Cork Puts a Bounce in Your Step

By Jeanne Huber
Special to The Washington Post
Thursday, June 15, 2006

Q I recently heard about using cork for flooring. Does it make sense?

A In many ways, cork could be considered the ideal flooring material: beautiful, durable, easy to care for, wonderful to walk on, and blessed with stellar environmental credentials.

Because cork consists of cells filled with air, the flooring never feels cold, and it always gives your feet a little spring. When you walk on a cork floor, you're literally walking on shock absorbers -- a boon to tired legs and feet. The air also deadens sound and reduces vibration, which makes cork floors remarkably quiet, a particular benefit if another floor is underneath.

Cork flooring is made from scraps left after wine corks are punched from the thick, spongy bark of the cork oak tree, Quercus suber , which grows primarily in Spain and Portugal but also is found in other arid areas, including Morocco and Algeria. Using only hand tools, harvesters literally peel off the bark in sheets. As long as they work carefully and wait at least nine years for the next harvest, the process doesn't hurt the trees, some of which are more than 200 years old.

Once they punch out the wine corks, manufacturers grind up the rest of the bark. They mix the granules with a little adhesive and press them into sheets. These are cut into flooring tiles or bonded to other materials to make plank flooring.

Cork flooring undergoes greater pressure and is therefore considerably denser than the cork found in bulletin boards. But basic cork flooring does look similar, which is not always what consumers want. To enliven the look, manufacturers sometimes heat the granules, which causes natural sugars in the bark to caramelize, just as sugar does in a pan on a stove. By mixing the natural, tan-colored granules with darker granules in various proportions, companies produce different styles of cork flooring without the use of dye.

In addition, at least one manufacturer (Globus Cork, ) now makes vibrantly colored cork flooring in shades that range from lemon yellow to scarlet to royal blue.

To create even more variety and respond to consumers' apparently insatiable desire for products that look unusual, some manufacturers produce cork flooring that has a thin veneer layer bonded to the top of the cork. Veneers may feature lacey cork burls or other delightful details, but there is one inescapable truth about these styles: The veneer is only paper-thin. In a bedroom, it might work fine. In a kitchen, the veneer is likely to wear off where you walk most often. Go instead with a style in which the cork pattern extends all the way through.

There are two basic types of cork flooring: traditional tiles and laminate. Traditional tiles are typically about 3/16 -inch thick and perhaps 12 inches square. Installers glue them directly to a plywood subfloor or to concrete, just as they would attach linoleum or other sheet flooring. The tiles can go in any room of a house. The cork itself doesn't absorb water because the air cells in the bark are closed, so you can use traditional tiles even in a bathroom or other area where water might get on the surface. Water can still seep down between the joints, however, so you should never flood the floor with water.

The laminate style consists of multiple layers of material. A top layer of compressed cork is typically bonded to a middle layer of medium-density fiberboard (a type of dense particleboard), which in turn is bonded to a bottom layer of uncompressed cork. This laminate type is often called a "floating floor" because the pieces have tongue-and-groove edges that either click together or can be glued together to create a floor that "floats" on top of whatever is underneath.

Laminate-style cork is a good choice if your existing flooring is in rough shape and you don't want to tear it out, perhaps because it contains asbestos fibers. Installing laminate-style cork is quick and easy. But you must leave a gap at all edges so the floor can expand and contract as humidity changes. To cover this gap, you'll probably need to add a strip of molding at the bottom of the baseboard. Also, the new flooring will be higher than the old, so you may wind up with shorter toe kicks at cabinet bases and awkward elevation changes between rooms, if you are using the cork in only part of your house. Laminate-style cork is suitable for most rooms, but keep it out of bathrooms, basements or other locations where water may collect. If moisture gets to the middle layer, the wood fibers will swell and the flooring will warp permanently.

Manufacturers usually add a finish to laminate-style flooring at the factory. Traditional tiles may be pre-finished or sold bare, to be topped with a finish after installation. Your options include polyurethane or other plastic-type floor finishes, as well as wax or oil-and-wax finishes. The plastic finishes are tougher but more difficult to refinish when they do eventually wear through. The wax and oil-and-wax finishes need more frequent attention, but with regular care they last indefinitely.

Cork doesn't dent or scratch as much as other types of wood flooring because the cork cells compress when a heavy load is on them, then spring back into shape once that load is lifted. But the finish layer can still be scratched or worn away. So it's important to vacuum up grit promptly. To remove sticky spills, wipe with a damp cloth.

Over time, the ultraviolet rays in sunlight cause cork to fade. If you cover part of the floor with a carpet and then remove the carpet, its imprint will show. Keeping windows covered reduces this effect.

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