A Guide to Cumaru Decking: Pros, Cons, Maintenance and Costs

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cumaru decking

Hardwoods and ironwoods are great for making specific things.

You can turn ironwoods to make long lasting handles, knobs, chairs and desks. Of course, you can always make planks and have near-lifetime flooring, or, you guessed it, a deck.

While ironwoods, like Cumaru, are hard to cut and almost impossible to nail through, they make a great deck for many reasons.

This article will examine Cumaru decking and find out if it is something you should look into further.

With Cumaru, also called Brazilian Teak, you get an affordable, rich colored wood that can stand the test of time. However, it isn’t for everyone.

Let’s find out if Cumaru is a good fit for you and your decking needs.

Top Reasons to Choose Cumaru Wood for Decking

There are a lot of wood options for decks and patios out there. Why should you use Cumaru? Here are the top reasons.

  • Hardy wood. Cumaru has a high Janka score and will last through all elements and for many years.
  • Inexpensive. Brazilian Teak is much cheaper than other hardwoods such as Red Oak and actual Teak.
  • Pest resistant. Cumaru is too dense and hard for termites and other wood boring pests to get into. This natural defense helps minimize your maintenance routine.
  • Fades naturally. Like other Brazilian ironwoods, the deep red coloring is beautiful, but naturally fades to an equally gorgeous silver color.
  • Rot and disease resistant. Ironwoods are less susceptible to rotting, cracking and splitting due to moisture and weather, making it ideal for outdoor decking.

What is Cumaru?

what is cumaru

Cumaru, better known by its nickname Brazilian Teak, is an ironwood that grows in northern South America. The tree grows to about 130 to 160 feet and produces a deep red or maroon wood plank.

While the wood isn’t as hard as it’s country sharing Ipe, Cumaru still has a Janka hardness factor of about 3300. This makes it about 7 times harder than redwood.

Cumaru has a hard core that makes it near impervious to termites and wood-borer insects. They simply don’t have the strength to bite it. It is also resilient to molds, weather damage, rot and decay.

As a decking material, Cumaru is difficult to install, which can raise deck install prices, but once the deck is complete, it will last as long, if not longer, than the house it is built next to.

Because it is a managed wood, meaning it is sourced from farms and selectively harvested, the wood is much cheaper than hardwood counterparts and premium woods.

It also comes in well under the cost of composite decking and aluminum decking, both of which last about as long and don’t look as natural and rich.

Pros and Cons of Cumaru Decking

While it may seem that Cumaru is an ideal decking solution (and for the most part it is), there are some downsides that you must accept when taking the good points. Let’s take a look at both sides of the coin now.

Advantages

Cumaru is found in some of the most well known places of the country, like the boardwalk at Coney Island. There are plenty of reasons why.

  • Extreme durability. When installed and weathered properly, Cumaru will stand the test of time and always hold up to whatever you can throw at it.
  • Rated for indoor and outdoor use. With a  USDA Forestry Service rating of 25 – very good, Cumaru can be used outdoors or indoors with minimal treatments.
  • Pest resistant. Bugs, insects and termites can’t bore through the ironwood, making it extremely resistant to insect damage.
  • Rot resistance. As an ironwood, even laying directly on the ground will not cause decay or rot for at least a decade. Off the ground, though, rot will virtually never occur.
  • High Janka rating. The Janka scale tests the hardness of woods, and Cumaru rates at 3300, which is about 7 times harder than Red Oak (1220 Janka hardness).
  • Higher than average slip resistance. When installed properly, Cumaru exceeds the Americans with Disabilities Act with a high static coefficient in wet environments rating.

Disadvantages

With the good, so there must also be bad. While the downsides aren’t too much to handle, some will find them to be a deal breaker.

  • Annual treatments needed. Cumaru should be treated with a UV coating every year for the first 4 or 5 years. This prevents splintering and cracking from weather and sunlight. After the 5th year, you can let the wood naturally fade to a silver tone, or maintain finish and UV coatings.
  • Difficult to cut. Cumaru is extremely hard to cut and requires expert use with a carbide tipped saw.
  • Not always available. While you can find Cumaru in almost any lumber yard and some home improvement stores, finding the “premium” or higher rated planks can be more difficult.
  • No nails or screws. Unlike other decking woods, Cumaru is an ironwood and must be predrilled. Even specialty screws and nails will bend and break without going through the wood.
  • Shrinkage and movement. As one of the lighter ironwoods, Cumaru is susceptible to seasonal movement and shrinkage more than other options.

Cumaru Decking Prices

cumaru decking costs

Brazilian Teak is a great decking material, and it is fairly inexpensive. It is far cheaper than actual Teak and will stand up a lot longer than most “normal” deck woods.

