Getting Corked: a Guide to Installing Cork Floor Coverings
Cork is considered one of the most environmentally friendly flooring materials available today because it is made from the bark of the cork oak tree, which re-grows every nine years. The tree actually recycles its own bark, which is stripped without damaging the tree or affecting the birds or other animals that live in the cork forests, most of which are in the Mediterranean region. Portugal is the largest producer of cork, and Spain and several other countries in the area also have cork forests.
Because cork is 50 percent air, cork flooring is a natural insulator, and has softness under foot that is unique to this material. There are three cork flooring products in common use today - cork with a vinyl backing and a vinyl wearlayer, natural cork tile which is cork through and through, and cork floating floor, which has a cork top, a cork backing and a fiberboard core. All three products can be made homogeneous (color throughout the wear surface) or with veneer layers that provide unique visuals. Cork can also be stained, either at the factory or on site, much like wood flooring.
All cork flooring products need to be handled carefully and installed correctly, and there are several keys to success to a successful installation. Cork is a sensitive natural material that needs to be done just right, so don't be tempted to ignore any of these guidelines.
• Manufacturer's instructions: Unlike some other resilient categories where most materials are installed pretty much the same way, cork manufacturers often have different guidelines. Having the manufacturer's installation instructions is the first place to start. Make sure you do the job "by the book," and that you have the right book.
• Building conditions: Like wood, cork is subject to changes in dimension due to temperature, humidity, and moisture. If the building is not enclosed with the heat or air conditioning running, don't do the job. Also, a cork floor should only be installed after all the other trades are finished to prevent any possibility of damage to the floor. A cork floor needs to be the last part of any construction project.
• 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*.
• Acclimation: The material needs to be on the job three days or longer before installation to acclimate to the job site temperature and humidity conditions.
• Shading variations: Like a wood floor, no two cork tiles or cork planks are alike, so make sure the customer knows this and "shuffle" the product so the variations are randomly spaced throughout the floor.
• Training: If you are uncertain about working with cork, request that the manufacturer send someone to spend a little time before you start the job. Even just a one hour training session may go a long way to making you more comfortable with the process.
Don't even think about starting a cork job without all of these guidelines in place. To continue, there are unique characteristics to cork tile and cork floating floors.
For cork tile, whether vinyl backed or natural cork, the adhesive specification and application is critical. Don't switch adhesives to save a few pennies. Go with the manufacturer's specification for adhesive. Even if you find an alternative that is not on the manufacturer's list and the adhesive manufacturer recommends their product for cork, don't use it unless the adhesive manufacturer will warrantee the floor in case of a failure. That means the cost of removing the failed floor, preparing the substrate, the cost of the new tile and adhesive, and the labor for reinstalling the floor. Cork is a big ticket item if it has to be replaced! Another key is how the manufacturer recommends applying the adhesive. Get brand new trowels or paint rollers, as specified.
If the subfloor is wood, it needs to be flat and smooth, which almost always means installing a high quality underlayment. Installing directly over an existing resilient floor covering is not a good idea.
For natural cork tile, there are two different methods for installation. The traditional method uses a contact type adhesive applied to the back of the tile and also to the floor using a medium nap paint roller. This method really holds the tile in place, but you need to be sure the back of the tile is completely covered with adhesive. This can be done the day before, because as soon as the adhesive dries, you can stack the tile up so it is ready for the next day's installation. Just be sure to stack them front to back, not back to back, or you'll never get the tiles apart. When installing, make sure that you place the tile exactly where you want it to be because it does not move once the two surfaces make contact. Many products in today's market have the adhesive pre-applied to the backing so all the installer has to do is apply adhesive to the floor, with either with a roller or with a trowel, depending on the type of adhesive being used. Check on this detail before bidding the job. As far as adhesive application to the floor, proper coverage is important. If the spec calls for application with a paint roller, you can do it standing up, which is good for your knees. If the substrate is on the porous side, it may be necessary to apply a second coat of adhesive after the first one is dry to be sure you have good coverage. For trowel applied adhesive, pay careful attention to the trowel notch size and make sure you replace trowels often on larger jobs as the teeth wear down. Also, check your open time, as you should for any floor covering that is glued down. If you spread more adhesive than you can cover in the required open time, you'll wind up having to scrape the adhesive off the floor because the flooring won't adhere. Plan enough time for the job so that you can take your time and do the job right.
After setting cork tile in to the adhesive, it needs to be pressed in place using either a rubber mallet or a roller, or both. Again, check with the manufacturer. Don't skip this step, as cork can tend to curl a little. Making sure the tile is properly set into the adhesive by rolling and/or malleting will prevent this from being a problem.
Cork floating floors are installed in a very similar way to floating laminate or hardwood floors. The cork industry is in the process of converting to the glueless "click" type installation system, but some products still use the traditional glued floating tongue and groove installation method. Even with the glueless system, it may be advisable to use an adhesive in commercial installations or other heavy traffic areas. The adhesive provides an extra level of protection and durability.
Like all floating floors, make sure the substrate is level and smooth. Any dips or high spots in the floor need to be corrected. It can be installed over an existing resilient floor that is level and good shape, or can go over a hardwood floor, plywood, or a variety of other flooring materials.
Because cork floating floor has a cork backing, it is not necessary to install a foam underlayment over a wood subfloor as you would with other floating floors. You do have the option of using a cork or foam underlayment for extra softness or sound deadening, but it is not required. However, when installing over concrete, a vapor barrier sheet must be applied to protect the flooring from any possible moisture vapor emission from the slab. The vapor barrier can be plastic sheeting or other vapor barrier system that is approved by the cork manufacturer. Make sure the barrier seams are properly sealed and the edges are treated correctly. When installing the cork floating floor, follow the same guidelines as for any other floating floor. Use a saw to cut the boards, stagger the ends of the boards appropriately and allow proper expansion against walls, other fixed objects, and doorways. There are no matching cork moldings, so prior to doing the job make sure wood moldings are selected that are acceptable to the customer. For example, for natural colored cork, a medium "gunstock" oak colored molding looks great.
For all installations using adhesive - whether tile or floating, tell the owner to keep traffic and furniture off the floor for at least a day or two. This will allow the adhesive to dry and be mostly cured.
There are two types of finishes on cork floors today - unfinished or prefinished (waxed, oil, or urethane finish). The unfinished surface needs to be screened, stained or sealed, and finished before the floor can be used. If your company is not responsible for this work, make sure the floor is completely covered when you are done to protect the raw cork surface. Use brown kraft paper, not plastic, so that the floor can still "breathe" and the adhesive can dry.
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 fifteen years or so, cork is making a comeback because it is an environmentally friendly, soft, warm and beautiful flooring material. As Cork Flooring continues to grow in popularity, installers who understand this product will have plenty of work.