Designing Against The Grain: The emergence of rice flooring

by Elaina Adams | September 1, 2011 8:29 am

[1]

By Tamar Royt, BA, LLB (JD), MBA
A relatively new product in the construction industry, rice husk-based materials are rapidly becoming a viable replacement to hardwoods for outdoor flooring, cladding, and fencing. Aside from the environmental benefits of saving forests by reusing rice husks (a waste product difficult to dispose of), rice husk has unique properties that make it more stable and resilient than hardwoods.

With esthetic developments in recent years, rice-based materials are becoming increasingly visually appealing and almost indiscernible from natural wood. With a growing list of successful applications in Europe and North America, rice-based materials are likely to become commonly used within the next five years as more innovations are developed. For now, it is increasingly being used as a replacement for exotic hardwoods such as ipe and teak, particularly for outdoor areas.

A plentiful grain with unique qualities
Husks (also known as ‘hulls’) are the hard, protective coverings that shield the grain during the growing season. For every tonne of rice produced, one quarter tonne of rice hulls are left behind. (For additional information, see www.recycledrice.org[2]). Once ready for consumption, the hull is removed from the rice and becomes a waste byproduct.

[3]

When one considers annual worldwide rice production is estimated at 680 million tonnes, it becomes clear these husks are plentiful. (See www.wikipedia.com[4]). Mostly indigestible to humans or animals, rice husk is made of hard materials, including opaline silica, and lignin. Burning the hulls is incredibly difficult as rice husk is impenetrable and slow to burn. This is despite the fact it is primarily a very ‘dry’ product with a very low moisture level. Ironically, all these so-called difficulties with disposing of rice husk make the material ideal for building products.

Firstly, it is precisely because of its unattractive qualities as a food source that it lends itself so well to construction. As no living organism can obtain nutrients from it, it essentially acts as a repellent to termites. Further, rice hulls are a Class A insulating material because they are difficult to burn. Finally, because of its low moisture content (MC), this material is less likely to allow moisture to propagate mould or fungi.

According to Paul A. Olivier, PhD, a recycling engineer who built the first modern house (Washington, La.) using rice hulls as insulation, the materials are unique within nature. They contain about 20 per cent opaline silica in combination with a large amount of the phenyl propanoid structural polymer called lignin. It is unusual as a cereal byproduct as the husks are incredibly low in both protein and carbohydrates (hence its poor nutritional value and lack of appeal to termites), yet incredibly high in crude fibre. Of all the cereal byproducts, the rice hull has the lowest percentage of digestible nutrients. (See B. Juliano’s Rice: Chemistry and Technology, p.695 [1985]).

ASTM testing conducted by consulting and testing company R&D Services (Cookville, Tenn.) (For more information, see “The Rice Hull House” by Paul A. Oliver, PhD. Visit www.appropedia.org/Rice_Hulls_in_Construction[5]).revealed rice hulls:

• do not easily flame or smoulder;
• are highly resistant to moisture and fungal decomposition;
• do not transfer heat very well;
• do not smell or emit gases; and
• are not corrosive with respect to copper, steel, or aluminum.

According to the National Electrical Manufacturers Association (NEMA), in their raw and unprocessed state, rice hulls constitute a Class A or Class I insulation material. Therefore, testing concluded they can be used economically to insulate walls, floors, and roof cavities.  As insulation, rice hulls are essentially fireproof and have a thermal resistance of about R-3 per inch (0.5 RSI) and make for a great vapour ‘buffer.’

[6]

Construction experience
In Asia, inroads have been made for mixing rice husks with plastics to build low-cost homes. With the National Research Council of Canada Institute for Research in Construction (NRC-IRC), a Canadian company had developed different rice husk and wood-plastic composites (WPCs) that use either recycled or ‘virgin’ unused plastic. (See “Rice Husk Panels Turn Waste into Wall: A Housing Idea from the World’s Most Consumed Grain,” from September 25, 2007, by CanWest MediaWorks Publications).

There are several methods used to convert rice husk into building materials. Most, if not all, involve some use of plastics—either polyvinyl chloride (PVC) or polyethylene. Some manufacturers use recycled polyethylene (sometimes in combination with glass spheres), while others rely on PVC as it is longer lasting and more durable. Both methods claim environmental advantages for the use of their plastic of choice. Although polyethylene may be recycled, it is not as durable and long wearing as PVC. The environmental disadvantage of PVC, however, is it is difficult to dispose of. On the other hand, the argument is made that the objective of a construction product is to be indestructible, and building a long-wearing and durable material is key to avoiding waste and so some prefer the PVC component.

Esthetic appeal
As established, rice husk and, in particular, rice composite products, have been under development and some have been used for more than a decade. However, it is the recent developments and improvements in the look of composite rice that have led to the rising popularity of this material in architectural finishes.

A German outdoor furniture manufacturer has been redefining the use of composite rice in materials in applications where strong esthetic appeal—not just durability and strength—is critical. Teak is a commonly used material in furniture construction, but although considered a durable wood, teak is far from perfect. Prone to fading in harsh sun and somewhat susceptible to rotting and splintering, teak presented several problems, particularly in markets where the long summer and bright sun took its toll (e.g. South Africa and Australia).

