Cumaru Installation Instructions
Handling & Storage - Like Massaranduba, Cumaru is dried from 12 to 20% moisture content. As the material adjusts to local weather conditions, it will expand in width about 1/8" if the moisture content is closer to 12%; or, if the moisture content is closer to 20%, it will shrink about 1/8". Acclimate this material to current humidity levels before installation by storing in a cool, dry place, out of direct sunlight.
Installation - Design your deck to stand at least 24" above the ground and be open on at least 3 sides to promote adequate cross ventilation. 1x6 Cumaru decking may be installed on 16" o/c. joist systems. 5/4 material also may be installed on 24" o/c. Installing decks with a diagonal pattern may require narrower joist spacing. When installing, allow a minimum 1/4" space between 6" planks. This promotes air circulation, allows drainage, and leaves room between the boards for shrinkage and expansion. The average rate of shrinkage is approximately 3/16" on 6" wide boards.
Cutting - Carbide-tipped saw blades and drill bits are recommended when cutting. When drilling, bore pilot holes close to the actual screw or nail diameter. If using trim-head screws, it is recommended that you drill a slightly larger hole than the diameter of the screw head so it can countersink itself.
End Sealing - The ends of the Cumaru boards are end-waxed. Any cuts made on the planks must be immediately resealed with a clear aqueous wax end sealer to help reduce checking. We recommend "Anchorseal" by UC Coatings.
Fastening - Stainless steel fasteners are recommended because of superior corrosion resistance, maximum holding power, and ease of use. Always pre-drill a pilot hole before driving screw fasteners in any application and countersink screw fasteners when face screwing deck boards. There are also various hidden-type, under-mount or clip systems, that may be used without causing unsightly surface punctures; and, eliminate the potential for water to pool or stand on the surface, leading to wood rot and deck failure. The DECKMASTER® hidden deck fastening system is a great example. Make sure you buy the appropriate size DECKMASTER® bracket for the deck boards you are installing, pre-drill and ask us for more information!
Finishing - After finishing your deck, clean the surface and wait at least 2 days to apply a thin coating of high quality penetrating oil-based sealer with UV inhibitors that limit checking and color fading. It is recommended that you test any product chosen on several sample boards to determine compatibility.
We recommend applying a quality penetrating oil finish with a UV sun block after completing your deck. U.V. Plus by Messmer's or Penofin's Bronze Label Hardwood Formula finish are excellent products that will keep your wood looking its best. Within 3-6 months, follow up by applying another coat or when your deck looks dry or weathered. These initial applications help saturate the wood fibers, adding protection to preserve your deck and make "maintenance" coats less frequent. Over time, apply this finish periodically to maintain the natural color. If you prefer, Cumaru will weather naturally without any oil to a silver gray patina over a period of time, thereby eliminating any finish maintenance. We do recommend that you at least apply an initial oil finish to your deck after completion and seasoning. Please call us with any questions.


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