Durability implies something that lasts a long time and will hold up to various climatic conditions as well as foot traffic. That requires consideration of the finish on the surface, in addition to the type of wood, glues, and moisture content as they affect the overall structure of the floor. You must also understand the subfloor, whether concrete or wood, and know how it impacts the flooring that sits on top of it.
It's not the wood, it's how it's made and installed
There are horror stories about both bamboo and hardwood floors that buckle and crack in hot dry climates, and these same complaints are often heard in very wet climates as well.
There’s nothing inherent about hardwood that makes it better than bamboo. Local hardwoods seem to work just as well as other domestic or imported hardwoods or bamboo; as long as they’re installed and acclimated correctly over a suitable subfloor. The issue is not what species it is, but how it’s made and how it’s installed.
For hot and dry environments
Our experience in hot or dry areas such as Arizona, Colorado or California is that floating engineered floors seem to work best for both bamboo and hardwood.
Floating means that it is not glued or nailed down but sits on top of an 1/8" underlayment along with a vapor barrier. This allows the floor to expand and contract as needed over a concrete or plywood subfloor uninhibited by nails or glue.
Engineered means that the floor has multiple layers of hard or soft wood, bamboo, high- density fiberboard (HDF) or some combinations of both. The purpose of multiple plys is additional strength and resistance to movement across the grain or with the grain of the wood. Excessive dryness or excessive moisture tends to exert pressure in various directions. If the wood is solid, for example, it tends to twist and turn according to the grain of the wood. If it is engineered, the cross-plys keep the plank from twisting and turning so easily. We've seen engineered floors subjected to extreme moisture and extreme dryness causing minor buckling, but when the moisture levels change, the floor relaxes back into its original shape. This does not happen as quickly or easily with solid wood floors.
Our favorite engineered harwood floor
Our favorite engineered hardwood floor is made by a Swedish company called Kahrs, which invented floating floors some 25 to 30 years ago. In Sweden, many people use radiant heat under their floors, and Kahrs designed its floors to accommodate infrared heat. Kahrs allowed for the natural contraction process by using quarter sawn wood, which is more stable than plain sliced wood in-between the top and bottom layers. Instead of one solid core of quarter-sawn wood, its broken into small fingers and separated with tiny gaps. As a result, the wood expands and contracts inside and not on the surface.
Kahrs, as well as other manufacturers such as EcoTimber, US Floors and EcoFusion (see these at Green Building Supply) have also been successful with HDF cores due to their extreme stability. However, there is much more to the story than just the core structure.
How an engineered floor is made is quite complex and involves many steps including the use of the right type of core material, drying and gluing the wood together in just the right sequence so that it maintains the right amount of moisture. If the surface is a dense hardwood, for example, then the core of pine or HDF as well as the wood on the bottom plane must be able to move in harmony with the hardwood on the surface. This is not as easy as it may seem. All types of glues have been used to control moisture and overcome the movement of each plane of the wood. Unfortunately, some of the adhesives used by hardwood and bamboo manufacturers are not safe.
To their credit, the Europeans seem to be bent on non-toxicity of their adhesives and their finishes. As a result, their products are safer than anywhere else. This applies to cork, Marmoleum, hardwoods, softwoods etc.
The latest trend in hardwood flooring coming from Europe is oiled finishes. These old-time proven finishes are not only non-toxic, but they tend to allow the floor to breathe easier, which means it can naturally adjust to the changes in climate. We’re now seeing these on both bamboo and hardwoods.
Most flooring today has a finish prepared with aluminum oxide or polyurethane, both of which are petroleum-based topical sealers that perform very well at resisting abrasion and moisture, but are expensive to apply and reapply years later. They also have an unnatural plastic look and feel. Oiled floors, on the other hand, are much more reparable, and can be reapplied easily and cheaply without professional experience. Oiled floors patina nicely over time, which tends to enhance the color and feeling of the wood/bamboo surface.