Deconstruction (building)


In the context of physical construction, deconstruction is the selective dismantlement of building components, specifically for reuse, repurposing, recycling, and waste management. It differs from demolition where a site is cleared of its building by the most expedient means. Deconstruction has also been defined as “construction in reverse”. Deconstruction requires a substantially higher degree of hands-on labor than does traditional demolition, but as such provides a viable platform for unskilled or unemployed workers to receive job skills training. The process of dismantling structures is an ancient activity that has been revived by the growing field of sustainable, green method of building.
When buildings reach the end of their useful life, they are typically demolished and hauled to landfills. Building implosions or ‘wrecking-ball’ style demolitions are relatively inexpensive and offer a quick method of clearing sites for new structures. On the other hand, these methods create substantial amounts of waste. Components within old buildings may still be valuable, sometimes more valuable than at the time the building was constructed. Deconstruction is a method of harvesting what is commonly considered “waste” and reclaiming it into useful building material.

Contribution to sustainability

Deconstruction has strong ties to environmental sustainability. In addition to giving materials a new life cycle, deconstructing buildings helps to lower the need for virgin resources. This in turn leads to energy and emissions reductions from the refining and manufacture of new materials, especially when considering that an estimated 40% of Global material flows can be attributed to construction, maintenance, and renovation of structures. As deconstruction is often done on a local level, many times on-site, energy and emissions are also saved in the transportation of materials. Deconstruction can potentially support communities by providing local jobs and renovated structures. Deconstruction creates 6-8 Jobs, for every 1 created by traditional demolition. In addition, solid waste from conventional demolition is diverted from landfills. This is a major benefit because construction and demolition waste accounts for approximately 20% - 40% of the solid waste stream. 90% of this construction and demolition waste stream is generated during the process of demolition. In 2015 548 million tons of Construction and demolition waste were created in the United States alone.
Deconstruction allows for substantially higher levels of material reuse and recycling than does conventional processes of demolition. Up to 25% of material in a traditional residential structure can be readily reused, while up to 70% of material can be recycled.

Benefits of avoiding wood waste

In Canada, the CO2 Neutral Alliance has created a website with resources for regulators and municipalities, developers and contractors, business owners and operators, and individuals and households. Benefits for municipalities include:
Improving the local environment and overall sustainability of your community
For every three square feet of deconstruction, enough lumber can be salvaged to build one square foot of new construction. At this rate, if deconstruction replaced residential demolition, the United States could generate enough recovered wood to construct 120,000 new affordable homes each year. The deconstruction of a typical wood frame home can yield 6,000 board feet of reusable lumber.
Every year the United States buries about 33 million tons of wood-related construction and demolition debris in landfills. As anaerobic microorganisms decompose this wood, it will release about five million tons of carbon equivalent in the form of methane gas.

Typical methods of deconstruction

Deconstruction is commonly separated into two categories; structural and non-structural. Non-structural deconstruction, also known as “soft-stripping”, consists of reclaiming non-structural components, appliances, doors, windows, and finish materials. The reuse of these types of materials is commonplace and considered to be a mature market in many locales.
Structural deconstruction involves dismantling the structural components of a building. Traditionally this had only been performed to reclaim expensive or rare materials such as used brick, dimension stone, and extinct wood. In antiquity, it was common to raze stone buildings and reuse the stone; it was also common to steal stones from a building that was not being totally demolished: this is the literal meaning of the word . Used brick and dimension limestone, in particular, have a long tradition of reuse due to their durability and color changes over time. Recently, the rise of environmental awareness and sustainable building has made a much wider range of materials worthy of structural deconstruction. Low-end, commonplace materials such as dimensional lumber have become part of this newly emerging market.
The United States military has utilized structural deconstruction in many of its bases. The construction methods of barracks, among other base structures, are usually relatively simple. They typically contained large amounts of lumber and used minimal adhesives and finish-work. In addition, the buildings are often identical, making the process of deconstructing multiple buildings much easier. Many barracks were the era prior to WWII, and have aged to the point where they now need to be torn down. Deconstruction was deemed very practical due to the abundance of labor the military has access to and the value of the materials themselves.
Natural disasters, such as hurricanes, floods, tsunamis, and earthquakes often leave a vast amount of usable building materials in their wake. Structures that remain standing are often deconstructed to provide materials for rebuilding the region.

