How Thick are Deck Boards? Examining Common Sizes and Materials

When constructing a new deck or replacing old deck boards, one of the most important decisions is selecting the thickness of the deck boards. The thickness impacts the look, durability, and cost of a deck, so it's an important factor to get right.

Standard Deck Board Thicknesses

Decking comes in a range of standard thicknesses, depending on the material used. Here are some of the typical sizes:

5/4 inch thickness

Many natural wood deck boards, including cedar, redwood, and pressure-treated pine, come in a standard thickness of 1 inch, also called 5/4 inch. The thickness is measured before the wood is planed smooth during manufacturing. Once planing is complete, the net thickness is about 3/4 inch to 7/8 inch.

5/4 inch provides a good balance of stability and affordability for traditional wood decking. The thickness is substantial enough to handle foot traffic without excessive bounce or flexing.

Cedar and redwood are naturally rot-resistant woods that make durable and attractive deck boards. Pressure-treated pine has been infused with preservatives to resist rot and insects. All three are commonly used for decking in a 5/4 inch thickness.

2x4 and 2x6 lumber thicknesses

Standard dimensional lumber, such as 2x4s and 2x6s, can also be used for deck boards. These boards are cut from larger timbers and planed to a finished thickness of 1.5 inches for 2x4s and 1.5 inches for 2x6s.

The width also varies - 2x4s are approximately 3.5 inches wide, while 2x6s are 5.5 inches wide. The larger 2x6 provides more stability underfoot.

Pressure-treated pine is a common choice, as is naturally rot-resistant cedar or redwood. Using dimensional lumber reduces waste since standard-sized boards are readily available.

Composite decking thicknesses

Composite deck boards, made from a mix of wood fibers and recycled plastic or other polymers, are also popular for their durability and low maintenance. The majority of composites are available in .93 to 1 inch thick boards.

Some brands offer thinner grooved boards around .67 inch, while exotic hardwood composites may be 1.3 inches thick. The thicker boards can span greater distances between deck joists.

Composite decking provides long-lasting performance. The mix of materials results in very stable boards that resist swelling, shrinking, splintering, and rotting.

Material Considerations for Thickness

The thickness required for deck boards depends partly on the material used. Consider these factors for choosing the optimal thickness:

Hardwoods vs. softwoods

Hardwood decking like ipe, tigerwood, and massaranduba is naturally dense and rigid. These boards can span greater distances without sagging and do not require as thick a profile as softwoods.

Softwoods like cedar and treated pine are less rigid by comparison. A thicker board provides more stiffness to prevent excessive bouncing or flexing underfoot. Softer woods usually require a 1 inch thickness for optimal performance in decking.

Composite decking thickness

Although composites are manmade, they act similarly to softwoods in terms of the need for thickness to prevent flexing. Most quality composite boards are at least .93 - 1 inch thick. This provides enough rigidity for optimal performance.

Thinner grooved boards around .67 inches are also available for use on diagonal deck patterns. Pairing these with a plywood substrate helps compensate for the thinner profile.

Thickness for load-bearing strength

The thickness of a deck board impacts its ability to withstand weight and force. Thicker boards can generally span greater distances between joists and support more weight than thinner versions of the same material.

For heavy items like hot tubs or crowded areas, choosing the thickest option available provides extra strength and minimizes chances of breakage. This may mean choosing 2x6 boards instead of 2x4s, or exotic composite boards rather than standard versions.

Design Factors for Deck Board Thickness

In addition to material choices, the intended design for a deck also influences appropriate board thicknesses. Key factors to consider include:

Span lengths

The distance between supporting joists under deck boards is called the span. Longer spans require thicker boards to prevent sagging or excessive bounce. Consult deck codes for allowable spans based on board thickness and material.

Appearance and texture

Thicker boards have deeper wood grain or more pronounced composite embossing. This provides a richer, more natural look. Thinner boards have a more uniform appearance.

Grooves cut into thinner composite boards add back visual texture. Tradeoffs between thickness and appearance should align with aesthetic preferences.

Cost considerations

Thicker deck boards often come at a higher price per linear foot. They may also require additional joists to maintain proper support, adding to material costs. However, thicker boards can provide more years of service, helping justify the investment.

Thinner boards reduce upfront material purchase requirements. This may fit better within a fixed deck project budget, although lifetime costs could be higher with earlier replacement needs.

Recommended Thicknesses by Deck Material

When selecting a thickness, consult manufacturer guidelines for recommendations based on the specific decking material you choose. Some general suggestions include:

Cedar deck boards

Western red cedar is available in 4/4 and 5/4 thicknesses. For residential decking, 5/4 inch boards are preferable. The thinner option is best reserved for vertical siding applications.

Pressure-treated deck boards

Pressure-treated pine for decking usually comes in 1 inch 5/4 inch planks. This provides sufficient thickness for strength and performance with properly spaced joists.

Composite decking recommended thicknesses

Quality composite brands offer boards ranging from .93 - 1.3 inches thick. While thinner options exist, it's best to choose boards at least 1 inch thick, or follow the manufacturer's recommendations for optimal results.

Exotic hardwood composites can be installed at a 1.3 inch thickness for additional rigidity on larger decks. Grooved thinner boards should be supported underneath with plywood when spanning 16 inches or more.

Choosing the Right Thickness for Your Project

Selecting the ideal deck board thickness involves striking the right balance for your specific needs. Keep these tips in mind:

Evaluating deck use, traffic, and load

How the deck will be used helps determine the right thickness. Heavily trafficked decks or those supporting hot tubs require thicker boards for strength. Standard thickness boards suffice for more occasional foot traffic.

Accounting for joist spacing

Thicker boards allow greater spans between joists. Work with deck codes to determine allowable spans, then choose thickness accordingly. Wider joist spacing may require upgrading to thicker boards.

Softwoods generally require thicker boards than hardwoods. Composites should be at least 1 inch thick for proper performance. Consult manufacturer guidelines for thickness pairing with specific materials.

Balancing all the factors of decking use, design, and materials will point you toward the ideal thickness for installing durable, long-lasting boards. Considering thickness early on ensures your deck's structural integrity and functionality for years to come.