Drywall Thickness for Interior and Exterior Walls: A Comprehensive Guide

When it comes to wall construction, the choice of materials can significantly affect the overall durability, insulation, and cost of the building. Drywall, one of the most common materials used for interior walls, is often a topic of discussion when it comes to exterior walls as well. This article aims to clarify the differences (or lack thereof) in drywall thickness used for both interior and exterior walls and provide you with a comprehensive understanding of this important issue.

Standard Drywall Thicknesses

Generally, the thickness of drywall used for walls, whether they are inside or outside, is similar. Standard drywall thicknesses are typically 1/2 inch (12.7 mm) for interior walls and 5/8 inch (15.9 mm) for fire-rated applications, often used in specific areas such as shared walls in multifamily homes.

Exterior Walls: A Different Approach

For exterior walls, drywall is frequently not the primary wall material. Instead, exterior walls are typically framed with plywood or oriented strand board (OSB) sheathing, covered with weather-resistant barriers, and finished with siding or other exterior materials. This approach provides better protection against weather elements and increases the structural integrity of the wall.

However, in some instances, drywall is indeed used on exterior applications, such as in a garage. In these cases, 5/8 inch (15.9 mm) thick drywall is commonly employed for added fire resistance.

Why Drywall May Not Be Ideal for Exterior Walls

While drywall is commonly used inside buildings, many professionals advocate for the use of plywood or OSB for exterior walls. The strength of these materials is considered a reasonable trade-off for the cost of using drywall. Plywood and OSB offer enhanced moisture resistance and structural integrity, which are crucial for exterior applications.

Regulatory Requirements for Drywall Thickness

The choice of drywall thickness for interior versus exterior walls is not entirely based on aesthetic or structural differences alone. Regulatory requirements dictate the thickness of drywall, primarily to meet fire safety standards. For instance, 1/2 inch (12.7 mm) drywall is typically sufficient for interior spaces, while 5/8 inch (15.9 mm) drywall, often referred to as Type X, is required for fire-rated applications, especially in areas separating two dwellings in multifamily homes or in garages.

Conclusion

While the standard drywall thickness for interior and exterior walls is generally the same, the materials and construction techniques used for exterior walls may differ. Understanding the purpose and regulatory requirements of drywall thickness is crucial for both home builders and property owners. As you plan your next construction project, consider the benefits and drawbacks of using drywall on exterior walls to ensure optimal performance and safety.

Key Takeaways:

Drywall can be used on exterior walls but is not typically the first choice. Exterior walls often use plywood or OSB for enhanced durability and moisture resistance. 5/8 inch (15.9 mm) drywall is used for added fire resistance in some exterior applications. Regulatory standards require specific drywall thicknesses for fire safety.

By following these guidelines, you can ensure that your walls, whether inside or outside, meet the necessary standards and offer the best performance for your home or building.