How to Install Cumaru Decking
Get a step-by-step installation guide tailored to your exact project.
What type of project is this?
Application Type
Residential
Single-family home or personal use
Commercial
Business or public use
Complete Cumaru Decking Installation Guide
Cumaru (Dipteryx odorata) is a premium South American hardwood offering exceptional durability, natural resistance to rot and insects, and beautiful golden-brown coloring. With a Janka hardness of 3,540 lbf — actually harder than Ipe — Cumaru provides outstanding value for high-performance outdoor decking at a more accessible price point.
Janka Hardness
3,540 lbf
Density
64 lbs/ft³
Expected Lifespan
25+ years
Origin
Brazil, Peru, Venezuela
Step 1: Acclimation & Storage
Stack Cumaru boards with spacers in a covered, ventilated area for 5-10 days depending on climate. Keep boards off the ground on pallets or blocking. Cover with a tarp but leave all sides open for air circulation. Never wrap in plastic. Check for damage and verify species upon delivery — Cumaru color ranges from golden-brown to reddish-brown.
Step 2: Framing & Substructure
Use pressure-treated joists at maximum 16" on center (12" O.C. for diagonal patterns). Apply joist tape to all joist tops to prevent moisture issues. Ensure 18"+ clearance underneath for ventilation. Install blocking between joists at board ends for added stability. Cumaru's weight requires robust framing similar to Ipe.
Step 3: Board Layout & Spacing
Separate boards into color groups (light, medium, dark) and mix them evenly across the deck for balanced appearance. Side gaps should be 3/16" to 1/4" and end gaps 1/4" to 3/8", adjusted for your climate zone. Stagger end joints by at least 2 joists and place best-looking boards in high-visibility areas.
Step 4: Pre-Drilling & Fastening
Pre-drilling is mandatory for every fastener hole — Cumaru will split without it. Use stainless steel fasteners exclusively. Options include hidden clip systems, face-screwing with trim-head screws (#8 x 2.5"), or face-screwing with Cumaru wood plugs. For hidden fasteners, buy 10% extra clips as some may break during installation.
Step 5: Cutting & End-Sealing
Use a carbide-tipped blade with 60+ teeth for clean cuts. Cut slowly — forcing through dense Cumaru dulls blades quickly. Apply wax-based end grain sealer to ALL cut ends immediately, with 2-3 coats extending 1" onto the board face. Skipping end-sealing is the #1 cause of premature board failure in hardwood decks.
Step 6: Finishing
Cumaru can be oiled with penetrating hardwood oil to enhance its golden-brown color (wait 2-4 weeks after installation), sealed with a UV-protective sealer, or left to weather naturally to silver-gray over 6-18 months. Use only products formulated for exotic hardwoods — generic deck stains won't penetrate dense Cumaru properly.
Step 7: Ongoing Maintenance
Sweep regularly and clean 2-3 times per year with mild soap. If oiled, re-apply when water stops beading (typically annually). Cumaru requires minimal maintenance and provides 25+ years of durable service. Expect some natural surface checking — this is cosmetic and does not affect structural integrity.
Required Tools
- Miter saw with carbide blade (60+ teeth)
- Drill with carbide bits
- Impact driver
- Countersink bit
- Level
- Rubber mallet
- Spacers
Materials Needed
- Cumaru decking boards
- Stainless steel fasteners
- Joist tape
- End grain sealer
- Hidden fasteners or screws