The best policy is to always follow correct practices to ensure a project's success. The primary reason a hardwood deck usually fails is due to INCORRECT INSTALLATION.
There are a number of critical steps that a homeowner or builder should follow in order to ensure a deck is correctly and successfully installed...
Width of material
- Build your deck so that the surface is at least 16” above the ground when using 1x4 or 5/4x4 decking material.
- When using 1x6 or 5/4x6, the deck must be constructed a minimum of 36” off the ground.
Ventilation / Air Flow
- There must be adequate air circulation underneath the deck in order to prevent cupping and warping of boards.
- When designing your deck, ensure you provide a minimum 50% open space below your deck for proper ventialtion
- In close to ground applications, 60” or less above ground, a vapor barrier and pea gravel is necessary to inhibit the possibility of water pooling and allowing moisture to absorb into the underside of the decking boards.
- You must allow space for your deck boards to expand when they take on moisture, as they will inevitably do when exposed to wet weather, rain or high humidity.
- The final spacing should be at 1/4” if you have kiln dried material with a moisture content in the 10-12% range and relative humidity in the 35-45% range. If you are installing during very dry conditions and the boards are measuring in the 6-8% range, then you should add 1/16” additional spacing so that your deck can handle higher humidity and rain.
- If you are installing Air Dried Decking (such as Ipe) with a high moisture content in the 16-18% range, a spacing between boards of 3/16” is appropriate to ensure that the material does not gap too much in dry weather.
- There is a specific science behind the required gap which is a function of the exact wood species, the beginning moisture content of the wood and the dry and wet extremes you want your deck to handle. In most cases, you should plan for 100% humidity levels and expect that the deck boards will expand to their maximum amount at the fiber saturation point of the wood. The dry side of the equation has more variability since many areas of the country have typical minimum humidity levels. You don’t need to plan for bone dry conditions in the Southeastern United States, for example; but you certainly do need to plan for bone dry conditions in Arizona and Central California.
- Several different options are available for fasteners and for fastening techniques. We recommend stainless steel screws through the face of every board, two screws per joist.
- Self-tapping stainless steel screws are available but may require pre-drilling.
- Pre-drilling is always required on the ends of the boards.
- We do not recommend the use of nonstainless fasteners since they will cause discoloration near the fastener. Do not use carbon-steel screws.
- Do not use deck clips, hidden fasteners, or any other mechanical fastening systems, including those which fasten from the underside or edges of the boards. Despite manufacturers’ claims, we have determined that these products do not provide adequate anchoring of hardwood deck boards to the substructure.
We require that the boards are end-sealed as soon as reasonably possible after cutting during installation.
A clear, water-resistant wax should be used. One such product is Anchorseal from UC Coatings, although several other products are available.
Weatherizing & Sealing / Finishing
Especially in dry, sunny conditions, finishing must be done prior to exposure to weather. Finishing Nova Decking on the underside of your deck will reduce potential cupping by inhibiting moisture from absorbing into the wood.
For best results, apply the treatment according to the manufacturer’s directions. To maintain the natural color, a high quality penetrating oil finish with UV inhibitors should be used.
The only reason a hardwood deck fails when close to the ground is INCORRECT INSTALLATION. Nova’s warranty is against rot and decay - it does not cover shrinkage and expansion.
For additional information regarding best installation practices visit our website https://www.novausawood.com/decking-installation-guide.aspx
If you need further information please do not hesitate to call the experts at Nova for assistance.