Cork Flooring

Historical Use and growth of industry:

Cork flooring has been around for hundreds of years, with reports of its use dating back to the mid 1700’s in Egypt.  Though there is little as far a written record of cork flooring from that point to the late 1800’s, we know there were a number of prominent installations in the US, some of which still exist today.  Then in the 40’s and 50’s, cork flooring began to be used more, mainly in residential kitchens and dens.  When the 60’s came around, that resurgence declined, and didn’t really pick up again until the 90’s when its’ claims of environmental sustainability became more important to the buying public and growing “green building” movement.  This resurgence appears to be here to stay, not only due to improvements in the product and how it performs, but the Portuguese government has realized how important “cork” is to their economic survival, and has begun global partnership marketing to ensure cork as a material is seen as a positive in consumers’ eyes.

As the flooring segment has developed, so have the products being made.  Way back when at the beginning, cork from the cork oak tree was shredded into various sizes and shapes, and then mixed with a binder before being compressed and cured into a block shape.  Once in a block form, it could then be cut into the desired thickness of the required tile.  At the beginning the tiles were all made just of a conglomerated mass of the granules – definitely lacking any design element or style.  This is likely why cork flooring had several “so-so” introductions into the market – it was bland and homogenous.  As the product became more popular and manufacturers learned new ways of processing the material, the use of veneers in the product has become very popular as it enables a new set of aesthetics that you can not affordably achieve in a conglomerate-only manufacturing effort.  For making the veneered products, they essentially create a customized block (highly arranged and patterned, occasionally also adding color in the matrix) and then cut the material very thin, before mounting it onto the conglomerated backing.  This opened up the number of aesthetics available in cork, widely.  Any pattern that can be created with chunks, pieces and conglomerated particulates of cork, can be duplicated in mass scale using the veneer production technique.

Different options/types:

Cork flooring is available in a number of different options: tiles, planks, and mosaic.  Each option has its’ own set of benefits and attributes that help narrow down the focus when it is decision time.

The tiles are made of 100% cork, and are installed via a glue-down installation method.  Though installation methods can vary, it makes the most sense to use contact cement for the application.  Since the cork tiles are made flat, but are soft and flexible, it is important that when installed the bond is created instantly, or there is a high degree of likelihood that the edges will lift up (ie: curl) before the glue bond will hold it.  In addition to the need to set quickly, it is also important that the tiles are “rolled” with weight to ensure there are no air pockets in between the subfloor and the tile.  Being flexible and thin, the tiles also tend to mimic the shape and pattern of the subfloor below, making it essential that the subfloor is very flat and smooth – if it is not, any of these inconsistencies will telescope through the material and appear larger on the surface.

Cork planks essentially have a cork tile on the top of either an MDF (medium density fiberboard) or HDF (high density fiberboard) core, and then is balanced and protected with a cork under-layer at the base.  This 3-ply construction enables the material to “float” on the subfloor, meaning the planks are fastened to one another, but are not physically attached to the subfloor.  Not only does this solve the issue if the subfloor is not perfectly flat (as important with the tiles), it also tends to ensure that the floor moves as a unit, as opposed to have having the individual pieces move independent of one another, as with the tiles.  The MDF/HDF core material though, unlike the tiles, tends to be very sensitive to moisture.  Once deformed, it does not come back to its’ original shape, so it is important to make sure the planks are effectively isolated from prolonged water contact.  Cork planks tend to be a relatively easy product to install, ideal for handy DIY’ers, or for quick professional installation.

The cork mosaic is a relatively new entrance into the cork flooring market, and it is a flexible mosaic sheet topped with either cork discs or irregular cork shaped scraps.  The disc version is made by cutting post-industrial wine corks into ¼” pieces.  The irregular scrap mosaic is made by thicker, though consistently thick chunks, and laminating that to the backing.  Within each of these two main patterns, there are also different styles, based on whether the raw material is conglomerated (for the discs, like those typically used in Champagne bottles) or from un-adultered raw cork (would show air pockets, etc.).  The mosaic sheets install in a similar fashion to a stone and ceramic mosaic, but what is so unique is that the mosaic sheets are suitable in heavily water prone areas (like showers, pool surrounds, etc.).

Comparison to traditional products:

The comparison of cork flooring to other traditional products depends obviously on the type of cork used and what it is being compared to.  Some general points of comparison are hardness, thermal and acoustic insulative values, and installation.

