Cork: The Sustainable Alternative To Hardwood Floors
Cork is a renewable resource and has become a "green" alternative to hardwood floors. Cork is more than just a material for wine bottle stoppers and bulletin boards. When most people think about cork, they don't think about flooring. Even though cork flooring is a fairly new phenomenon, its popularity is growing fast. It has been receiving attention since the early twentieth century.
So what makes it renewable resource? Simply, the way it is harvested. Cork is produced from the cork oak tree. It is an evergreen oak tree that is native to southwest Europe and northwest Africa. The world's largest producer of cork is Portugal. The bark is peeled away from the trunk of the tree and the branches. The harvest takes place in the spring or when the tree is growing strongly and the bark comes away easily. This can be done every 9-12 years when the bark regenerates itself. The tree does not need to be cut down to make cork floors. In fact, the average cork oak tree lives for 150 to 200 years. The bark of a cork oak tree can be harvested around 15 times safely. The tree has to be mature, at least 20 years old. The material only comes from the bark. None of the tree is actually cut down. In other words, neither the trees nor the habitat are affected or harmed when cork is harvested. The tree is replaced with a much younger cork oak. When you remove the bark, it doesn't impact the tree negatively. A lot of other trees, like birch, cannot survive without their bark. The cork bark is removed carefully with a specially designed hatchet by hand in 1x3 sections. It has a 3-6 month aging process. After this process is complete, the cork is shipped off for commercial use.
Cork is one of the most renewable wood products for a floor covering. These trees are protected. Only about two-thirds of the bark is removed from the tree. The tree has enough bark left to make a natural defense and to ensure a long life. The cork oak tree has a protective layer of inner bark. When the bark is harvested, this inner bark still remains on the tree. This inner bark makes it possible for the cork oak tree to survive after it has been debarked. When the bark is stripped, the inner bark cannot be damaged. It has to stay completely in tact if the tree is to remain healthy.
A lot of people compare cork to bamboo for its environmental impact. As you now know, cork is harvested in a very different way than bamboo. Bamboo is cut down in order to be harvested and cork is not. A lot of people want to have a "green" floor. They usually have to decide between cork and bamboo. Cork is obviously the more sustainable choice. (Check out my article, "The Truth About Bamboo Flooring" to get the entire scoop.)
The quality of cork can vary from one forest to the next as well as from one tree to the next. Also the amount of sunlight that it gets can impact the quality. So, for industry that purchases cork, there are a variety of things to consider when it comes to the quality of cork. The quality of the tree will largely impact the quality of the floor. A healthier, stronger tree will make a more durable floor covering.
Cork is processed in a rather simple way. The bark is seasoned to create a uniform moisture level. Traditionally, the bark was seasoned on bare earth. If cork is drying in the forest for several months, it will be susceptible to microbial contamination. Often today you will see the bark stacked on concrete in factories. This is done to inhibit microbial growth. It is boiled to remove the woody outer layer. This makes the bark more elastic so that it can be flattened out. Then the bark is sorted into different piles according to its thickness. Each of these piles of bark is sorted further based on other characteristics.
The bark of a cork oak tree is unique. Cork bark is made up of a tiny sealed honeycomb cellular structure. Each cell has a 14-sided shape. This means that there is virtually no space between each cell. These cells provide cushioning and insulation. For one cubic inch of cork, there are over 100 million enclosed air cells. Each enclosed air cell is 1/1000" in diameter. Because of all the air in cork, it makes a very lightweight material. One cubic inch of cork can withstand approximately 14,000 pounds of pressure per square inch without breaking. It will also hold most of its original form when it has been compressed. If compressed up to 40%, cork will turn to its original shape quickly. The reason why it compresses and goes back to its original state so easily is because the air pockets are able to collapse and bounce back again. To put it more simply, if you take a balloon that is blown up and release the air in it and blow it up again this is more or less what is happening. When the balloon has no air in it, it is like the compressed cork under pressure. The air in cork gets displaced allowing the material to compress when under pressure. When the pressure is released, the air in the cork will go back to its original position. This is what makes cork a unique floor material.
Now that you know why cork is a renewable resource, let's see why people pick it as a floor covering. Cork makes a relatively soundproof floor. It works well in apartments where you have neighbors above and below you. Also, you will feel vibrations through this floor a lot less than with other flooring types. Cork flooring absorbs sound and vibration. If you drop a heavy object, usually it won't impact the floor that much. If you drop a glass or any breakable object on cork, chances are that it probably won't break. The impact of the fallen object gets absorbed in cork flooring. A cork floor is firm but not bouncy. The reason for the serious noise reduction from cork is because it is incredibly dense and has a unique cellular structure that is impregnated with lots of air.
Cork also insulates well. It provides natural thermal insulation. Some people even say that they have cut their energy bills by having cork flooring throughout their homes. The "dead" air space in cork makes it an efficient non-conductor of heat. This means it reduces air movement. When you walk on a carpet, it is warm because it is not absorbing the heat from your feet. Differently, a tile floor is taking the heat away from your feet. This makes the tile floor feel cold. Cork doesn't absorb heat. This is why it feels warm to walk on barefoot.
One of the most prominent reasons that people choose cork is because it is soft ad cushioning. Cork is appealing to the elderly because it has shock-absorbing qualities. For people who suffer from back and joint pain, this is ideal. For kids who take the occasional tumble, cork flooring provides a softer surface to break a fall. It makes for a comfortable under footing. It provides relief for your feet, back and legs. The reason why it is shock-absorbing is because lots of air is trapped in cork. It is the same reason that it is relatively soundproof and absorbs vibrations. About 50% of cork is air. This is why it is a cushioning floor. Despite its soft, rubbery feeling, it is actually a durable floor that does not scuff very easily.
Cork is known as quite a resilient floor covering. Cork has a lot of give to it. It is recommended for areas where there is going to be extensive walking or standing. Because of its natural resiliency, cork is commonly found in high traffic areas like government buildings, churches, libraries and banks. It is a flexible, relatively durable floor covering.
An advantage to cork is that it is very comfortable for people who suffer from allergies. It does not absorb dust. Some manufacturers even coat cork floors with anti-microbial or paraffin oil treatments to inhibit the growth of mold, mildew and bacteria. This improves the indoor air quality. Green Building Supply Environmentally Friendly Home Center uses JointShield, which is a paraffin oil product. This is designed to impregnate the joints, making the floor watertight. This creates a strong moisture barrier. On the other hand, if cork floors do not have a protective coating, they will be susceptible to damage from mold and mildew. This will happen typically in kitchens, bathrooms and basements where moisture levels are higher. I highly recommend a polyethylene water barrier.
Suberin is a natural, waxy substance that is found in cork. Cork naturally resists insects and termites because it contains suberin. This waxy substance also protects cork from rotting if it is slightly wet for a while. (Obviously, the amount of water on a cork floor should be minimal. It will get damaged if there is a lot of water on it, just like any other floor covering.) Its cellular structure doesn't make it waterproof, but it helps repel water. With a proper binder, a cork floor can be fairly water resistant. Suberin is also fire resistant. It won't spread flame. It also will not release gas during combustion. For people with sensitivities, cork is popular because it is formaldehyde-free. It does not give off gas unlike a lot of other floor coverings.
Cork flooring is not a new phenomenon. However, new forms of cork flooring have come out in recent years. The newer varieties of flooring are tiles and planks with snap or click lock joints. Cork is even available in the parquet format. It has become popular because these new styles of cork flooring are easier to install and don't use any glue. It doesn't require a skilled floor contractor to install a cork floor. It is appealing for a DIYer. Most cork flooring comes factory finished with a topcoat of UV cured acrylic or a water-base.
Modern manufacturing practices compress cork so that there are a huge variety of rich textures, patterns and colors. The problem with the colored varieties is that scratches and wear marks show up more prominently than they do on natural cork. Also, a lot of people have had problems with dark colors turning much lighter pretty quickly. Some companies mix rubber with cork to get special texture. In my opinion, this is not a healthy choice. Rubber is an off-gassing material that will emit gas for a very long time. The diverse styles make cork flooring very appealing for consumers. Cork floor can be tailored to the consumer. There is going to be a style of cork flooring that suits your needs. Cork floors are very easy to maintain. They only require vacuuming and the occasional damp mopping.
Cork floors look nothing like hardwood floors. Environmentally conscious consumers favor cork. This is because they are not destroying forests. They don't have to worry if the tree that was used to make their floors will be replaced with a new tree. Cork is a popular choice because if it is coated properly it is fairly resistant to scuffs. If it has a poor finishing, most people will be pretty unhappy because it will scuff easily. Some kinds of cork are not as strong and long lasting. Some varieties of cork can be so soft and squishy that you can carve your name into the surface of the cork flooring. This is not very appealing to some people because they know they will develop many indents on their floors overtime.
If you decide to go with cork, it is available in unfinished or prefinished. There are three varieties for cork flooring. They come in planks, standard tiles and mosaic tiles. There are also a few options for finishes. A cork floor can be finished in acrylic, urethane or wax. These floors can be left in their natural color or they can be stained or even painted. Cork can also be solid or laminate.
