Understanding Cumaru's Natural Character
Cumaru is a tropical hardwood known for its density, strength, and natural resistance to decay, insects, and weather changes. When freshly milled, Cumaru typically displays a rich, reddish-brown color with a distinctive grain. This natural coloration is part of its appeal for many homeowners.
As an untreated exterior wood, Cumaru will undergo a natural weathering process. Exposure to sunlight, rain, and environmental factors will gradually change its color. This process typically leads to the wood developing a soft, silver-gray patina over time. Some refer to this as 'silvering' or 'greying out.' This weathered look is often desired for its low-maintenance appeal and ability to blend seamlessly with natural landscapes or modern architectural styles. It's important to note that this color change is superficial and does not compromise the wood's structural integrity or durability, which is rated for over 25 years.
The timeline for Cumaru to fully silver can vary depending on local climate conditions, sun exposure, and initial treatment, if any. Generally, significant color change can be observed within a few months to a year.
Option 1: Embracing the Natural Silver Patina
Choosing to let your Cumaru decking weather naturally to a silver-gray is often considered the lowest maintenance option in terms of color preservation. This approach celebrates the wood's natural aging process and requires less frequent intervention to maintain its appearance.
The primary 'maintenance' for a naturally weathered Cumaru deck involves regular cleaning to remove dirt, debris, and any mildew that may accumulate. This helps prevent staining and keeps the surface safe for use. No oils, stains, or sealers are needed to maintain the silver color, as the natural process is allowed to occur unimpeded. This can be an attractive choice for those seeking a durable, long-lasting deck with a relaxed, understated aesthetic.
Option 2: Preserving the Original Color with UV Inhibitors
If you prefer to maintain Cumaru's original rich, reddish-brown hues, you will need to apply a finish designed to protect against UV radiation. Ultraviolet (UV) light from the sun is the primary cause of the wood's color fading and eventual silvering.
To preserve the color, a high-quality exterior oil finish with UV inhibitors is typically recommended. These products penetrate the wood, enhancing its natural color while offering protection from the sun's rays. The application typically needs to be repeated periodically, often annually or bi-annually, depending on the product, exposure, and wear. Regular reapplication is crucial; skipping treatments will allow the wood to begin its natural weathering process.
When selecting a finish, look for products specifically formulated for dense tropical hardwoods like Cumaru. Some products may be thicker or contain pigments that alter the wood's natural tone. Always perform a small test application on an inconspicuous area or a scrap piece of wood to ensure the desired color and appearance before applying to the entire deck.
Considerations for Factory Surfaces and Profiles
Cumaru decking is available in various profiles, such as 1"x6" (actual 3/4" x 5.5") and 5/4"x6" (actual 1" x 5.5"). The milling process leaves a smooth surface on the boards. While the profile does not directly dictate the finish appearance, it can influence how finishes are absorbed and how the surface feels underfoot.
Ensure that any chosen finish is compatible with the surface texture of the Cumaru boards. Some finishes may perform differently on smooth versus grooved or textured surfaces, though Cumaru is typically supplied with a smooth, planed finish. Always review the manufacturer's instructions for the specific finish product and Cumaru decking to ensure proper application and expected results.
Worked Example: Planning Finish for a 12x16-foot Cumaru Deck
Consider a hypothetical 12-foot by 16-foot Cumaru deck. This deck will be exposed to full sun for most of the day.
Option A: Natural Silvering. The homeowner desires a low-maintenance, weathered aesthetic. They plan to install the Cumaru 1"x6" decking and allow it to naturally turn silver. Their maintenance plan will focus on quarterly sweeping and an annual cleaning with a deck brush and mild, wood-safe cleaner to remove any accumulated dirt or organic matter. No staining or oiling is planned.
Option B: Color Preservation. The homeowner wants to maintain Cumaru's rich reddish-brown color. They choose to apply a clear, UV-inhibiting hardwood deck oil immediately after installation, once the wood has acclimated. Based on the product's recommendations and the deck's sun exposure, they budget for reapplication every 12-18 months. They will purchase enough oil for the initial application and one reapplication, storing any leftover product as directed. They also plan for regular cleaning between oiling cycles.
Before you order
- Do I prefer the natural silver-gray patina or the original reddish-brown color of Cumaru?
- Am I prepared for the ongoing maintenance (reapplication of oil/stain) required to preserve the original color?
- What is the level of sun exposure for my deck? (High sun exposure accelerates silvering and requires more frequent reapplication of UV-inhibiting finishes.)
- Have I reviewed specific finish product instructions for compatibility with dense tropical hardwoods like Cumaru?
- Do I have a plan for regular cleaning, regardless of the chosen finish appearance?
- Have I considered the aesthetic impact of a weathered vs. maintained appearance on my overall outdoor design?
- Will adjacent materials or landscaping complement the chosen Cumaru decking finish?
Confirm installation details, approved uses and warranty terms in the current instructions for the exact product and profile. Your installer should verify the substrate, structure and applicable project requirements.
Questions to help you decide
Does Cumaru's strength or durability change if it turns silver?
No. The silvering of Cumaru is a superficial change to the wood's color due to UV exposure and weathering. It does not affect the inherent strength, hardness, or natural resistance to decay, insects, or rot that Cumaru is known for.
What kind of oil should I use to maintain Cumaru's color?
To maintain Cumaru's original color, you should use an exterior hardwood deck oil specifically formulated with UV inhibitors. These products are designed to penetrate dense tropical hardwoods and offer protection against the sun's rays that cause fading. Always check the product's label for compatibility with Cumaru or similar dense hardwoods and follow the manufacturer's application instructions.
How often do I need to reapply a finish to keep Cumaru from silvering?
The frequency of reapplication for a UV-inhibiting finish depends on the specific product used, the level of sun exposure your deck receives, and local climate conditions. Generally, reapplication is recommended every 6 to 18 months. High sun exposure will typically require more frequent reapplication. Always refer to the finish manufacturer's guidelines for recommended reapplication schedules.
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