Economic potential

Deconstruction's economic viability varies from project to project. The amount of time and cost of labor are the main drawbacks. Harvesting materials from a structure can take weeks, whereas demolition may be completed in roughly a day. However, some of the costs, if not all, can be recovered. Reusing the materials in a new on-site structure, selling reclaimed materials, donating materials for income tax write-offs, and avoiding landfill “tipping fees” are all ways in which the cost of deconstruction can be made comparable to demolition.
Reclaiming the materials for a new on-site structure is the most economically and environmentally efficient option. Tipping fees and the costs of new materials are avoided; in addition, the transportation of the materials is non-existent. Selling the used materials or donating them to non-profit organizations are another effective way of gaining capital. Donations to NPO's such as Habitat for Humanity’s ReStore are tax-deductible. Many times it is possible to claim the value to be half of what that particular material would cost new. When donating rare or antique components it is sometimes possible to claim a higher value than a comparable, brand-new material.
Value can also be added to new structures that are built by implementing reused materials. The United States Green Building Council's program entitled Leadership in Energy and Environmental Design offers seven credits relating to reusing materials. These include credits for building-shell reuse, material reuse, and diverting waste from landfills. Building shell-reuse is particularly appropriate for shells made of dimension stone.
Deconstruction is well suited to job training for the construction trades. Taking down a building is an excellent way for a worker to learn how to put a building up. This is vital for the economic recovery of inner-city communities. Unskilled and low-skilled workers can receive on-the-job training in use of basic carpentry tools and techniques, as well as learning teamwork, problem-solving, critical thinking and good work habits.

Process

When choosing to deconstruct a building there are some important aspects that need to be taken into consideration. Developing a list of local contacts that are able to take used materials is an essential first step. These might include commercial architectural salvage businesses, reclamation yards, not-for-profit and social enterprise salvage warehouses, and dismantling contractors. Materials that cannot be salvaged may be recycled on-site or off-site, or taken to landfills. The next step involves identifying which, if any, are hazardous materials. Lead paint and asbestos are two substances in particular that need to be handled extremely cautiously and disposed of properly.
Salvaged goods that are contaminated with hazardous materials such as Lead Paint will need additional processing in order to be reused again, which adds an additional cost barrier to the effective reuse of certain materials reclaimed in a deconstruction project. To address this challenge, some deconstruction contractors have begun utilizing specialized sealed processing trailers that utilize Negative Pressure to provide on-site lead remediation processing for salvaged timber.
The following set of questions can aide in developing a deconstruction plan:
It is common practice, and common sense, to “soft-strip” the structure first; remove all appliances, windows, doors, and other finishing materials. These will account for a large percentage of the marketable components. After the non-structural deconstruction, structural is the next step. It is best to start at the roof and work down to the foundation.
Building components that are dismantled will need to be stored in a secure, dry location. This will protect them from water damage and theft. Once separated from the structure, materials can also be cleaned and/or refinished to increase value. Building an inventory list of the materials at hand will help determine where each item will be sent.

Designing for deconstruction (DfD)

"The end of the building’s useful life generates a stream of used materials that can be reprocessed for new construction. The selection of materials for reuse or recycling should not start at the end of the building’s life cycle, it should start at the design stage. Architects and engineers should keep the whole life cycle of the building in mind and select construction materials based on their capacity to be reused or recycled after the building has served its purpose."
An upstream approach to deconstruction can be implemented into buildings during their design process. This is a current trend in sustainable architecture. Often, simple construction methods combined with high-grade, durable materials work best for DfD structures. Separating layers of a building's infrastructure and making them visible can significantly simplify its deconstruction. Making components within systems separable also assists in being able to dismantle materials quickly and efficiently. This can be achieved by using mechanical fasteners such as bolts to connect parts. Allowing physical access to the fasteners is another needed aspect of this design. Also, it is important to use standardized materials and assemble them in a consistent manner throughout the project.
Consolidation of Plumbing, HVAC, and other utility service points within a building has the benefits of reducing the need for long service lines, but also reduces points of entanglement and conflict with other building elements. Similarly, utilizing raised floor or dropped ceiling methods create easier access to mechanical and electrical services, and can reduce the time-needed to remove these components during the process of deconstruction.
Some conventional construction methods and materials are difficult or impossible to deconstruct and should be avoided when designing for deconstruction. The use of nails and adhesives significantly slows down the deconstruction process and has a tendency to ruin otherwise reusable materials. Avoid hazardous materials altogether as they are detrimental to the natural environment and are non-reusable. Using mixed material grades makes the process of identifying pieces for resale difficult.
Some commercial buildings that have been designed utilizing DfD principles utilize built in anchor points and other features intended to provide additional fall protection options. Such design considerations can increase overall worker safety, and decrease amount of overall time spent on deconstruction.
Deconstruction is important for more than just the end of a building's life-cycle. Buildings that have been designed with deconstruction in mind are often easier to maintain and adapt to new uses. Saving the shell of a building or adapting interior spaces to meet new needs ensures that new structures have a small environmental impact.
An alternative worth considering is modular building, like the Habitat 67 project in Montreal, Quebec, Canada. This was a residential structure consisting of separate, functional apartments that could be put together in a variety of ways. As people moved in or out, the units could be reconfigured as desired.