Difference Between Drywall and Gypsum Board: A Complete Guide

The Short Answer: Are Drywall and Gypsum Board the Same?

In everyday construction parlance, the terms are used interchangeably, but technically, they refer to two distinct concepts. Gypsum board is the specific manufactured building material—a panel consisting of a noncombustible calcium sulfate dihydrate core encased in paper or glass-mat facers. Drywall, conversely, refers to the entire building system and the method of construction. It is a colloquial North American term that emerged in the mid-20th century to distinguish this panel-and-joint-compound system from traditional "wet" lath-and-plaster methods.

Semantic vs. Technical: Breaking Down the Terminology

To specify materials accurately on architectural drawings or procurement orders, understanding the semantic boundaries is critical. The Gypsum Association strictly uses "gypsum board" in its technical literature to encompass the full spectrum of panel types, whereas contractors use "drywall" to describe interior partition finishing.

Regional and Brand Variants

• Sheetrock: A registered trademark of the United States Gypsum Company (USG). Often used generically in the U.S., similar to Kleenex, but technically refers only to USG's specific product line.
• Plasterboard: The standard terminology in the United Kingdom, Australia, and New Zealand. It refers to the exact same gypsum-core panel.
• Wallboard: A generic catch-all term used in building codes to describe any rigid panel material used to surface interior walls, which can technically include cement board or fiberboard, though it usually implies gypsum.

Core Manufacturing and Composition Standards

Regardless of the terminology used on the job site, the manufacturing process is governed by strict chemical and physical standards. The core is primarily composed of gypsum (calcium sulfate dihydrate). During manufacturing, the raw gypsum is calcined to remove roughly 75% of its chemically combined water, creating stucco (calcium sulfate hemihydrate).

When mixed with water, foaming agents, and specific additives, the slurry rehydrates and crystallizes between two continuous sheets of facing material. According to ASTM C1396 (the standard specification for gypsum board), the resulting panel must meet rigorous criteria for surface water absorption, core hardness, and flexural strength. The chemically combined water within the core is what gives gypsum board its inherent fire-resistive properties; when exposed to fire, the water calcines and releases as steam, actively retarding heat transmission.

Comprehensive Product Guide: Types of Gypsum Board in 2026

Selecting the correct panel requires moving beyond the generic "drywall" label. Modern manufacturing has bifurcated the market into highly specialized panels. Below is a technical matrix of the primary gypsum board categories available for specification in 2026.

Application Decision Framework: Which Board to Specify?

Architects and lead contractors should utilize the following decision logic to prevent costly tear-outs and code violations. Relying on standard drywall in specialized environments is a primary cause of mold litigation and fire-code failures.

1. Evaluating Fire and Life Safety Requirements

If the building code mandates a fire-resistance-rated assembly (e.g., separating a residential garage from the living space, or enclosing an elevator shaft), standard gypsum board is strictly prohibited. You must specify Type X or Type C. The critical difference lies in the core shrinkage under extreme heat. Standard cores shrink and crack, exposing the paper to flames. Type X utilizes fiberglass strands to hold the calcined core together. Type C adds vermiculite, which expands when heated, compensating for the shrinkage of the gypsum and maintaining the integrity of the barrier for up to four hours in specialized multi-layer assemblies.

2. Managing Moisture and Mold Vectors

The industry has largely moved away from traditional "green board" (moisture-resistant paper-faced gypsum) for high-risk commercial applications. While green board is acceptable for residential bathroom walls outside the direct shower spray zone, commercial projects and wet-area tile backers now mandate glass-mat gypsum board. Because glass-mat panels eliminate the organic paper facing entirely, they score a 10 out of 10 on the ASTM D3273 mold resistance test, effectively removing the food source that black mold requires to propagate.

3. Optimizing for Ceiling Framing and Weight

For ceiling applications framed at 24 inches on-center (O.C.), standard 1/2-inch gypsum board will sag over time due to gravity and ambient humidity. You must either step up to 5/8-inch board or utilize specialized Ultra-Light 1/2-inch ceiling board. Ultra-light formulations replace a portion of the gypsum core with microscopic hollow glass spheres and expanded polystyrene, reducing panel weight by up to 25% while maintaining the flexural rigidity required for 24-inch O.C. framing.

Fastener and Installation Specifications

The best gypsum board will fail if the fastener schedule is incorrect. The drywall system relies on specific mechanical connections to transfer shear and wind loads to the framing.

• Screw Selection: Use Type S (fine-thread) screws for light-gauge steel framing (20-gauge and thinner) and Type W (coarse-thread) screws for wood framing. Using wood screws on steel will strip the metal; using steel screws on wood will result in poor withdrawal resistance.
• Penetration Depth: Fasteners must penetrate wood framing by a minimum of 5/8 inch and steel framing by a minimum of 3/8 inch. For 1/2-inch gypsum board, use 1-1/4 inch screws. For 5/8-inch board, use 1-5/8 inch screws.
• The "Dimple" Rule: The screw head must break the paper face and create a shallow dimple without tearing the paper. If the paper is torn, the screw loses its holding power, and the joint compound will eventually crack over the fastener head.
• Spacing Schedule: For standard 1/2-inch wall applications on 16-inch O.C. wood framing, space screws at 16 inches in the field and 8 inches on the edges. For ceilings, reduce field spacing to 12 inches to combat gravitational sag.

Frequently Asked Questions

Can I use standard drywall behind a shower surround?

No. While some local residential codes historically allowed moisture-resistant green board behind acrylic tub surrounds, modern best practices and commercial codes require a cementitious backer board or a specialized glass-mat gypsum panel (like USG Fiberock or Georgia-Pacific DensShield) with a continuous liquid-applied waterproofing membrane. Standard paper-faced drywall will wick moisture through capillary action and fail structurally.

Why is 5/8-inch drywall often called "fire code" board?

This is a slight misnomer. The thickness itself does not provide the fire rating; the core composition does. However, 5/8-inch Type X gypsum board is the standard baseline for achieving a 1-hour fire-resistance rating on a standard wood-stud wall assembly. The additional 1/8-inch of thickness provides more calcined water to absorb heat, delaying the temperature rise on the unexposed side of the wall.

Is there a difference in soundproofing between drywall and gypsum board?

Since they are the same material, the terminology doesn't change the acoustics. However, if sound transmission class (STC) is a priority, you should specify sound-dampening gypsum board. These specialized panels feature a viscoelastic polymer layer sandwiched between two thin gypsum cores, which dissipates acoustic energy as low-grade heat, drastically reducing sound transfer compared to standard panels of the same thickness.