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Natural Building Colloquium - East 2006

source: Mark Piepkorn

Natural Floors

There are a wide variety of options for natural flooring available to today's builder. Of course, some of those have been available for hundreds, or even thousands, of years; others are more modern, using natural materials but manufactured by industrial processes. There are many requirements upon a floor — it has to look good, feel comfortable, last a long time, be easy to maintain, not cost too much, and in the case of in-floor radiant heating, support the heat distribution infrastructure for the house. Already a high level of functionality, there are indeed options available that can also be sourced locally, involve minimal processing, and do not release toxic chemicals into the house (formaldehyde-based binders and other chemicals commonly found in carpeting and other synthetic flooring and floor covering systems are some of the largest contributors to poor indoor air quality in modern homes).

Perhaps the most 'natural' of the natural flooring options, earthen floors are also the oldest — since the advent of shelter, people have been living on the dirt below their feet. Sure, that may be simple to do in a desert hut, but in a Maine winter? There are a variety of strategies to bring the earth back underfoot in our modern homes, depending on the foundation style and other variables in design. Modern earthen floors are made of the same materials as plasters and earthen walls — a mix of refined clay soil and sand, with colorants and other optional additives as desired. They are then oil-finished to create a durable, water-resistant, beautiful floor that is softer than concrete (therefore gentler on both one's back and one's dropped glass or fallen child), yet as sturdy as a softwood floor. Earth's greatest vulnerability is not water, as one might expect — the thorough saturation of oil takes care of that — but point loads, such as table and chair legs, stiletto high heels, and dog nails; these are generally addressed by furniture pads or coasters, lifestyle adaptation (like taking one's shoes off before entering the room), and appropriate location (such as using a different material in the dog room). As in wood flooring (particularly softwood), wear patterns may become apparent after a period of time; this can either be addressed by rebuffing with another coat of oil, or avoided by use of runners or floor rugs in high-traffic areas. Spot repairs are quite simple in the event of damage, and maintenance is also quite easy: broom, vacuum, and/or damp mop. Earthen floors have the advantage of being incredibly inexpensive and ecologically-benign — all the same principles apply to material sourcing as for cob, and can often be found for free on-site, or for very cheap from a nearby source. Coloring and tinting can be achieved as for plaster, by either using colored clays, adding in pigments to color the floor, or painting a clay paint onto the floor before finishing.

