To prevent separation at the miter joint when installing wet pressure-treated 5/4 x 6 deck boards for your top rails, follow these steps and tips:
Acclimation: Allow the deck boards to acclimate to the environment by storing them near the installation site for at least 48 hours before installation. This helps the boards adjust to the moisture level of their surroundings, reducing the potential for excessive shrinking or expansion after installation.
Pre-drilling: Before securing the miter joint with screws or nails, pre-drill pilot holes for the fasteners. This step helps prevent the wood from splitting when driving in the screws or nails.
Wood Condition: Check the condition of the deck boards before installation. Avoid using warped or severely cupped boards, as they may cause issues with the miter joint later on.
Fasteners: Use high-quality, weather-resistant fasteners suitable for pressure-treated wood. Stainless steel or coated deck screws are often recommended because they are less likely to corrode and cause the joint to weaken over time.
Construction Adhesive: Apply a construction adhesive specifically designed for outdoor use to the miter joint before fastening the boards together. This adhesive will create a strong bond between the two pieces and help prevent separation.
Gap: Leave a small gap between the ends of the deck boards at the miter joint. This allows for natural wood expansion due to changes in moisture content. A gap of approximately 1/8 inch should be sufficient.
Sealant or Water Repellant: Apply a water-repellant sealant or deck finish to the cut ends of the deck boards. This helps protect the exposed wood from moisture penetration, reducing the risk of swelling or warping.
Proper Installation: Ensure the miter joint is well aligned and tight before fastening the boards. Use clamps to hold the joint securely while inserting the screws or nails.
Screw or Nail Pattern: Use an appropriate screw or nail pattern to secure the miter joint. For screws, placing them in a staggered pattern can improve joint strength.
Regular Maintenance: After installation, regularly inspect and maintain your deck to ensure it stays in good condition. This includes checking for loose fasteners and making any necessary repairs promptly.
By following these steps and taking proper precautions, you can help prevent separation at the miter joint and increase the longevity of your deck's top rails.