Cork is a relatively soft material in the traditional sense when compared to other “woods”, but it is not a 1-to-1 comparison since cork has greater impact memory than any other wood.  Further explained, cork will temporarily dent more easily with a high point load, but it will rebound, unlike other woods that permanently deform.  This is due to the cellular structure of the cork material, and the fact that cork is mainly microscopic pockets of air with a resilient exterior between the pockets (like bee honey combs).  Depending on the coating used on the cork (ie: normal urethane, oil, nano-ceramic urethane, etc.), these softness attributes can either be embellished or diminished.

Cork, again due to the fact of the cellular pockets of air, has unmatched acoustic and thermal insulation values when compared to any other wood.  This helps deaden sound between spaces (both impact sound, IIC, and sound between adjacent rooms, STC).  From a thermal standpoint, the use of cork also keeps a cold climate house warmer in the winter, than would another product.  The thermal insulation and reflection properties of cork flooring are one of its main advantages, and definitely understood knowing that prior to the development of Styrofoam, cork was used inside refrigerators and freezers.

The installation of the cork flooring is quite comparable to installing other woods and products.  Cork tiles glue down in a similar fashion to vinyl (VCT – Vinyl Composite Tile), as that is probably the closest kin.  The planks install more like a laminate than a traditional hardwood since this is engineered on a fiberboard backing.  The cork mosaic installs in a similar fashion to a stone mosaic, though it can also be installed with wood-based glue if installing in areas without water.

Insider Knowledge and potential for market confusion:

There is some important background information that is helpful to understand: cork material as it relates to its’ maturity and source of origin, chemical components of the plank core material, and the differences a certain “finish” can have on the resulting cork flooring product.

The majority of the cork flooring used globally comes from the Mediterranean region, where most of the cork comes from.  It has been part of their culture and industry for hundreds of years, and it is fair to say they lead the intellectual use relative to processing and manufacturing.  They understand it, like it is their kin – it is essentially the life-blood of their economy.  Interestingly though, China is emerging not only as a global power, but as a cork producer and manufacturer.  Arguably, China is quick to see trends and then act upon them, and with cork it is no different other than the reality that they do not have the cork forests that Portugal has, both in volume/quantity and age.  As referenced earlier, cork trees take between 25-35 years to reach a level of maturity before the cork bark is ideal for use in value-added production.  Being essentially the new kid on the block, China has not known or physically gone through the maturation growth period that would enable mature cork material for use in their production.  Eventually, decades later, they will likely have abundant mature stock, but not now.  So, current cork products coming from China, or at least those made with Chinese cork (ie: most, if not all; since it would be too expensive to export Portuguese raw material cork to China to further produce a competitively priced export), have different properties, as well as a different look.  The immature cork tends to be more brittle, slightly darker, and lacks the acoustic and thermal values inherent in mature material.  Chinese cork tends to be less expensive than Portuguese cork due mainly to the fact that they do not have to wait and/or pay for the more expensive, properly harvested cork material.

Somewhat related to this, is the discussion of toxicity of the cork material on the planks, and by toxicity the main concern is formaldehyde emissions.  The planks are made with either a MDF or HDF core, and this essentially saw dust mixed with glue.  The glue can either be low-VOC and inert, or higher VOC and potentially lead to increased levels of airborne toxins emitted from the material.  All of this core material coming from Portugal is from one of 2 factories, and it is all considered low-VOC and E1 compliant.  The origin of the core material used in the Chinese cork is unknown at best.

Not only does the cork materials’ source and age affect the flooring made, the resulting durability of cork is also affected by the finish used on the product.  Cork, being relatively soft, is extremely resilient, but the clarifier is that it is resilient as long as there are not high point loads which are dragged, or otherwise pulled across a floor’s surface.  This can tear the finish, depending on the finish used and how it is applied.  Traditional urethanes (most cork uses water-based urethanes due to its’ added flexibility) tend to be a surficial plasticized topcoat, that can tear, and depending on the level of sheen, can be quite noticeable.  In recent history, cork flooring has had some bad press due to the scratching of the finish, and this, by and large, would be for the urethane top-coating materials.  Oil and waxes tend to be more matte in sheen, and scratches and marring tends to be less noticeable, though the cork can still tear with a pulled high point load.  The relatively new nano-ceramic coating basically adds microscopic ceramic particles to the urethane, making it almost impossible to wear through.  This now makes mid-to-high traffic commercial applications a playground for cork flooring with the ceramic nano-finish.  Though the degree of softness takes a slight ding, the acoustics and thermal values remain, and it makes for a much more durable product in extreme wear conditions.

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