The actual cost of your project will have a lot of variables. These will include things like, size of the project, quality of the lumber, number of joists, foundation, layout, design and even the length and width of the wood.

Cumaru is similar to Ipe decking costs, which Home Advisor suggests is about $4 and $8 per linear foot. Premium Cumaru, though, will range between $4 and $12 per linear foot when purchased at a lumber yard.

This means that an average deck size of 150 square feet (10 x 15) will cost you between $4,000 and $9,500, with all materials and labor included.

How to Install Cumaru Decking

Before you open your wallet and start buying Cumaru boards, you need to decide a few things about the install.

First thing is to determine if this is a project you want to take on yourself, or if you want to hire out a professional for the task.

If you decide to hire out the project, finding a professional contractor that can handle the job is no easy task. We can help make the process easier. Just visit our Professional Contractor Locator.

You will get several contractor contact options for local options that are well reviewed and affordable. All you need to do is set up the estimate/quote visits to get your quotes.

For DIY install, there are several steps, again, similar to an Ipe wood deck process. There are a few small differences, though.
  • Approval and permits. Some areas require permits before you can add on to your home. Ensure you have the approval and permits needed for the project.
  • Acclimate your wood. Cumaru needs longer to acclimate than many other woods. Depending on where it was harvested and when it shipped, the entire acclimation process can last several months. Shop for premium labeled wood to minimize acclimation time, which should last at least 72 hours. An entire week is recommended, though.
  • Space the joists. Depending on the joist board size you will need to space your joists accordingly. 16 inches for 1×4 boards, 24 inches for 5/6×6 boards and 32 inches for 2×6 boards are average.
  • Double check the pitch or the area. You should have at least 1/4-inch pitch away from the home for every 10-feet out.
  • Cutting and sealing. Every time you cut a Cumaru board, you need to seal the cut ends with an end sealant. Note this is not the same as board sealer and should never be used on the top surfaces of the boards, only the cut ends.
  • Install the boards, leaving a proper gap and moisture lift (at least 18-inches at the joists) when placing the boards.
  • Screws or hidden fasteners. Decide if you will screw the boards or use a hidden fastener system to secure the Cumaru to the frame and joists. Predrilling for screw holes is required.
  • Finish. Cumaru, unlike Ipe, needs to be UV treated for the first 4 years at minimum. Once the deck is complete, apply your first coat of sealer and allow it to dry completely before use.

Cleaning and Maintenance

When it comes to preserving your new deck and keeping it looking great, Cumaru is about average on the maintenance scale.

Because it does need to be treated each year, there is a bit more work involved with some other ironwood decking options. Each year you need to do a few things to maintain the deck.

  • Check fasteners for seasonal movement. As the boards expand and contract during the different seasons, the screws and fasteners can begin to come loose. An annual inspection will keep the boards secure.
  • Apply UV protecting sealant. For at least the first four years you will need to apply an annual coat of UV sealant. After the 5th year, you can continue to apply the sealant, or allow the wood to begin its natural fading to a silvery finish.
  • Wash the decking. You can use a power washer or just a garden hose with a scrubbing brush. You will want to remove any built up debris, sap areas or dirt. Keeping the surface areas cleaned in this manner will prolong the life of the boards and your deck overall.

Aside from these maintenance aspects, there isn’t much else to do. You should sweep the deck on a regular basis. Keeping leaves, pine needles and other debris off the deck will keep moisture from staying and causing staining, water damage or dark spots.

Cumaru Vs. Ipe

Cumaru and Ipe woods have a lot of similarities. They are both ironwoods from northern South America. Each one is rated high on the Janka scale and each one fades to a beautiful silver finish after a few years.

Ipe decking, however, is more common in the decking industry. It has a higher source rate and is more readily available. Also, unlike Cumaru, Ipe wood doesn’t need to be UV treated right from the jump. You can, of course, and prevent the fading, maintaining the natural deep red coloring of the Ipe.

If you let Ipe fade, which is a popular choice, your annual maintenance drops to virtually zero, only requiring sweeping and an occasional hosing off to prevent staining or moisture accumulation.

Ipe is also slightly cheaper, but because it is more available, less than premium quality wood is also out there. You need to ensure that when buying either Ipe or Cumaru that you purchase only premium rated or higher planks.

Both also require a 72 hour to 7-day acclimation period. This helps minimize expansion and seasonal movement.

Since both ironwoods are similar, even down to the color and fading, it can be difficult to tell them apart.

There are two ways, though.

Cumaru has a faint odor or vanilla and cinnamon when being cut and the heartwood fluoresces under a black light. Ipe also has an odor, but it’s more of a mild grassy/nature odor and the heartwood does not fluoresce.

