Ipe Decking vs. Cumaru Decking | Article Summary

This report compares Ipe Decking to Cumaru Decking; both species of wood are from South America, principally from Brazil, Peru, Bolivia and Guyana. Our objective is to show that Cumaru is a reasonable alternative to Ipe and is a great choice for your next residential decking or commercial decking project.

Cumaru Decking

Background on Ipe Decking, Ironwood, Brazilian Walnut

Ipe, Tabebuia spp., has been used since the 1950's in commercial and residential decking projects. Some very famous projects in the United States have featured Ipe Decking, for example: the Atlantic City, New Jersey boardwalk and the walkway in front of the Treasure Island Hotel in Las Vegas, Nevada.

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The Best Wood Decking Choice

Ipe is regarded as the best material possible for use as exterior decking. Ipe has earned its reputation because it is naturally durable, stable, resists checking, and is absolutely gorgeous. With a deep and rich red brown color, Ipe is considered by most lumber experts to be the ultimate choice for high quality decking.

Where Does It Come From? | Environmental Issues

Ipe grows throughout the tropical regions of South America and Central America. Like so many other exotic tropical hardwoods, Ipe is found in the rainforests regions of the Americas. The Brazilian rainforest which extends into Bolivia, Peru, Columbia, Venezuela, Equador and the Guyanas, is the most heterogeneous forest in the world; with more diversity of species, it is critical that we do not put too much pressure on any single species of timber. Ideally, we will find acceptable commerial uses for most of the species which flourish in the Amazon. By carefully harvesting our tropical forests, we can sustain this exceptional resource forever. The key is to use selective logging and not to clear cut the forest for agricultural uses. See our environmental page for more information.

Distribution Chain | Manufacturer to Importer to Distributor to Retailer

There are many importers of Ipe decking in the United States. We estimate the annual volume of Ipe decking imported into North America at approximately $100 million. Ipe is sold by importers to distributors, who in turn generally sell to retailers, and then finally to the general consumer. There are well over a hundred distributors in the United States that keep Ipe decking in inventory. You may also find some larger retailers who keep Ipe in stock - it is always best to find it in stock and avoid "special order" charges.

Some of the early pioneers in tropical hardwood decking include Timber Holdings and WG Moore and Sons; what started as mostly commercial business became more focused on residential decking during the last 15 years. Residential decking is by far the predominant use of Ipe in the U.S.

Grading | First Clear, #1, First Export Clear | Select, #2 Grade

90% of the Ipe imported into the U.S. is #1 Grade; this is the equivalent of First Clear, First Export Clear, and FAS. There is no official grade, but most manufacturers follow similar standards, grading for one side relatively defect-free. Minor defects such as small knots, bug holes up to 1/8" in diameter, light planer miss or tear out, and other non-structural defects are allowed on the back side. The #2 Grade is sometimes called "Select" and is still an excellent piece of wood for use as decking. You should expect to pay 20-30% less for a #2 Grade product.

Air Dried vs. Kiln Dried Material | Moisture Content and Equalization

Ipe is available in Air Dried (AD) and Kiln Dried (KD) formats. Air dried material is shipped on thin sticks or lathe and usually gets only a few weeks of open air dry time after cutting at the saw mill prior to surfacing to final decking sizes. The longer the amount of time prior to surfacing, the better the final product will be in terms of consistent sizing. Air dried decking will continue to dry en route from South America, and continue to lose moisture while in storage once it has arrived to the distributor's or importer's warehouse. The longer the material has been sitting in the warehouse, the more likely it will be properly equalized to the environmental conditions in that region.

Kiln Dried Ipe is not shipped on sticks or lathe. It is generally kiln dried to 10-12% MC or Moisture Content. The kiln drying process eliminates the sticker marks generally found every two feet with air dried material. Some distributors and importers will sand the air dried material to remove sticker marks; this is effective but will still result in some minor width variations between boards. Kiln dried material is pre-equalized and consistently sized. The most important issue with kiln dried material is to be sure you have adequate spacing between boards when installing - 1/4" gap between boards is recommended for 1x6 and 5/4x6 material and 3/16" is recommended for 1x4 and 5/4x4 material. See our installation guide for more information.

Cumaru Decking | Background Information

Cumaru hardwood was one of the first exotic wood alternatives to Ipe for use as decking. Imported from the same regions as Ipe, Cumaru is somewhat similar in appearance and was originally just mixed in with Ipe. Cumaru is often separated into two color separations: light, also known as standard Cumaru, Brazilian Teak; and dark, also known as Red Cumaru, Brazilian Chestnut, or Southern Chestnut.

