Most patios are made from concrete, cement or asphalt, with chemically treated lumber for borders and steps. These materials’ high embodied energy and the environmentally destructive production practices used to create them are cause for concern. Hard, nonporous cement and asphalt offer undeniable durability, but they also hinder stormwater-runoff absorption and add toxins to your environment during installation.
“The biggest problem with asphalt is one that it shares with concrete and all other forms of continuous-sheet paving: We use too much of it,” says landscape architect Kim Sorvig, co-author of Sustainable Landscape Construction (Island Press, 2000). “This makes very large areas of the earth impervious; increases runoff, erosion and flooding; increases local temperatures by retaining solar heat; and makes these areas inhospitable or deadly to plant and animal life.”
In addition, asphalt’s petroleum content makes it unappealing for use in any living space. “Like any petroleum product, asphalt can be somewhat toxic, and some people are sensitive to its fumes, either during installation or on hot days,” Sorvig says. “Most petroleum products also damage living soils.”
Soil cement—a mixture of Portland cement and local soil—offers an alternative to standard cement mixes. However, the resulting surface presents the same drainage and runoff problems as standard cement surfaces.
“Natural” patio materials can present environmental problems as well. Stone quarrying usually results in scarred landscape and sediment problems in nearby water bodies, and stone dust is hazardous to workers. Lumber and timber products intended for outdoor use routinely are treated with chemicals and pesticides to protect them from insects and weathering. Better choices include “wood” made from recycled plastic.
Fortunately, you can create a hard-surface patio from a variety of materials that help divert waste from landfills. Recycled plastic and rubber paving stones and “bricks” are available in a variety of colors, textures and shapes. Discarded tires also can be cut in half and buried along the edges of patios and footpaths to create rounded borders. Unless they’ve been industrially washed, however, the inside and outside surfaces of old tires are still covered with oil residues. Ask in advance whether they’ve been washed; when you touch the tires, oil should not come off on your hands. Recycled glass, formed into tumbled stones, is another possibility for footpaths and borders.
Brick and stone are also great options. Besides being beautiful and locally obtainable in most areas, they’re durable and re-usable. Like all manufactured materials, brick-making expends energy. Extra-dense landscaping brick requires extra firing to make it harder, which uses even more energy than regular brick-making. And, depending on the materials being used, potentially harmful gases (such as chlorine or fluoride) are emitted during firing. However, once it has cooled, brick becomes inert. Both reclaimed brick and stone are commonly available at construction salvage centers.
Surplus and reclaimed materials from construction sites are great, often-overlooked sources for patio-building supplies. Making use of them—provided they’re not toxic or environmentally detrimental—keeps them from being added to landfills. Check your local listings or the Internet under “lumber,” “building materials” or “construction” for the names of nearby salvers and businesses that sell surplus or salvaged materials.
Weighing your options
When gauging any building material’s sustainability, a crucial element to consider is its embodied energy—the overall amount of energy consumed by locating it, removing it from its source, altering or manufacturing it, transporting it to the site, and installing and maintaining it. “Understand the material’s entire lifecycle,” says Sustainable Landscape Construction co-author Kim Sorvig. “Where does it originate? Set a guideline of using materials that originate within X miles of your site or within the bioregion where you’re located. Find out what’s involved in obtaining the raw material.”
Sorvig suggests you consider whether a material has been processed using toxic materials or is itself toxic, and whether workers’ health was endangered to produce it. Other issues to weigh include how the material was transported from its point of origin to the building location, and if it will be possible to reuse or recycle it should you decide to replace it. “Remember that you’re trying to make a lifecycle analysis and that no product is completely innocent of altering the environment when used in construction,” Sorvig says.
Aggregates (gravel, crushed rock, pebbles)
• Good drainage
• Easy to install
• Low maintenance
• Mining disrupts landscapes; collection of river gravel causes waterway sedimentation
• High energy expenditure for crushing and transportation
Best for: covering medium to large spaces.
• Nontoxic to use
• Reclaimed or salvaged is readily available
• Comes in several colors
• Mining of raw materials, including clay
• Firing uses huge amounts of energy and may produce hazardous gases
Best for: pathways, surface areas, steps between patio levels
Concrete and Cement
• Nontoxic once it's set
• Can be a base for decorative materials such as recycled-glass pieces
• Mining of materials
• High embodied energy during manufacture
• Can burn skin, eyes or lungs while powdered or wet
• May weather poorly if not properly mixed or placed.
• Retains heat
Best for: smaller areas where drainage is not an issue
Recycled-content pavers, bricks, timbers
• Long lasting
• Easy to install
• Splinter free
• Recycled-plastic timbers have limited color selection
• Industrial recycling to melt down old plastics emits toxins.
Best for: edgings, borders, paths and flat areas
• Good use of recycled glass
• Wide array of colors
• Need to be contained within borders
Best for: small spaces such as pathway borders, contained paths and decorative accents
• Natural; wide selection of earth-toned colors
• Reclaimed or salvaged is available online
• Transportation of non-local stones (same from across the globe) uses fuel
• Quarrying destroys ecosystems.
Best for: pathways, terraces, borders, steps between patio levels
Diamond Safety Concepts
recycled-rubber timbers, borders, Eco-flex rubber tiles
Environmental Molding Concepts
recycled-rubber paving tiles
water-permeable, concrete ECO Pavers
Gavin Historical Brick
reclaimed antique brick and cobblestone
Plow & Hearth
recycled-rubber stepping stones
Stoney Creek Materials
recycled, tumbled glass pieces for path borders and landscape accents
interlocking, concrete, porous Eco-Stone pavers