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4. Deconstruction

Deconstruction is the reverse of construction - removing building parts in the reverse order to construction.

Sustainable site clearance methods to reduce the amount of waste that ends up in landfill during development should be encouraged.

BRANZ suggests the prioritisation of building relocation and deconstruction over demolition, wherever possible.

🡒 Relocation involves the transportation of existing houses from development areas and providing them for alternative uses, such as selling them as an affordable home, gifting them to groups who have the ability to refurbish them.

🡒 Deconstruction is a way of breaking down building materials for reuse and recycling. By making reuse a key focus it requires more sorting of materials, but also minimises the need for expensive, and noisy, heavy machinery like diggers.

🡒 Demolition is the process of dismantling existing buildings. Buildings are demolished as a building has reached the end of its serviceability, its structural integrity has been compromised or when contaminants are found to be present, or when fire damage has occurred.

Planning for deconstruction

The amount of material that can be salvaged for reuse or recycling is largely dependent on the type of building being deconstructed, time constraints and the local recycling market.

Good planning will help to improve salvage and reduce waste.

Planning for deconstruction includes:

  • undertaking an initial assessment of the site and building to determine whether the building will be a good candidate for deconstruction - this includes assessing the cost-benefit of deconstruction versus demolition
  • developing an inventory of materials and finding out what materials are recyclable or reusable and, if possible, arranging prior sales for salvaged and recyclable material
  • developing a deconstruction plan
  • training staff and subcontractors prior to working on site to maximise the volume and quality of materials salvaged

Initial assessment of site and building

An initial assessment of the building and the site will help identify salvage opportunities. At this stage, consider whether to sell the whole building or dismantle and sell individual parts.

Types of buildings likely to be good candidates for removal for reuse are structurally sound (i.e. generally weathertight to minimise rotted and decayed materials, and with minimal borer damage) and able to be removed from the site (protected trees or other buildings may hinder removal).

Examples of buildings that currently have a market for reuse include greenhouses, steel-framed warehouses, temporary buildings and houses that are good specimens such as timber-framed villas.

Types of buildings likely to be good candidates for deconstruction

  • timber framed with heavy timbers and beams or with unique timbers
  • constructed with specialty materials such as native or hardwood flooring or wall timbers, multi-paned windows, architectural mouldings and unique doors or plumbing/electrical fixtures
  • constructed with high-quality brick laid with low-quality mortar to allow relatively easy break-up and cleaning
  • commercial buildings constructed using high-quality reusable items such as steel beams and steel cladding
  • some types of concrete tilt-slab construction

Paperwork review

A review of paperwork to determine types of materials, construction techniques and the location of all services is a good place to start. Review plans, working drawings and engineers' reports obtained from your city or district council or from your client. The architect or engineer may have already prepared a deconstruction plan that includes a list of building materials and components (as well as their design or service life and the best options for reuse, refurbishment or recycling) and instructions on how to deconstruct elements.

Site survey and building assessment

A survey of the site should be made to determine whether the building will be removed for reuse or deconstructed and to identify salvage opportunities and hazardous materials.

Consider involving some of the following people in the building assessment:

  • builder, carpenter, architect or anyone with expertise in the methods and materials of construction
  • tradesperson experienced in repair/restoration of equipment, appliances or materials
  • structural engineer/materials inspector who can provide information on the structural integrity of building components and/or the existence of hazardous materials requiring special handling
  • someone who has a good understanding of the salvage value of building materials in the local market
  • the client and/or the design team may also want to be part of the assessment



Tools you'll need to perform a building assessment include:

✔️ Inspection forms - to ensure that you have collected all the information you need

✔️ Camera - photographs can be helpful in recalling important characteristics of the building and the site

✔️ Hand/power tools - it may be useful to look behind walls or beneath flooring to verify the size and condition of structural components or the existence of hazardous materials

✔️ Respirators or dust masks - these should be worn whenever any cutting, drilling or removal of materials is done

Inventory of materials

Document the following information using the REBRI waste minimisation plan:

  • develop an inventory of types and quantities of materials to be salvaged, recycled or disposed of and determine markets for materials prior to the project starting
  • determine costs and savings associated with reuse, recycling and disposal. Make sure you include payment for recyclables and reusable materials, reduced landfill/cleanfill disposal costs, transport costs and time required for sorting or preparing materials for reuse or recycling
  • identify components from the old building for reuse in the new building. Compile a detailed list to pass to relevant contractors
  • photograph joinery and other building components in place prior to removal to indicate potential reuse and to give purchasers a better idea of how the joinery would look in place

Deconstruction scheduling

The amount, type and condition of materials salvaged is affected by the time available to do the work and the methodology and sequencing of deconstruction. To maximise recovery rates and avoid contaminating or damaging materials (which then precludes reuse), it is important to:

  • use plans and working drawings to help determine how to deconstruct using reverse construction sequencing
  • ensure adequate time is scheduled for deconstruction methods
  • explain to clients that, because deconstruction involves careful planning and preparation and is more labour intensive than demolition, more time is required

Deconstruction plan

Have a plan for the project that aims to maximise resource recovery.

