Cork flooring is one of the most interesting floor covering products in use today, but is also one of the most misunderstood. This is something I learned this year when I started presenting a seminar called "The Fascinating World of Cork." The presentations had me fielding a variety of questions about this century old flooring material. It led me to believe that there are still many in the business who could use an overview on cork flooring.
Cork's growing popularity stems from a number of factors but one of its chief attributes is that it is "environmentally friendly." No trees need fall to harvest cork. It is derived from the bark of the cork oak tree. After it is stripped from the tree it re-grows approximately every nine years. Portugal has long been the largest producer of cork followed by its neighbor Spain and several other countries in the Mediterranean region that have vast forests of cork tree.
The most widely used cork product, of course, is the one that ends up in a wine bottle. The remaining cork material is ground into particles and compressed under heat and pressure into blocks known as agglomerated cork, which is sliced into various thicknesses depending on the product being manufactured. Gaskets, expansion joints, shoe soles, bulletin boards, floor coverings, and many other materials are made from agglomerated cork. What makes cork so desirable? It has a unique cellular structure that is at least 50 percent air. As a result cork is a good choice for flooring: It is a natural heat and sound insulator and has softness under foot that is unique to this material.
Although classified as resilient flooring, cork floors have many of the same characteristics as wood flooring with regard to handling, installation and finishing. With a little bit of research and careful attention to detail, flooring dealers and installers should have no problem creating a beautiful installation of this timeless and beautiful floor covering.
Currently there are three cork flooring products commonly used today: Cork with a vinyl backing and a vinyl wearlayer, cork floating floor, and the traditional natural cork tile, which is probably the most intimidating product of the three. So let's focus on that one and look at some common questions:
Where should cork flooring be used?Like wood, cork is not ideal for every location. Cork bounces back very well from indentation, but like any other resilient or wood floor, it can be damaged by water, heavy loads, direct sunlight and heavy objects being dragged across the floor. It needs to be used where it will not be abused and where it will be maintained correctly.
Can it be sanded?That depends. There are two types of cork flooring: homogeneous and veneer. Homogeneous has consistent color all the way through, so it can be sanded and refinished just like many wood floors. Veneer cork flooring has a thin layer that provides unique visuals, but it cannot be sanded. They are not the "forever floor" that homogeneous cork floors can be.
When is the best time to install it?Last. Like wood, cork is subject to changes in dimension due to temperature, humidity, and moisture. If the building is not yet enclosed with heat or AC running, don't do the job. It should only be installed after the other trades are finished to avoid the possibility of damage to the floor.
What are the proper substrate conditions?Substrates need to be dry, flat, smooth and clean. Prepare and test concrete according to the manufacturer's guidelines and ASTM F 710, Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring (available from ASTM International at www.astm.org) This means moisture testing of concrete slabs, and proper preparation to be sure you have a flat and smooth substrate.
Does cork require acclimation?Yes. Have the material delivered to the job site at least three days before installation to make certain it can acclimate to job site temperature and humidity. Having it in your warehouse and then bringing it to the job site does not count.
What if the shade varies among the tiles?Like wood, no two cork tiles are precisely alike. (Salespeople, do us installers a favor and make sure your customers know this.) Installers should "shuffle" the product so the variations are randomly spaced throughout the floor. If you have a seriously "off color" piece, don't install it.
How important are the manufacturer's instructions?Extremely. Unlike some other resilient products where most materials are installed pretty much the same way, cork manufacturers often have different guidelines. Do yourself a big favor and read the manufacturer's installation instructions cover to cover and use the manufacturer's recommended adhesive and new trowels or paint rollers (depending on whether you are using a trowel applied or a contact type adhesive.)
What about adhesive?The traditional method uses a contact type adhesive applied to the back of the tile and also to the floor using a paint roller. The adhesive on the tile can be pre-applied at the factory or on the job 24 hours in advance. The contact method really holds the tile in place with no curled edges and the floor can be walked on immediately.
What about trowel applied adhesive?If the manufacturer allows for a trowel applied adhesive, pay careful attention to the trowel notch size and open time. If the adhesive is left open for too long, the flooring won't adhere properly and there will be curled edges.
How to you handle unfinished cork?Like unfinished wood. It must be finished before the floor can be used and it can also be stained to create a unique color. For companies that do a lot of "sand and finish" work for wood floors, this is a great way to go with cork too. It results in a smooth, flat and tight floor.
And factory urethane finish?With factory urethane cork, it is often recommended to screen the new floor and apply one or two additional coats of a cork-specific urethane, especially on commercial installations. This adds an extra level of protection to the floor, and will help smooth and seal the edges, since "over wood" or ledging is not unusual on factory urethane cork. This finishing work must be done by an experienced "sand and finish" specialist, and not by a floor maintenance technician or installer.
What about wax or oil finish floors?Wax cork is the "old fashioned" way, but it needs a lot of work to maintain and there are not that many maintenance people out there any more who know how to use "real" paste wax. Oil finish cork is relatively new to the cork market and is being used residentially. In both of these cases, follow the manufacturer's maintenance guidelines.
These and other questions about cork are likely to come up with increased frequency. It is not that cork is new. As far back as the 1920s, millions of square feet of cork flooring were installed in North America, but cork use fell off as other synthetic materials grew in popularity. For the past 15 years or so, cork has been making a comeback. As cork flooring continues to grow in popularity, flooring dealers and contractors who understand this product can position themselves as cork specialists. They are the ones who will get the business when others are intimidated or unfamiliar with this environmentally friendly, soft, warm and beautiful flooring material.