Actual Size of Deck Boards in Construction in the USA

When it comes to building a deck, understanding the actual size of deck boards is essential for ensuring precision in design, material selection, and structural integrity. While nominal sizes are used as standard industry terms, the actual dimensions of deck boards can significantly affect the overall construction process. Knowing these precise measurements ensures a smooth installation and long-lasting results for deck construction in the United States.

What Are Deck Boards?

Deck boards are the primary surface material used in the construction of outdoor decks. These boards are laid across joists to create a flat surface for walking or seating. The materials for deck boards vary, with wood, composite, and PVC being the most common options used for residential and commercial deck building in the USA.

The size of the deck board plays a crucial role in the deck’s aesthetic appeal, structural integrity, and overall functionality. Deck boards are typically available in various nominal sizes, which differ from their actual size after the lumber has been processed.

Understanding Nominal Size vs. Actual Size

The nominal size refers to the dimensions of the board as they are labeled, often rounded to the nearest inch. For example, a 2 x 6 deck board is marketed as a 2-inch by 6-inch board, but the actual dimensions are smaller once the wood is planed and dried. This reduction happens because wood shrinks during the drying process and is planed down to achieve a smoother, uniform surface.

For deck boards, common nominal sizes include:

• 2 x 6
• 5/4 x 6 (also known as 1-inch decking)
• 4 x 4 for posts
• 2 x 4 for railings and smaller structures

However, the actual size of deck boards is smaller than their nominal size. For example:

• 2 x 6 deck board: Actual size: 1.5 inches by 5.5 inches
• 5/4 x 6 deck board: Actual size: 1 inch by 5.5 inches

Understanding these actual sizes ensures that measurements and cuts are accurate, particularly when decking materials are being fastened to framing or other structural components.

Types of Deck Boards and Their Actual Sizes

Wood Decking

Wood decking is the most traditional and widely used material for constructing outdoor decks. Common types of wood used for deck boards include pressure-treated pine, cedar, redwood, and tropical hardwoods like ipe and mahogany.

Pressure-Treated Pine Decking

• Nominal size: 2 x 6
• Actual size: 1.5 inches by 5.5 inches
• Common for decks due to its affordability and availability. Pressure-treated pine is chemically treated to resist rot and pests, making it ideal for outdoor use.

Cedar and Redwood Decking

• Nominal size: 2 x 6
• Actual size: 1.5 inches by 5.5 inches
• Known for its natural resistance to decay, cedar, and redwood decking are popular for their aesthetic qualities and natural wood scent.

Tropical Hardwood Decking

• Nominal size: 2 x 6
• Actual size: 1.5 inches by 5.5 inches
• Hardwoods like ipe are dense, durable, and highly resistant to wear and environmental damage. These types of boards are perfect for long-lasting decks in harsh weather conditions.

Composite Decking

Composite decking has gained popularity due to its durability, low maintenance requirements, and resistance to rotting and splintering. These boards are made from a combination of wood fibers and plastic, and they come in a variety of colors and textures.

Composite Deck Boards

• Nominal size: 5/4 x 6
• Actual size: 1 inch by 5.5 inches
• Composite decking provides an aesthetic similar to wood, but it requires significantly less maintenance, making it an appealing choice for modern deck builders.

PVC Decking

PVC decking is made entirely of plastic and offers excellent resistance to moisture, stains, and mold. It is highly durable and requires little maintenance compared to traditional wood decking.

PVC Deck Boards

• Nominal size: 5/4 x 6
• Actual size: 1 inch by 5.5 inches
• PVC boards are lightweight, moisture-resistant, and come in a wide variety of colors and styles, making them ideal for homeowners who want an easy-to-maintain deck.

Deck Board Thickness and Span

The thickness of deck boards impacts their load-bearing capacity and the span between joists. Thicker boards generally allow for greater spacing between supporting beams, while thinner boards require closer spacing to ensure adequate support.

For example:

• A 1.5-inch thick wood deck board (such as a 2 x 6) typically requires joist spacing of 16 inches for optimal support.
• A 1-inch thick composite or PVC deck board often requires 12-inch joist spacing for maximum strength and stability.

Choosing the correct thickness of deck boards in relation to the joist spacing ensures that the deck will be sturdy and able to support the weight of furniture, people, and environmental factors like snow.

Other Considerations for Deck Board Construction

Expansion and Contraction

Wood is a natural material that expands and contracts based on changes in temperature and humidity. This is particularly important in the USA, where weather conditions vary greatly. Builders must leave gaps between boards to accommodate for this natural expansion and contraction.

For wood decking, it’s recommended to leave a gap of about 1/8 inch to 1/4 inch between each board to allow for expansion. For composite decking, the gap is typically around 1/4 inch to 3/8 inch.

Fasteners and Installation

The fasteners used for securing deck boards play a significant role in the deck’s durability and appearance. Screws and nails designed specifically for deck construction should be used to avoid rust and corrosion. Hidden fastener systems are also available, which provide a smooth surface without visible screws or nails.

For wooden deck boards, the recommended fasteners are:

• Galvanized screws for a rust-resistant hold.
• Decking clips for hidden fastening systems.

For composite and PVC boards, specialized screws designed for these materials help avoid cracking or warping.

Conclusion

Understanding the actual size of deck boards is vital for ensuring accurate measurements, proper material estimation, and successful deck installation. While nominal sizes are used for convenience, the actual dimensions of deck boards, such as 1.5 inches by 5.5 inches for a 2 x 6, should always be taken into account when planning and building decks.

From choosing the appropriate type of wood or composite material to understanding the expansion and contraction of decking, each detail contributes to the longevity and safety of the deck. With the correct knowledge and attention to detail, construction projects involving deck boards will lead to durable, aesthetically pleasing, and long-lasting outdoor spaces.