Like linoleum, cork flooring was more popular in the past than it is today, although it is making a comeback. Cork is not wood in the typical sense, but the bark of the cork-oak tree, Quercus suber. This is an evergreen tree that originated in the Mediterranean Sea area. Today, it’s still being cultivated in Spain and Portugal where it’s sometimes planted between olive groves and vineyards. Other cork-producing areas are in India and in the western U.S.
After about 20 years, a cork-oak tree is first ready to be harvested. This is done by stripping off the external bark. This does not kill the tree, since in about ten years, the tree will have grown a new bark covering that will again be ready for harvesting. Surprisingly, the cork quality seems to improve with each harvesting.
Once harvested, the cork bark sections are cleaned, boiled, and have their outermost layer (a very rough material) removed. Then bottle stoppers may be stamped out. What remains of the sections are then ground, mixed with some type of binder (either natural proteins or resins, or a natural or synthetic glue) which will allow it to keep its shape. Then the material is rolled, baked, and cut into lengths to create smaller rolls (for wall applications), or it can be molded into blocks, baked, and sliced into tiles for flooring. Newer cork-flooring variations include a tongue-and-groove product fabricated of a top cork layer glued over a man-made “pressboard” backing, and a vinyl-cork-hybrid tile.
Real cork flooring has a number of pluses. It’s a natural material that comes from a sustainable resource. Because the bark cells are hollow, airtight, yet flexible 14-sided structures, cork floors act as good insulators against cold and noise. Cork flooring is usually long lasting, naturally resists moisture and rot, and also has the ability to be stained like traditional wood. It should also be pointed out that cork floors are resilient (able to regain their original shape after being compressed). So, they are comfortable to walk on. Finally, cork flooring is easy to clean by vacuuming, sweeping, or washing (use only a minimal amount of water.)
However, there are negatives associated with cork floors. One of the most important is that, these days, cork flooring is quite expensive. Then, too, it will require the added work of applying a sealer and protective finish (e.g., polyurethane) unless already prefinished. Another concern is that cork flooring can acquire permanent stains. And while the cork bark is inherently waterproof, cork isn’t a good choice for places where it could come into contact with water, such as bathrooms, where moisture could eventually enter in the cracks between the tiles.
There are also potential outgassing problems. Some binders are fairly noxious; for example, urea-formaldehyde (UF) glue is used by some companies. Of course, if a mastic (a type of construction adhesive) is required to adhere the tiles, that could be a potential problem since conventional installers often use a solvent-based polyurethane-type product. Top finishes (e.g., polyurethanes) can be odorous too, although alternative products, some of which are water-based, are available.
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