Jatoba vs Ipe: Comparing Stiffness and Stability.
In Part 1, we looked at 2 key factors in comparing Jatoba with Ipe in order to evaluate how good of an alternative it is for decking. While hardness and weight certainly bear consideration, so do stiffness and stability, unless you want unreliable performance — or a bounce house. But if you intend to build a deck, we’re pretty sure neither is the case.
To use a more technical term, stiffness can be referred to as the Modus of Elasticity, or MOE. Measured in pounds per square inch, this aspect of a species describes how much the boards flex underfoot between supporting joists. When you look at the numbers, Ipe outranks Jatoba by about 15%.
What does that mean, practically? Not much. Jatoba has an MOE that allows it to lack bounce as long as centers are installed every 16 inches. Ipe could technically use 24” supports and still have no bounce; however, 16” has become industry standard, so it really doesn’t make a difference. In fact, some deck builders even push for 12” spacing — possibly as an outgrowth of working with softwood decking that can develop bounce with 16” centers. So is Ipe stiffer than Jatoba? Sure. Does it really matter? No.
News flash: wood moves. It’s an organic material, and, as such, it is far from static. We can’t stop how wood moves, but we can understand it, plan for it, and work with it. The way wood moves can be described as anisotropic, meaning that it moves in unequal ways, instead of the same in every direction (which would be described as isotropic). As you look at the growth rings of a piece of wood, the movement will move significantly more in ways parallel to the growth rings (tangentially) than perpendicular to them (radially). A wood’s stability can be figured based on the difference between the percentages of tangential and radial movement.
Ipe has movement that can be described as 8% tangential and 7% radial, while Jatoba is 7.1% tangential and 3.8% radial. As a result, Ipe has a 1.1 ratio of tangential-to-radial movement, to Jatoba’s 1.9 ratio. Basically, Ipe is as close to isotropic as wood can get. Its amazing stability certainly makes it easy to plan for and work with. With decking lumber, one reason stability can be an issue is the way the two main faces of a board can have completely different moisture content. While the top can be completely dry, as it bakes in the sun all day, the bottom can remain damp. This situation can cause the board to cup within the same grain plane; of course, the percentage of movement cannot account for the likelihood of that.
This is where Jatoba wins out. Even though Ipe appears more stable on paper, Jatoba actually exhibits less cupping out there in a real deck situation because of its slightly lower density. The small amount of extra empty space between the cells lends elasticity, which prevents the cupping.
In Part 3, we’ll discuss the way all this information comes together and what it means for Jatoba as an Ipe alternative.
While no wood species will have exactly the same set of characteristics that makes Ipe such an ideal wood, certain species may offer comparable strengths, making them possible Ipe-substitutes depending on your particular project and environment. Learn about each Ipe alternative below: