Cork: Revered Renewable Resource

I have a confession. Sometimes I like to think of myself as smart. There are many smart people, right? I have a degree. I made it thru 12 years of the military, that’s gotta count for something. My home state is world famous for “Yankee Ingenuity”. Smart right? Well, Not… So… Fast! I’ve been learning ALOT this last year after opening Green Builders Source. So many things that a laymen’s understanding didn’t do justice. Let me share my latest discovery! CORK! Cork Sample

Seems, my layman’s understanding of cork was woefully inadequate! Sure, there are the cork boards, the underlayment of engineered flooring, and then my personal favorite, the wine cork! Yummy! But it wasn’t until 1999 that I had even HEARD of a cork floor. Tile? Yup! Wood? Of course! Marble? Have you seen the Duomo in Florence? But Cork? Apparently it was all the rage in Europe! And I just lived in Europe for 5 years? How could I miss it? How?

Well, being the ever curious, I started to pay attention every time information on cork was available. Jump to 2008 and Cork is now a top player for any green building project. The top green choices almost always start with: Cork, Bamboo, Linoleum, and locally manufactured tile. Many don’t know why Cork is on the “Short list” for Green. Bamboo is obvious as it’s a grass, it can be harvested and rapidly renew its stalks for a future harvest. Tile is sustainable, that’s green. Linoleum is very natural and long lasting. But Cork? The harvesting of Cork is not yet as well known nor is how and from where it is harvested.

Cork oak cross sectionCork comes from the Cork Oak. A medium sized tree that can be found in southern Europe and northern Africa. An interesting piece of information that is quite indicative of our vocabulary is all trees generate cork as a layer between the old growth bark and the living inner plant cells. It is a major component of the tree bark that protects the inner growth cells and sapwood from disease, insects, and damage. (note this… it protects the tree from bacteria, insects, and damage) It can be harvested from any tree, but only the Cork Oak is commercially viable due to its thickness and ease of harvesting.

The harvesting is equally interesting and truly a sustainable commodity, if not entirely practical. A Cork Oak does live an amazingly long time, upwards of 200 years. However, the first harvest cannot be taken until the tree is 20 years old. This harvest is of poor grade and it is not till the cork has been harvested an additional 3 times, or when the tree is 50 that high grade cork is available. This thought quickly squelched my desire to create a Cork Oak orchard in Texas given my level of attention and interest would surely expire before the first harvest. I did entertain the “second generation” idea, but my children would probably be so bored of hearing of the future harvest, they surely would be interested in more rapidly rewarding endeavors. Maybe Bamboo is more our “speed”? That said, the following harvests can be made at 10 year intervals. This allows 15 or more harvests from one tree! Truly a quest for a forward thinking entrepreneur. Very forward thinking!

Here’s a summary from the Canada/Portugal Chamber website:

Given that a cork oak produces cork tissue until it is 150 or even 200 years old, during which time it Whistler - Worlds Oldest Cork Treemay be stripped 15 to 18 times, and that the average ages of trees presently in production is 85 years and that the area under plantation is growing by an average of 4% a year, cork production can look forward to a rosy future in Portugal. There are at present more than 600 industrial facilities operating in Portugal, employing a labor force of about 15,000. Cork products were exported in 1990 to the tune of 80,433,356,000 escudos (corresponding to 105,516 tons). In the same period natural cork stoppers accounted for 55% of total cork product exports. At 44,614,694,000 escudos, this trade is worth more than the export of Port Wine.

This only further clarifies that the commercial leaders in cork production are in Europe and Africa with Portugal producing 50% of the world’s supply. Don’t let the scarcity of the harvest locations fool you, however. Cork has a plethora of qualities that make it very desirable. It’s elastic in nature and near-water impermeable. It has low thermal conductivity, low density, fire resistance, and good energy absorption, antimicrobial, and resistant to insects, mold and mildew. (remember how it protected the tree as part of the bark?) All these factors make cork an excellent product for wine stoppers, sports equipment, sound management in musical instruments, and more. However, these qualities sound amazingly grand for use in construction.

Microscopic view of cork cellsCork cells are comprised mostly of air. This trait makes each cork cell act as a balloon or a gasket. Additionally, the cell walls contain a waxy substance called “suberin” which enhances the impermeable wall to liquids and air. The product qualities that are found from the features of cork are: reduced sound from dropped items or walking, cork has a natural feel, it insulates against temperature changes (It has an “R-factor” of 2.6), it is low maintenance, extremely durable, and above all, it looks great. I found during my research for this article that there are cork floor installs that are still in use today over one hundred years old! One is a church in Chicago that had cork flooring in 1890 and is still in use today! And I just learned that The Library of Congress has cork flooring installed. Did I mention the sound absorption! Libraries and museums love cork. So do child care facilities. Not that I quote “Bob Vila” much, but his website had this to say about cork: “Finished cork flooring can have the look of textured hardwood… the soft give of carpet, and the easy maintenance of vinyl….cork feels softer than hardwood and warm underfoot, making it an obvious alternative to carpet.

Because of its cellular composition, it is extremely durable and resilient. This makes it much less affected by impact or friction than hard surface floors such as wood, laminate or tile. One feature that I always get questioned on is its resilience. I too worried that such a “soft” product would fall victim to high heeled shoes and the like. Apparently that “elasticity” that I mentioned has a “bounce back” factor of 40%! So, no worries about your high heeled shoes! Once the pressure is off, the cellular structure returns to shape very quickly.

Ok, so now we know it’s water resistant, insect and bacteria resistant, resilient, durable, quiet, and insulating, what do you have to do to get some? First, there are suppliers all over including Green Builders Source. Check all your options, inquiring about thickness, colors, patterns, pre-sealed, and quality. Second, there are two options for installation. Your cork floor can be installed as glue down tiles or as a floating floor. The glue down tiles uses fewer materials, but requires a near perfect floor for installation. The floating floor with interlocking tongue-and-groove edges is easier to install, and repair, and ready to walk on, thus making it a popular flooring choice.

For the floating floor planks and tiles, the cork floor looks like any engineered hardwood. Locking or There is a wear surface made of a factory applied, UV rated varnish or sealer, a veneer of cork oak bark, a cork core, a moisture resistant hard rigid core, and a cork underlayment. This layered solution provides the best of both worlds. The price is on par with other engineered woods or ceramic tile, so any alternative should put cork within the same budget range.

Once you have decided on cork, and you think you have a source, before you install it, you better have a maintenance plan. Every floor requires maintenance right? Well, yes, that is true, but cork is a low maintenance floor. The good news just keeps getting better with this flooring, doesn’t it? The catch? There isn’t any. Pick up loose dirt with vacuum, broom or “swiffer®”. The most important step is to Damp mop. Do NOT Wet mop! Do NOT let water stand on the floor. Then spot treat any tough to clean areas. Water is cleaning solvent enough. If you have to add something, nothing more abrasive then a drop or two of dish soap. Given all the water-resistance of cork, the seams of the flooring would swell under standing water.

Photo from Pretty amazing, hun? I know that in the time it’s taken me to finish this article, I’ve walked the house twice to see which room would look best in that new Green Builders Source Cork Floor! It’s a toss-up between the children’s play room or the kitchen. I’ll keep you posted.

Angelique Grado
Green Builders Source

References for this page came from: Wikipedia, Nova Cork, Natural Cork, Bob Vila, Canada/Portugal Chamber,, and several .edu sites.

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