glass fibers — added to fire-rated (Type X) panels for crack resistance at high temperatures
- Wax emulsion — provides limited moisture resistance in standard panels
- Foaming agents — create tiny air bubbles in lightweight drywall, reducing weight by up to 30 percent
- Fungicides — added to moisture-resistant and mold-resistant panels to inhibit mold growth
Types of Drywall and Their Uses
Standard White Drywall
The most common type, used for interior walls and ceilings in dry areas. Available in 1/4-inch, 3/8-inch, 1/2-inch, and 5/8-inch thicknesses. Most residential walls use 1/2-inch panels. A standard 4×8-foot sheet costs $10 to $15 at home improvement stores.
Moisture-Resistant (Green Board)
Identifiable by its green paper facing, this type uses a water-resistant paper and wax-treated core. It is designed for bathrooms, kitchens, and laundry rooms where humidity is elevated but direct water contact is not expected. Green board costs $14 to $20 per 4×8 sheet. Note: it is not waterproof and should not be used as a tile backer in shower surrounds.
Fire-Rated (Type X)
Required by building codes for garage-to-house shared walls, furnace rooms, and multi-family party walls. Type X drywall contains glass fibers and a denser gypsum core that provides 1-hour fire resistance in 5/8-inch thickness. Costs $14 to $18 per 4×8 sheet. Type C offers even greater fire resistance with additional vermiculite in the core.
Mold-Resistant (Purple Board)
Features fiberglass mat facing instead of paper, eliminating the organic food source that mold feeds on. The core also contains mold-inhibiting additives. Purple drywall from brands like Gold Bond and National Gypsum is the best choice for basements, bathrooms, and any below-grade application. Priced at $15 to $25 per 4×8 sheet.
Soundproof Drywall
Products like QuietRock and CertainTeed SilentFX use a viscoelastic polymer layer between two gypsum sheets that dampens sound vibration. A single sheet of 5/8-inch QuietRock achieves sound transmission class (STC) ratings comparable to double layers of standard drywall. At $40 to $60 per 4×8 sheet, it is expensive but saves labor by eliminating the need for double-layer installation.
Standard Drywall Sizes
Drywall panels come in standard widths of 4 feet and lengths of 8, 10, 12, and 14 feet. Longer panels reduce the number of seams in a room, which means less taping and finishing work. A 4×12-foot panel covers an entire 12-foot wall in one piece, eliminating the butt joint that a pair of 4×8-foot sheets would create.
Ceiling installations often use 54-inch-wide panels (4.5 feet) to reduce the number of seams on wide ceilings. Lightweight drywall panels weigh about 30 percent less than standard — a 4×8-foot half-inch lightweight sheet weighs approximately 38 pounds versus 57 pounds for standard, making overhead installation significantly easier.
Environmental and Health Considerations
Drywall manufacturing recycles a significant amount of material. Synthetic gypsum from coal-fired power plant flue gas desulfurization (FGD) accounts for roughly 45 percent of the gypsum used in US drywall production. The paper facing comes primarily from recycled newspaper and corrugated cardboard.
Concerns about Chinese drywall imported between 2001 and 2009 led to stricter standards. Those problematic panels emitted sulfur compounds that corroded copper wiring, blackened silver, and caused respiratory irritation. Domestically produced drywall and current imports meeting ASTM C1396 standards do not have these issues. If you are renovating a home built between 2001 and 2009 and suspect Chinese drywall, look for a sulfur smell and blackened copper pipes as telltale signs.
Working With Drywall: Quick Tips
Knowing what is drywall made of helps you work with it more effectively. Score the paper face with a utility knife and snap the panel along the cut — the gypsum breaks cleanly along the scored line. For curves, wet the back paper with a sponge and bend slowly — the moistened gypsum becomes temporarily flexible. Use coarse-thread drywall screws every 8 inches along studs, driving them just below the paper surface without breaking through. Broken paper means a weak fastening point that will pop later under joint compound.
