How Thick Is Drywall in the USA? A Detailed Guide to Standard Drywall Thicknesses

Understanding Drywall Thickness in the American Construction Industry

In the United States, drywall, also known as gypsum board or Sheetrock, is a fundamental material in residential and commercial construction. It forms the interior walls and ceilings of nearly every modern building. One of the most critical aspects of drywall selection is its thickness, which affects everything from structural integrity and fire resistance to soundproofing and installation method.

In this comprehensive guide, we outline the standard drywall thicknesses used in the USA, explore their most common applications, and provide insight into the building codes and performance requirements that influence drywall choice.

Common Drywall Thicknesses in the USA

Drywall in the United States typically comes in several standardized thicknesses. Each serves a distinct purpose in different areas of construction and remodeling.

1. 1/4-Inch Drywall (6.4 mm)

• Typical Use: Ideal for curved surfaces, arches, and for layering over existing drywall or plaster during renovations.
• Flexibility: This is the thinnest and most flexible drywall available, making it easy to bend and shape.
• Limitations: Due to its lack of structural strength, it is not suitable for standalone installation on walls or ceilings.

2. 3/8-Inch Drywall (9.5 mm)

• Common Applications: Used in older homes where walls or ceilings have non-standard spacing or require a slightly thicker repair layer.
• Surface Compatibility: Often selected when replacing drywall in remodeling projects, especially where old lath and plaster walls need a thinner board.
• Limitations: Not used frequently in new construction due to insufficient rigidity for modern framing standards.

3. 1/2-Inch Drywall (12.7 mm)

• Standard Thickness: This is the most common drywall thickness in residential construction across the USA.
• Versatility: Suitable for most interior walls and ceilings, including bedrooms, hallways, and living rooms.
• Installation Benefits: Offers a solid balance between weight, sound control, and structural strength, making it manageable for DIY installation and professional use.

4. 5/8-Inch Drywall (15.9 mm)

• Fire-Rated Drywall: This thickness is typically used where fire resistance is a requirement, such as between a garage and a living space.
• Soundproofing Capabilities: Thicker boards reduce noise transmission, making them perfect for multi-family housing, commercial buildings, and home theaters.
• Code Compliance: Often required by building codes in commercial construction and in residential spaces where Type X or fire-rated drywall is specified.

Specialty Drywall Types and Their Thicknesses

While standard drywall thicknesses are sufficient for most construction needs, specialized applications may require fire-rated, moisture-resistant, or impact-resistant drywall, which can also vary in thickness.

Type X Drywall (Typically 5/8-Inch)

• Purpose: Engineered with fiberglass additives to increase fire resistance.
• Use Case: Required by code in apartment buildings, corridors, exit stairways, and shared walls.
• Burn Rating: Usually offers a 1-hour fire rating per sheet when properly installed.

Greenboard and Purple Board (Moisture-Resistant)

• Thicknesses Available: Typically 1/2-inch or 5/8-inch, designed to resist moisture and mold growth.
• Installation Areas: Bathrooms, laundry rooms, basements, and utility closets.

Soundproof Drywall

• Multiple Layers: Made with sound-dampening cores and sometimes composite layers, often 5/8-inch thick.
• Noise Reduction: Reduces transmission of sound between rooms and units in multi-family dwellings.

Drywall Thickness by Application

Understanding which drywall thickness to use in different parts of a building is essential for meeting code, ensuring durability, and achieving desired performance outcomes.

Interior Residential Walls

• Recommended Thickness: 1/2-inch drywall is the industry standard.
• Rationale: Provides enough strength for standard wood or metal framing, easy to install, and cost-effective.

Ceilings

• Recommended Thickness: Minimum 1/2-inch, but 5/8-inch is preferred to prevent sagging, especially with insulation above.
• Note: Some manufacturers produce lightweight 1/2-inch drywall that resists sagging and is UL-rated for ceiling applications.

Shared Walls (Duplexes, Apartments)

• Recommended Thickness: 5/8-inch Type X drywall for fire resistance and acoustic performance.
• Installation Requirement: Sometimes installed in double layers to meet fire rating and soundproofing codes.

Garage and Basement Walls

• Recommended Thickness: 5/8-inch Type X, especially where the wall serves as a fire barrier.
• Building Code: Most local codes require fire-rated drywall between an attached garage and the main living area.

Drywall Size and Framing Considerations

The thickness of drywall must align with the spacing of wall studs or ceiling joists, which are typically placed 16 or 24 inches apart on center. Thicker drywall ensures rigidity and minimizes the risk of nail pops, cracking, or sagging, especially in ceiling installations.

Stud Spacing Recommendations

• 16” On Center (OC): Suitable for all drywall thicknesses.
• 24” OC: Requires 5/8-inch drywall for ceilings to prevent sagging over time.

Impact of Building Codes on Drywall Thickness

In the United States, building codes such as the International Residential Code (IRC) and International Building Code (IBC) establish minimum requirements for drywall usage.

• Fire Separation Requirements: Codes mandate fire-rated drywall in certain walls and ceilings to protect occupants and contain fire spread.
• Ceiling Sag Prevention: To meet UL fire ratings and avoid deformation, ceilings with insulation must use 5/8-inch drywall when studs are spaced 24 inches apart.
• Sound Transmission Class (STC) Ratings: Thicker drywall contributes to higher STC ratings, a critical factor in multi-unit dwellings and commercial spaces.

Conclusion

The question “How thick is drywall in the USA?” does not have a one-size-fits-all answer. While 1/2-inch drywall remains the most common for interior residential use, various thicknesses and types exist to meet the demands of modern construction. Whether you are building new, remodeling, or working under strict code requirements, understanding the role of drywall thickness is essential for structural performance, fire safety, sound insulation, and long-term durability.

Disclaimer: This article is for informational and educational purposes only and is not intended to provide legal advice.