Deconstruction

[edit] Introduction

Deconstruction has been defined as ‘construction in reverse’. As construction involves assembling and erecting buildings, so deconstruction is the complete opposite: it involves taking buildings apart piece by piece, avoiding damage by extracting carefully what is required. This contrasts with demolition which tends to be a relatively arbitrary and destructive process, although generally quicker. Falling materials, noise, nuisance and dust often accompany conventional demolitions, not to mention large amounts of waste.

A building may be deconstructed if it is located in a sensitive area and its demolition would involve danger to the immediate vicinity, or if it has been designed for deconstruction so that its parts can be re-used or recycled.

[edit] Benefits

Deconstruction offers the following benefits compared to demolition:

• Lowers the requirement for extracting virgin resources.
• Can be a cleaner, more environmentally-friendly process with less pollution released into the atmosphere and into water courses.
• Can result in less embodied energy compared to a totally new building.
• Saves energy due to fewer loads transported to site.
• Allows materials to be reused or recycled and so contributes to the circular economy.
• Offers controlled waste management.
• Reused materials from deconstruction can offer a different aesthetic to newly manufactured materials.
• Deconstruction activities tend to be more labour intensive therefore they can provide more jobs locally.
• Less material goes to landfill.

[edit] Why deconstruct?

Deconstruction allows the reuse of materials, which is more environmentally friendly and results in less waste going to landfill – this is critical as construction and demolition waste can comprise up to 20% of all solid waste that ends up in landfills. In addition, some materials may have become more valuable at the time of deconstruction than they were during the original construction, such as some types of brick, decorative cast iron and so on.

When materials are reused/recycled, the resulting building can have less embodied energy and so a smaller carbon footprint. Designing for deconstruction (DfD) requires that designers focus on sustainability, durability and lifecycle analysis, especially when choosing materials and ensuring that the construction process does not render future deconstruction an impractical process. High quality materials integrated into a construction that is as simple as possible can be effective as well as avoiding the use of techniques that rely on nailing and adhesives.

Deconstruction may also keep alive traditional building crafts, such as the use of lime mortars and stone dressings. Furthermore, it can provide opportunities for trainees and apprentices to learn how buildings are put together and to gain skills, such as in basic carpentry, critical thinking and teamwork.

However, not all materials can be salvaged for reuse. Of these, some can be recycled on- or off-site otherwise they may have to be taken to landfill, while hazardous materials, such as asbestos and lead paint, require expert disposal.

Deconstruction tends to be a labour-intensive process given its selective nature. It can take weeks to harvest materials from a structure, whereas demolition can be completed in as little as a day.

A typical deconstruction process involves first removing windows, doors, appliances and finishes from the structure, much of which may be reused or resold. Then the structure is dismantled, usually from the roof, through the middle floors, down to the foundations.

[edit] DfD design principles

Ten common principles of design for deconstruction are:

• Design for prefabrication, pre-assembly and modular construction: prefabricated units are generally easily deconstructed and can be transported in large units. Additionally, modular construction materials allow for large quantities to be transported in one journey.
• Simplify and standardise connection details: this allows for efficient construction and deconstruction and reduces the need for multiple tools.
• Simplify and separate building systems: separating out the distribution systems within non-structural walls can allow for selective removal of low-value components. Consolidating plumbing services will also reduce the lengths of pipe required.
• Consideration of worker safety: the design should aim to reduce potential hazards and the use of potentially hazardous materials.
• Minimise building parts and materials: the design should aim to minimise the number of building materials and the equipment required.
• Select fittings, fasteners, adhesives, sealants etc that allow for disassembly.
• Design to allow for deconstruction logistics: small design tweaks can allow for significant improvements in waste-removal efficiency.
• Reduce building complexity: this will reduce costs and improve buildability as well as simplifying the deconstruction process.
• Design with reusable materials: consideration of materials that are adaptable and will be useful in the future. Materials such as wood, steel members, brick and carpet tiles may be reused or refurbished.
• Design for flexibility and adaptability: the design should consider any future renovations or adaptations that may be required to extend the life of the building.

[edit] Timber

Timber lends itself to easier reuse than say, brick, stone or metal. The benefits of avoiding timber waste mean fewer disposal costs, a reduction in greenhouse gas emissions (methane) from decomposition. The process typically has a 33% efficiency rate: it is estimated that every three square-feet of deconstructed timber will yield around one square foot of new timber construction.

[edit] Related articles on Designing Buildings Wiki

• Building pathology.
• Building Revolutions - review.
• Circular economy.
• Circular economy in the built environment.
• Climate Change Act.
• Cradle to cradle product registry system.
• Decommissioning.
• Design for deconstruction.
• Design for deconstruction, BRE modular show house.
• Design for deconstruction, office building.
• Design for deconstruction, ski slope.
• Dismantling.
• Disposal.
• Emission rates.
• End of life potential.
• Energy targets.
• Examining the 2021 construction materials shortage.
• Forensic engineering in developing countries.
• Kit house.
• Lean construction.
• Mean Lean Green.
• Modular buildings.
• Off-site prefabrication of buildings: A guide to connection choices.
• Prefabrication.
• Recyclable construction materials.
• Site waste management plan.
• Structure relocation.
• Structures at the end of their design life.
• Sustainability.
• Sustainable materials