5 Mistakes to Avoid When Installing Pressure Treated Deck Boards

Building a new deck or replacing old deck boards provides the perfect opportunity to enjoy your outdoor space. With pressure treated lumber, you can have a surface that stands up to the elements while resisting insects, rot, and decay. However, proper installation is crucial. Avoid these common mistakes for the best results.

Not Allowing Wood to Dry Before Installation

When pressure treated deck boards are fresh from the lumber yard, they often still contain a high moisture content from the treatment process. If you install wet boards, as they dry out, the wood will shrink and open up unsightly gaps between the boards. In some cases, wet boards may also crack, warp or develop mold.

To avoid these issues, it's important to allow pressure treated wood to dry adequately before installation. Here are some tips:

• Request KDAT lumber, which is kiln dried after treatment to lower the moisture content.
• Stack boards with spacers in a dry, covered area for several weeks prior to building your deck.
• Use a moisture meter to test wood moisture content. Boards should read below 19% before installation.

Taking these simple steps allows the wood to stabilize and prevents shrinkage problems down the road. Your deck will look better and last longer.

Installing Boards Too Tightly Together

While you may expect deck boards to fit tightly together, leaving no gaps, this can actually cause significant issues over time. Pressure treated lumber shrinks as it dries out and weathers. If you install boards too close together initially, they will later shrink and open up wider, uneven gaps.

Deck boards also swell slightly when wet and shrink as they dry after rainfall or snow. Installing too tightly leads to buckling and unsafe gaps.

To avoidinstallation gaps, follow these best practices:

• Leave 1/8" spacing between deck boards to allow for expansion.
• Use plastic or composite decking if you want a gap-free surface.
• Follow manufacturer recommendations for proper board spacing.

Leaving a small gap preserves the beauty of your deck for many years.

Improper Joist Spacing

The joists or beams running beneath your deck boards provide crucial support. With improper joist spacing, deck boards can develop cracks, warp or bounce underfoot.

If joist spacing is too wide, deck boards will flex and feel unstable. The lack of underneath support can also cause warping or rot over time as boards get wet.

To avoid this mistake:

• Follow recommended joist spacing based on board thickness.
• For 5/4 boards, space joists 12" on-center. For 2x material, space 16" on-center.
• Reduce spacing by 2" if installing boards diagonally.

With properly spaced joists, your deck boards will feel solid underfoot and avoid damage from insufficient support.

Using the Wrong Fasteners

Choosing compatible fasteners is key for a durable deck build. The wrong fasteners can corrode, cause boards to loosen, or lead to cracking and splintering around the holes.

Using improper fasteners with pressure treated wood can also lead to moisture damage under the surface. This accelerates rot and decay.

Here are some fastener tips:

• Use screws and nails rated for treated lumber, like stainless steel or coated fasteners.
• Pre-drill holes near board ends to prevent splitting.
• Double up joists under board ends for added reinforcement.

With compatible, corrosion-resistant fasteners, your deck will maintain structural integrity for decades.

Not Sealing Properly After Installation

While pressure treated lumber is protected from insects and decay, sealing your deck properly is still essential for longevity. Quality wood sealants protect against surface cracking, inhibit mold growth, and reduce moisture damage from rainfall and snow.

Without sealing, pressure treated boards will weather to an unattractive gray and develop surface stains more rapidly.

Here are some sealing tips:

• Apply water-repellent sealant within several weeks of installing your deck.
• Re-apply sealant every 1-2 years for optimal protection.
• Carefully follow manufacturer instructions for application and drying time.

With proper prep work and regular sealing, a pressure treated deck will maintain its beauty for decades of backyard enjoyment.

Pressure treated lumber provides an attractive, durable choice for deck boards. But improper installation can lead to ongoing issues with cracking, warping, and decay.

By avoiding common mistakes like failing to pre-dry boards, improper spacing, incorrect joist layout, inferior fasteners, and lack of sealing, you can build a deck that withstands the elements and stays solid underfoot for years.

Take the time to thoroughly prepare pressure treated boards and use proper materials and techniques throughout the installation process. With careful deck construction, your family can enjoy decades of summertime barbeques, parties, and relaxing on a durable, low-maintenance deck.