As mentioned above, there are different ways to introduce earthen floors depending on the nature of the structure. Earth floors require a very stable and level subfloor to avoid cracking and ensure an even, professional application. This can be achieved in a number of ways. If there is a concrete slab in place, this may well serve as the subfloor, as long as it is sound and true. A full concrete slab may be avoided entirely, however, if one is building directly on grade. For example, a frost wall foundation may be built around the perimeter of the structure, with additional foundation supports on the interior to support interior bearing walls or posts. Then, an earthen subfloor can be installed by compacting layers of a clay-sand-gravel soil mix, until level and stable (generally about 6"). If going over a basement or second floor, provisions will need to be made — particularly structurally — to support an adequate subfloor, but this can readily be designed into the program of the house. The finish floor itself is generally one or two half-inch layers of the fine clay-sand mix which is then applied onto the subfloor. Insulation must be accounted for (in the case of our example, a layer of 2" foam may be placed below the subfloor), as well as moisture issues — the floor should not be in direct contact with ground moisture, either in liquid or vapor form, whether over an earthen, concrete, or other subfloor. Given its massive nature, earthen floors are very well-suited to radiant heating, either by in-floor hydronic tubing or passive solar gain. If appropriately designed, earthen floors can be beautiful and functional additions to the home that are simple and inexpensive to install.
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Wood is one of the most common flooring options, and has many of the same benefits of earthen floors in regards to natural beauty, strength, durability, and ease of maintenance, as well as being significantly lighter. In our climate, we are also blessed with a palette of different colors, textures, and densities of wood from which to choose. From high-end hardwood native cherry flooring finished to a gloss, to oil-rubbed softwood spruce or pine farmhouse-style flooring, wood can be integrated into a variety of applications in the home. While tropical woods are available from specialty hardwood or flooring retailers, working with native wood allows one to support local foresters, loggers, processors, and independent retailers, and significantly reduce the carbon footprint of the material. And of course, a wide range of finish options are available, to match the function, aesthetic, and indoor air quality needs of any application.
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Earthen or ceramic tile or slate/stone flooring is another attractive option for a floor that is harder and even more durable for high-use environments. Although less comfortable underfoot given its harder composition (similar to concrete), these floors will last a very long time under even the more demanding circumstances and still keep up a beautiful appearance. Again, a solid subfloor is needed for a successful application, but given the thin profile of the stone or tile, a lightweight floor can still be easily achieved. Grout lines can be more difficult to clean than a monolithic floor like concrete or earth, but this can be minimized by using a water-resistant grout for cleaning and by filling the grout lines close to the top of the tile when appropriate. While many tiles may be imported from greater distances or made from high-embodied energy processes, lighter-impact and locally-produced materials may be available. And as mentioned in the roofs section, slate is readily available in the northeast from local quarries and manufacturers. The nature of the material also requires minimal finishing, thus avoiding the need for toxic sealers and finishers.
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Cork/Bamboo/Natural Linoleum
As we get more manufacturer-dependent in our materials, we reach the modern line of natural flooring products. Although generally more expensive and resource-intensive, less supportive of the local economy, and with higher embodied energy and carbon footprint, these modern natural products offer many wonderful features and conveniences. Cork is a fantastic material that offers a wide range of terrific features: moisture-resistant, fire-resistant, anti-microbial, very soft underfoot, lightweight, sourced from a sustainable resource, beautiful, widely flexible in appearance options, insulative for heat loss, sound dampening, and vibration reduction, elastic (resists dents and cracks), and easy to install. Many manufacturers are producing cork flooring panels or tiles with low- or no-VOC binders and finishes. Cork is produced from the bark of the cork oak tree, native to the Mediterranean, ideally in a manner that does not harm or kill the tree. The bark is then refined, processed, and manufactured into ready-to-install glue-applied tiles or floor panels that come in a wide array of colors, patterns, and styles.

Bamboo is a highly-regenerative grass that grows in a wide range of climates; most building-grade bamboo — whether for framing, flooring, wall partitions, or other purposes — comes from larger, tropical species, located primarily in south-east Asia. Similar to cork, the bamboo is harvested, refined, processed, and manufactured, generally into floor strips that install like hardwood flooring, or floor panels. Bamboo has many of the same features and aesthetics of hardwood flooring, while being much more dimensionally-stable (resists warping, bowing, etc.). Formaldehyde-based binders in the laminate product may be a disincentive for the more chemically-sensitive owner.

Natural linoleum is comprised of natural oils, wood dust, rosin, pigments, and natural fibers, and is sold by a number of manufacturers. The colors and patterns can range from subtle and simple to bright and intricate for a seemingly endless variety of appearances, and can be found as either tiles or sheets. Natural linoleum has all the benefits of vinyl flooring — simple to install, easy to clean — but without the off-gassing elements and toxic feedstock and manufacturing by-products.
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Floor Coverings
On top of one's floor, there may be the need for a covering. Whether for thermal improvement, wear reduction, aesthetics, or to accentuate a certain feel in a room, there are as many or more options in floor coverings as there are floors themselves. Many conventional rugs, like carpets, may have off-gassing binders or other additives that will compromise indoor air quality; many will also become host to a variety of microbial — or even macrobial — life forms that will also compromise human health. There are many natural materials available, however, that answer these human occupant-referencing issues, as well as the environmental impact issues further up the pipeline and post-use (disposal). A sampling of natural fiber materials includes sisal, jute, hemp, wool, cotton, and coir. Additionally, there are many post-industrial or post-consumer waste-based recycled products being turned into floor coverings, from fibers to paper to plastics. The texture, functionality, and aesthetic profiles range vastly between these materials; there is a product out there for every purpose.
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