[7]

Sharp fluctuations in price and availability further urged the quest for an alternative product. Out of their facilities in the Far East, the manufacturer assigned a team to find a viable alternative—several reiterations (spanning close to a decade) were needed to come up with a product that appeared natural and could be handled like wood. The result was a very wood-like looking material that, despite being completely wood-free, could be cut, sanded, stained, and refinished, or left natural and untreated, to create various pieces. Rice husk was blended, extruded, and treated to produce a natural material in appearance. Unlike wood composite products, rice products are not prone to fading.

Additionally, while many WPCs come pre-stained, ‘new-generation’ rice-based products are sold unfinished and can be worked like real wood. If electing for a stain, it is important to test the stain first. Since the rice material is essentially non-porous, one must ensure the stain properly adheres to the material. Specific formulations for rice products are available in various colours.

Using rice husk in decking and cladding
Given its unique structural advantages, as well as the tremendous esthetic appeal of some products, rice decking and wall cladding applications are becoming increasingly more prevalent throughout North America in various climates. Decking applications typically require runners to be pre-installed so as to allow for proper drainage. As rice hulls are fairly moisture-free, expansion and contraction of wood-free products tends to be minimal (if at all), so planks can be installed very close to each other with very little spacing. (When the rice-based product also incorporates composite wood, expansion, contraction, and fading may be more pronounced.)

[8]

Wall cladding
In addition to deck installation, rice-based materials may be used for wall cladding. Installation is typically done over pre-installed rods but will differ greatly based on use and application. Typical details will also vary greatly depending on design. Generally, pieces come in left, right, and corner profiles.

Installation near pool areas
Certain rice-based decking materials have been found to be extremely skid-resistant and therefore ideal for installation near pools or wet areas.

Stairs
Using decking planks, panels, or a combination of both, stairs can be constructed to fit any customized area.

[9]

General information
The following instructions are obtained from a specific manufacturer of rice decking product and are intended for a general reference only. This installation applies to site- finish rice decking products. For installation instructions on any specific product, the designer must consult that manufacturer’s documentation.

1. Decking should be installed by an authorized professional.
2. One should ensure a slope of approximately two degrees for adequate water drainage. If ponding water freezes around decking or joists it can cause damage.
3. Allow for temperature-dependent linear expansion as indicated by the manufacturer.
4. Only use construction fastening material and hardware suitable for outdoor use (e.g. stainless steel screws).
5. When using screws, pre-drill the product on a flat surface. One only needs to drill the first plank installed, and screws can be hid effectively with a dowel.
6. Consider local building codes as well as the installation instructions and technical information.
7. To ensure the necessary stability, the joists should typically be applied at a maximum distance of 406 mm (16 in.), ensuring a maximum overhang of 25 mm (1 in.) at the ends.
8. The concrete base or suspended substructure onto which the runners are fixed must be stable. Where cement is used, ensure adequate drying time for the cement to stabilize and harden.

(This normally takes about five days for non-quick-drying cement.)

• When butting the planks, one joist should be used for each clip; therefore, double runners should be installed where the planks are butted.
• When installing planks next to each other, gently tap planks into place. Each one needs to be fixed with a clip on the joist.
• The end plank should be fixed with a screw and dowel.

Applying ‘glaze’

1. Before applying a glaze finish or sealer, remove stains or harsh dirt marks with sandpaper. Use sandpaper with grit between
   24 and 60 max.
2. After sanding, remove all dust.
3. For details on applying one’s preferred surface finish, follow the appropriate application instructions provided by the manufacturer.
4. Apply surface finish in the gaps with a small brush.
5. Important: As rice hull material is particularly impenetrable, it is highly recommended one tests any stain before undertaking a complete application. This is done to observe if and how the stain will adhere to the material.

Conclusion
Rice hulls have proven to be a technically and environmentally beneficial material with over a decade of successful application in various forms of construction. It is recent improvements in the esthetic appeal of rice-based materials, however, that will lead to the continued commercial success of rice hulls in various aspects of construction.

Tamar Royt, BA, LLB (JD), MBA, is the founder and president of Toronto-based Silverwood Flooring, a provider of flooring products to the design and construction industry. Since 2005, she has been working with leading developers, architects, and designers to introduce well-designed, environmentally responsible flooring to the Canadian market. Royt is ranked on the Profit W100: Canada’s Top Women Entrepreneurs and is a contributing member of several industry associations, including the National Wood Flooring Association (NWFA), Canada Green Building Council (CaGBC), Association of Registered Interior Designers of Ontario (ARIDO), Ontario Retirement Communities Association (ORCA), and the Building Industry and Land Development Association (BILD). She can be contacted via e-mail at tamar@silverwoodflooring.com.

Source URL: https://www.constructioncanada.net/designing-against-the-grain-the-emergence-of-rice-flooring/

---