Tuesday, March 24, 2009

Concrete, Stone, Terrazzo


Floors for the ages

Floors made of tile, concrete, and stone are long-lived and perfect for some kinds of healthy green homes. Here's a materials primer to help you decide whether they are a good choice for you.

Ceramic and porcelain tile are made primarily from clay, an abundant although nonrenewable natural resource. Although the manufacturing process is energy intensive, tile is nontoxic and easy to clean if the grout is sealed. If a tile ever cracks, it can be chiseled out and replaced. (Quick tip: buy extra tiles initially to make replacement easy.)
Concrete, Stone, Terrazzo, and Tile Floors

Concrete floors have crossed over from industrial buildings to stylish homes. The concrete can be colored, stained or patterned for a one-of-a-kind look. The finished floors are durable, easy to clean, and compatible with radiant floor heating systems and passive solar design. However, concrete is prone to cracking. Some people think that adds character to the floor but if you can't live with cracks, then concrete isn't for you.

Stone floors are about as natural as you can get, but that's not to say they're without environmental impacts. Digging stone out of the earth can damage wildlife habitat and scar landscapes. Although the stone for floors is minimally processed, it's a heavy and bulky material that takes a lot of energy to transport. It may be quarried in one part of the world, shipped to another for cutting and polishing, and to yet another to a wholesaler or retailer before it makes its way into your home. On the other hand, stone floors can last for generations.

Traditionally a mix of marble or other stone in a matrix of concrete, terrazzo is making a comeback because of consumers' interest in recycled materials. A few companies have started making floors with poured-in-place terrazzo and terrazzo tiles using a high percentage of recycled glass set in concrete or epoxy. The slurry is poured onto a subfloor, smoothed and allowed to cure, then ground to a smooth polish. Although expensive at about $15 a square foot (plus installation), terrazzo is also becoming popular for countertops, tub enclosures, and backsplashes (the protective panels behind sinks and stoves).

Top Tips

At home

  • Listen up! Hard-surface floors can be noisy especially in homes with open floor plans. They can also be hard on joints (and dropped dishes). They can feel cold underfoot unless used as part of a passive solar design or with radiant floor heating.

When shopping, look for materials that are

  • Local and recycled. Choose products extracted and manufactured within 500 miles of your home or salvaged from a building in the area. If it's terrazzo you're after, find a product with high recycled content. In the case of recycled-content tile, some manufacturers are just recycling their own waste, but a few companies use post-consumer recycled content.

  • Healthy for your home. When installing tile or stone, use zero- or low-VOC (volatile organic compound) tile-setting adhesives, grouts, and sealants. In the case of stone, check with the supplier about whether it requires sealing to prevent staining; if it does, ask about low- or zero-VOC sealants.

  • Made specifically for floors. When choosing tile, stone or terrazzo, make sure it's a product designed for floors, with a nonslip finish.

Other Considerations

A concrete floor makes the most sense for new homes that are built on a slab that can do double duty as the finish floor. This reduces your use of materials (you're not adding extra material, like wood or carpet, on top of the slab) but it does require protecting the slab during construction. In existing homes, a thin concrete floor can be poured over a wood subfloor if there is sufficient structural support. For installation, use an experienced concrete floor specialist. If using acid-based stains on the concrete, be aware that they are noxious when installed (although inert when dry). Use water-based, low- or no-VOC sealants.


...to your wallet
These materials cover the budget gamut, from $2 a square foot for the cheapest ceramic tiles to $35 a square foot for glass tiles and rare stones. Labor costs are usually higher than for other types of flooring. But these products can easily last as long as the home. So their cost over the lifetime of the flooring may be lower than that of flooring that is less durable and harder to maintain.

...to the Earth
Some concrete is made with recycled fly ash, a powdery byproduct of coal-burning electric power plants. While tile and traditional concrete take a lot of energy to manufacture, concrete made with fly ash keeps waste out of landfills and reduces air pollution and global warming impacts.

Common Mistakes

  • Covering the mass. If your home was designed for passive solar heating, you may have tile, stone, or concrete floors. These materials have a high thermal mass, which means they moderate temperatures in the home by storing the sun's heat during the day and releasing the heat at night when temperatures cool. Don't put carpeting or rugs over thermal mass floors if they're part of a passive solar design; the thermal mass won't be able to do its job.

  • Sinking the subfloor. These floors can be heavy. Make sure the subfloor can bear their weight. If in doubt, consult a flooring installation specialist.

Getting Started

  • Search our site for local concrete and terrazzo flooring specialists. Visit tile and stone dealers in your area and ask about locally quarried or salvaged stone and locally manufactured, recycled-content tile.

  • Ask any potential installer the following questions:

    • How much expertise does the flooring contractor have installing the type of floor you selected?

    • Ask to for references, but also try to visit a few homes where the contractor has installed the same type of flooring that you've chosen. Check the quality of the installation as well as how well the material has held up.

    • If any adhesives, stains, sealants, mortar, or grout will be used during the installation, ask about low- or zero-VOC options. If you meet resistance to using low-VOC products, consider shopping around for a contractor who has experience with healthy home practices.

  • For general advice on what questions to ask contractors and other tradespeople, see our "What to Ask Your Contractor" article.

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