Traditional panel cork floors are installed like tongue and groove. They are interlocking boards. However, there are new forms of cork floor that have been designed so they are easy for anyone to install. For example, Green Building Supply Environmentally Friendly Home Center has what they call UniClick, which is a patented European design. This is a style of floorboards that click together like a gigantic puzzle.
A cork floor can be a floating floor. This is a glueless construction. The floating floor panel is cork. There is a stabilizing core above the floating floor. The stabilizing core is either made from high density fiberboard (HDF) or medium density fiberboard (MDF). The edges of the panels are milled so that they interlock adjoining pieces. The cork core is the next layer. This layer varies depending on the manufacturer. Its purpose is to provide impact absorption and insulation. The cork bark veneer is the top layer of the floor. It is either be a veneer from the tree bark or cork that has been processed to get a certain pattern or texture. The wear surface can either have a factory finish or a finish that the consumer chooses.
Installing cork floors are not that different from installing hardwood floors. I strongly suggest that if you get a cork floor, use the manufacturer's guidelines for installing it. This will always protect you should something go wrong. (Not to say that it will, but you always rather be safe than sorry!) I have read through the instillation instructions for AmCork (American Cork Products Company). They state clearly that you must adhere your floor tiles using DriTac 6200. They give specific brands of polyurethane as well. These include the product Traffic by BonaKemi or the product X-Terra by DuraSeal. If you use either of these polyurethanes, you will be protected under their 25 year warranty. In other words, if you deviate from their product suggestions, you will immediately void your cork floor warranty! There area lots of varnishes on the market that are really poor quality. They are not strong enough to hold up, especially some of the residential grade ones. The weaker the varnish, the more likely your cork floor will gouge.
Cork floors can be installed on concrete. The underlayment should be 1/4". Like any other wood floor, the concrete must be level and smooth. If it is uneven, you will surely run into problems. The moisture level should not exceed 3 pounds in a 1,000 square foot area. If you are installing cork overtop plywood, the plywood should be 1/2 and inch thick. It is best not to install cork floors over a radiant heat system. Cork expands and contracts a lot. In the summer when it is hot, their will be noticeable gaps in your floor, should you decide to install a cork floor over a radiant heat system. When you lay cork, you want the pattern to look unique. The best thing to do is open up all of your cartons of cork and lay them side by side from different cartons. The more you mix the tiles, the more variety of colors and patterns you will yield. You also want to leave 1/4" expansion space because cork will expand just like other types of wood flooring. Also, if moisture levels are high, your cork floor should be installed rather tightly. If moisture levels are relatively low, you should lay your cork floor not too snugly. You want your cork floor to have room to expand when the moisture content level rises. If you do not do a moisture test and you find out the hard way that you have too much moisture, you will have to rip up your cork floor. If cork is laid on moist or damp concrete, overtime it will create a balloon effect. Cork will puff up or swell as much as it can.
The fancier varieties and the engineered kind of cork have a paper thin wear layer over a cork composite cushion layer. If this layer is very thin, it will more than likely get damaged easily. If you have a dog, it may not even scratch the floor, it may gouge the floor! These types of cork should never ever be used in high traffic areas. The unique characteristic about cork is that the patterns tend to be so busy that scratches blend in. So if you do have a gauge or ding in your floor, you can use some cork filler and polyurethane. Moving furniture, dropping a kitchen pot or wearing high heal shoes is enough to gauge your cork floor. More than likely the ding will blend in. Like hardwood floors, cork is quite durable if maintained properly. It also requires a certain kind of maintenance. However, sharp objects will permanently scratch a cork floor. Unlike hardwood floors, cork cannot be sanded down. If the scratches don't blend in, there is nothing you can really do about them.
If you go with cork tiles, they are so flexible that the edges may curl up over time, not the topcoat of finish but the cork itself. However, if you have problems with a single tile or an area of tiles, they can be broken up and ripped out on their own. Smooth out the underlayment. Install a new tile. You don't need to take up the entire cork floor! It is an easy D.I.Y. job for a weekend.
Cork can be almost as durable as hardwood floors if it is properly maintained. If you go with a strong finish, chances are that it won't scratch or gauge too quickly. A cork floor can easily be refinished but it cannot be sanded down to get rid of scratches. Once you have scratches, they are there to stay! A cork floor should last upwards of 30 years if treated properly. In contrast, a hardwood floor will last you between 100 and 300 years if properly maintained. There are both positives and negatives to cork floors. The most important thing to keep in mind if you are deciding on cork is your lifestyle. If you are the type of person that redecorates a room frequently and moves furniture often, cork is not for you. If you plop your furniture down and don't move it around often and you like walking around barefoot, this might be a very appealing floor.