KAYU Hardwood Decking Installation Essentials – Sapphire

Storage and Handling

Kayu Decking Installation Essentials left facing deck with lake in background

  • Keep your KAYU® hardwood deck boards clean, dry and out of direct sunlight before installation and finishing.


  • Seal decking with a high quality penetrating oil sealer on all four sides prior to installation. Sealing only one side can create uneven moisture flow which increases likelihood of cupping.
  • A periodic light coat of finish will be required in order to maintain original color.
  • If you desire a weathered, silver grey look, leave all four sides unfinished and allow to weather naturally over time.

Ventilation and Air Flow

    • Check and follow your local building codes.

Kayu table and illustration showing Maximum Allowable Decking Spans

  • Allow adequate ventilation for proper air flow to reduce the potential for cupping and surface checking. (see diagram)
  • For maximum long term stability, install deck with a minimum ground clearance of 18”, with at least two sides of the deck open. It is absolutely necessary to have at least 50% unrestricted airflow.
  • Create a slope for drainage so there is zero chance of standing water.
  • If a minimum ground clearance of 18” is not available, we recommend 5/4 X 4 decking.


  • KAYU® decking is kiln dried. Unlike air dried boards shrinkage is very limited. However, excessive moisture may cause the boards to expand slightly.
  • Install 6” (5-1/2” net) decking with a minimum gap of ¼” between each deck board. 4” (3-1/2” net) decking should have a minimum gap of 3/16” between each board. Also allow ¼” from any
    structures such as foundations or rail posts.
  • In more demanding applications, such as boat docks, decks built closer to the ground and decks with less airflow, a minimum gap of 5/16” for 6” decking and a minimum of ¼” for 4” is required.
  • KAYU® decking does not shrink or expand end-to-end, so neatly trim ends and butt together.


  • Pre-drill pilot holes and countersink for all screws using high quality #10 or greater, stainless steel screws.
  • There should be a minimum screw penetration into joist of 1-1/2”.
  • Face screwing or edge screwing are the most effective methods of installation. Do not use hidden clip fasteners or nails!


  • Though we have had no reports of irritation of any kind with our hardwoods, we still recommend wearing protective eyewear, dust masks, and gloves during installation.


KAYU hardwood decking products are carefully selected and inspected to ensure the finest quality.  However, all natural wood is subject to expansion and contraction as the moisture in the environment surrounding the wood changes. Shrinkage, expansion, checking, slight cupping and other movement are normal occurrences in all hardwood decking.  Natural wood products are subject to variances in color, grain, density and performance.