Air Dried Cumaru Exhibits Checking

In the 1990's, when Cumaru first came onto the imported hardwood decking scene, most of the material was imported as Air Dried only. This caused major problems because Cumaru has more of a tendency to show checking than Ipe. It was relatively easy to distinguish the Cumaru from the Ipe, and Cumaru quickly received an unfair reputation as a poorly performing tropical decking wood. Of course, Cumaru was also cheaper than Ipe and hence companies were motivated to push the limits of acceptability.

Kiln Dried Cumaru to the Rescue

As companies realized the error of their ways, Cumaru was no longer mixed in with Ipe. And most companies today realize that Cumaru must be kiln dried in order to work properly as decking. In fact, kiln dried Cumaru is likely to be more stable and more consistent in size than air dried Ipe; and you won't get any sticker marks with kiln dried Cumaru. Cumaru should be kiln dried to a moisture content of 10-12% for best results.

The Cumaru Distribution Network

Cumaru decking is imported by many of the same companies as Ipe, although the volumes are probably only 5% to 10% of the $100 million per year Ipe decking market. Cumaru is also used for interior flooring, as is Ipe; and both offer beautiful grain and color characteristics. Cumaru decking is stocked by just a handful of distributors throughout the U.S. Few retailers stock Cumaru, but you should be able to find out where to buy it by calling or emailing Cumaru decking importers.

Long Term Supply of Cumaru Hardwood Lumber

Cumaru is readily available from many countries in South America. Long term supplies are plentiful and sustainable forestry practices apply just as they do with harvesting Ipe. There is less pressure on Cumaru trees and we certainly expect that Cumaru will have a long future as one of the primary tropical hardwood species used for residential and commercial decking.

Stength and Durability Characteristics of Typical Residential and Commercial Decking Woods

Below is a table comparing the various types of wood that are often used in residential and commercial exterior decking:

SPECIES Approximate Weight per MBF at 10% MC Modulus of Rupture (psi) Modulus of Elasticity (1000 psi) Maximum Crushing Strength (psi) Side Hardness (lbs) Shear (psi)
Ipe 6,400 25,400 3,140 13,010 3,680 2,060
Cumaru 6,300 24,800 3,050 12,200 3,200 1,980
Massaranduba 6,400 27,300 3,450 11,640 3,190 2,500
TigerWood 4,600 20,120 2,390 10,320 1,850 1,960
Purpleheart 4,800 21,300 2,420 11,380 2,060 1,830
Angelim Pedra 4,400 17,600 2,050 8,990 1,720 2,010
Southern Yellow Pine 3,100 14,200 1,880 7,750 750 1,490
California Redwood 2,600 7,900 1,100 5,220 420 1,110
Western Red Cedar 2,500 7,500 1,110 4,560 350 990

US Dept. of Agriculture Handbook No. 207
US Dept. of Agriculture Handbook No. 72, pp 4-24

When evaluating the suitability of a particular species, one must consider the various strength factors, the hardness and the weight of the specie.

Another important factor to consider is the stability of the wood species. Below is table comparing shrinkage from green lumber to 0% moisture content, or maximum shrinkage. Because wood does not shrink or expand uniformly, one should consider the difference between radial and perpendicular shrinkage; if the differential is high then the wood will be less stable.

Moisture Related Shrinkage, Expansion and Stability Characteristics

SPECIES Shrinkage Radial to Grain Shrinkage Perpendicular to Grain Differential Shrinkage Volumetric Shrinkage Stability Ranking
Ipe 6.6% 8.0% 1.4% 14.1% #3
Cumaru 5.4% 8.4% 3.0% 13.3% #8
Massaranduba 6.3% 9.4% 3.1% 15.1% #10
TigerWood 4.0% 7.6% 3.6% 11.3% #9
Garapa 6.5% 10.0% 3.5% 15.9% #13
Purpleheart 3.2% 6.1% 2.9% 9.1% #4
Angelim Pedra 4.4% 7.1% 2.7% 11.2% #5
Bankirai, Yellow Balau 4.5% 8.3% 3.8% 12.4% #11
Red Balau 4.8% 8.8% 4.0% 13.2% #12
Dark Red Meranti 3.4% 6.6% 3.2% 9.8% #7
Cambara 4.2% 9.1% 4.9% 12.9% #14
Southern Yellow Pine 4.8% 7.4% 2.6% 11.8% #6
California Redwood 2.2% 4.9% 2.7% 7.0% #2
Western Red Cedar 2.4% 5.0% 2.6% 7.3% #1

US Dept. of Agriculture Handbook No. 207
US Dept. of Agriculture Handbook No. 72, pp 3-15

Ranking system above is based on weighting the differential shrinkage amount by a factor of 4 and adding the volumetric shrinkage to the result. (i.e. 4x differential shrinkage + volumetric shrinkage).

As expected, Ipe is the most dimensionally stable specie of the hardwoods. The fact that it has such a low differential shrinkage between radial and tangential directions helps prevent the wood from twisting, cupping, and warping.

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