Known Issues When Using Cumaru (and Their Solutions)

cumaru known issues

As an ironwood, there are some obvious (and not-so-obvious) issues when working the wood. Luckily there are simple solutions to these problems.

Let’s take a look.

Expansion and Movement

Cumaru needs time to acclimate to it’s final climate and humidity levels. Like other ironwoods, there is more movement during the seasons than with other hardwoods.

Depending on your climate, you may experience more movement than in others.

Because Cumaru is native to hotter, more humid climates, installing the wood as a decking in colder, drier climates will result in more movement. While this is normal, there is still a chance for some larger gaps between planks when the temperatures drop significantly.

Solution: Acclimation and moisture prevention. Having a concrete slab under the deck, improper draining and not enough acclimation time will cause more movement.

For best results you shouldn’t build your deck over a concrete slab and make sure you allow at least 72 hours of acclimation before building. In colder or drier climates, acclimating the wood for up to a week is recommended.

Spotting and Staining

As with most ironwoods, stains come in the form of dark spots or blotches. Known as spotting, this is the result of stains from grease, water or sap. If left uncleaned,

Cumaru can develop dark spots when moisture or grease is left to set on the surface.

During the first few years, when using a UV sealant, this is less prevalent, because the sealant will protect the wood surface from moisture retention.

However, if you have decided to let the wood fade to a natural silver finish, once you stop using the sealer, spots can develop.

Solution: Continue to use sealants and maintain the rich red wood color. If this is not your desire, you will need to become more proactive about allowing leaves, pine needles and other debris from setting on the wood for too long.

Moisture retention is the leading cause for spotting. Clean up any debris as soon as you can, and if your barbecue splatters or you drop grease and food debris, clean up immediately.

Cutting and Installing

Cumaru is notorious for being difficult to work. Like most ironwoods you must use a carbide tipped saw blade to get a smooth even cut. Other blade types will dull quickly, splinter the wood or cause burnishing.

The wood is also highly difficult to nail or screw because it is so dense. Nails will bend and screws will snap in half. This can make installation a long, tedious process.

Solution: Opt for predrilled boards, or drill the pilot holes for the screws yourself. It may cost more, or take longer to finish the install, but the frustration levels will drop, making it worth the extra time.

When cutting your boards, use a carbide tipped saw blade and change when the cutting becomes too slow or sticks. You will also need to use end sealer on the cut edges to prevent leaking or moisture absorption.

Frequently Asked Questions

faqs cumaru decking

In this section we will cover the more commonly asked questions about Cumaru and ironwood decking. As always, if you have more questions, feel free to use the comment section below.

Q. How long do Cumaru decks last?

  1. A well maintained and properly installed Cumaru deck can last many years. On average you should expect about 25 to 30 years before considering replacement. However, many decks and walkways have been used for decades without much need for repair. When replacing only broken or splintered boards, your deck can easily reach 40 years or more.

Q. Why is Cumaru called Brazilian Teak?

  1. The name Brazilian Teak is just a moniker given the wood to help raise it’s value. Many woods do this, including Rhodesian Teak. However, unlike many other wood types with the Teak nickname, Cumaru does have many of the same characteristics and look. Cumaru is also known as Tonka Bean, Tonka and Golden Teak.

Q. What kind of hardware is required for Cumaru decking?

  1. When building your Cumaru deck along with a carbide tipped blade, you will need to use stainless steel 305 screws (or higher rated) to ensure movement doesn’t cause loosening over time. This will also make sure the screw threads dig in and get a grip instead of dulling as they turn.

Q. Does Cumaru require sanding?

  1. Yes, when installing, finishing and refinishing you need to lightly sand Cumaru. Using electric sanders is recommended, though you should go slow. Like other ironwoods, Cumaru can easily burnish, leaving burnt marks and discoloration. Sanding will remove old surface treatments and prep the wood for a new coat.

Conclusion

Cumaru, or Brazilian Teak, is an ironwood that comes from the northern South American forests. It is a naturally sustained wood and is not listed on any endangered lists.

It is also extremely durable, rated for both indoor and outdoor use and has a rich, deep coloring.

As a decking material, Cumaru can be difficult to work with. Because it is so hard, it is termite and borer-insect resistant and also staves off rot and decay for decades.

When left to fade naturally, the deep red color slowly turns to a silvery gray, making for a beautiful finish over the course of its life.

You can find Cumaru as the decking at Coney Island which has been allowed to naturally fade to silver and is still holding up well over many years and extremely high traffic.

As an endorsement for durability, it doesn’t get much better than that.

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AUTHOR

Nora has more than 5 years experience in the floor covering industry, acquiring vast knowledge about installation and material selection. She now enjoys working as a writer and an interior decorator. Her work has been featured in The Spruce, Homes & Gardens, Southern Living and Real Homes. See full biography here.

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