As we look toward a future with mandatory green building ordinances in California and elsewhere, one critical construction component is often overlooked - - site preparation. Regardless of the property – whether there is a pre-existing structure or simply an open field – site preparation typically signals the start of the actual construction process.
Deconstruction vs. demolition
The conventional way to bring down a building is the good ol’ wrecking ball. The building is collapsed into a huge pile of rubble and then transferred to debris dumpsters. All materials are lumped together, many of which take several generations to decompose: steel 100 years, aluminum 300 years, plastic 450 years. Glass never decomposes. Then there is the hazardous waste: who knows what harm lurks there? In short, this conventional, commingled trash heap isn’t going anywhere soon. No matter the nature of the material, it is all going to the same place – to be landfill forever.
There is a better way.
Deconstruction is quickly becoming the “green” site preparation alternative. Sure it takes a little more planning and coordination; but with some foresight and creativity, landfill becomes the very last option for construction debris. There are even environmental non-profits, like Deconstruction & Reuse Network, offering tax benefits for property owners’ green efforts.
Deconstruction process
Deconstruction has two distinct phases. First is the soft-strip: the structural interior and exterior are scoured for reusable and recyclable materials. Reuse should always be the paramount goal, whether the materials are to be reused on-site as part of the new project or integrated somewhere off-site. During this phase, items like reclaimed wood, brick, rock and reusable or recyclable fixtures and furniture are extracted. By the time this first phase is complete, there should be nothing much left but the structural envelope, that is, the walls, roof, foundation and supporting members.
The envelope is demolished in the second phase. Here, all the remaining debris is site-sorted, meaning things like rebar are separated from concrete, clean wood studs from drywall, lathe from plaster. Once demolition is complete, there is an assortment of piles -- clean wood, drywall, metal. All materials from both phases are parceled out and inventoried. These materials are then transferred by material type to a reuse or recycling facility for processing.
How to get started
Planning a project that should involve looking at deconstruction? Bob Falk & Brad Guy wrote “Unbuilding: Salvaging the Architectural Treasures of Unwanted Houses” (Taunton Press, 2007) is a great primer on the process that can be used to start planning the deconstruction of any type building.
Also check out the California Building Standards Commission’s new CALGreen standards. They are voluntary now, but -- come January 2011 -- they will be mandatory.
Not sure what to do with your construction debris, CalRecycle is a great starting point.
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