Collate all the deconstruction planning work into the REBRI waste management plan or adapt it to your own business. The plan can then be used when tendering for contracts and to provide staff with information on the project and can be included as part of the application for a building consent, which is required for demolition of all buildings in New Zealand.

The plan should include:

  • quantities of materials to be salvaged for reuse, recycled or sent for disposal
  • destination and/or intended end use of the building's various components, including appropriate disposal of residual waste
  • deconstruction methodology and sequencing
  • schedule for deconstruction
  • location, security and protection of storage areas (if materials are to be stored on site) - clearly mark location of all storage areas on a site plan if this is available
  • details of materials handling and removal procedures, particularly on project sites with space constraints


Training staff and subcontractors

Training demolition staff and subcontractors is a key success factor for high recovery of building components. By understanding the process of transforming demolition materials into valuable products, workers take more care in recovering as much material as possible while ensuring minimal contamination. Most training in the industry is done on the job, so your training programme should reflect this.

Consider these things:

  • ensure employees and subcontractors are aware of what they need to do and how they should do it. Consider providing documentation on resource recovery requirements, deconstruction techniques and sorting and storage requirements
  • formalise the roles of senior staff as trainers and provide any training to enable them to be more effective on-the-job trainers
  • emphasise the benefits of deconstruction and maximising resource recovery
  • ensure accurate identification and planning for hazardous substances - the increased manual nature of deconstruction means that this is even more important. Occupational health and safety advisors may be able to assist
  • consider using a formal job training programme through industry training organisations and/or apprenticeships
  • consider the mix of staff experience on any project to ensure less-experienced staff are mentored and managed by more-experienced staff
  • check documentation regularly and keep a record of training

Dismantling and deconstruction

Deconstruction techniques remove building components piece by piece rather than damaging building parts by destructive methods. Start with the soft strip of interior fittings, doors and linings then remove the roofing, cladding, windows and finally framing and foundations. Multi-storey buildings are typically deconstructed floor by floor, beginning with the roof and upper floor.

  • prepare the site and mark out waste storage areas before dismantling begins to make the process smoother and help reduce damage to salvaged materials. Increased space for storage of materials is likely to be needed for deconstruction versus demolition
  • undertake the soft strip manually with hand tools to minimise damage caused by large machinery
  • during the hard strip, dismantling of major components may be done in stages. Large-scale removal of building parts such as flooring or roofing may be done initially with excavators or cranes followed by more detailed separation of components and contamination by hand (on site or off site). Preparation of materials may be required prior to removal, such as soaking timber floors and fittings with water to avoid splitting

What products can be salvaged?

Most items recovered from existing buildings can be reused or recycled into usable materials. The method of building removal determines whether a building becomes waste or provides building materials for reuse. Traditional demolition methods can produce a lot of waste by destroying the component parts.

Deconstruction - careful and selective dismantling and separation for reuse and recycling - reduces the volume of waste disposed to landfill and cleanfill and allows the removal of components in a form that can easily be reused.

Most buildings that have reached the end of their desired life or are undergoing renovations have materials and systems that still have some useful life.

Doors and windows

  • doors, aluminium steel or timber - reuse with full frame and hardware or remove the glass, recycle the frame and reuse the glass. (Old doors and windows may be reused in small garden sheds and similar buildings but BRANZ does not recommend their reuse in buildings that require building consent and/or are used for human habitation)
  • overhead doors - reuse (springs can have a short lifetime, so replace these)
  • mechanical closers - reuse
  • panic hardware - reuse
  • Unframed glass mirrors - reuse
  • Store fronts - reuse, best to be kept in one unit
  • Glass from windows and doors - reuse
  • Timber or metal from frames - recycle

Electrical and plumbing fixtures and fittings

  • baths, sinks, toilets - reuse
  • taps - reuse, metal is recyclable
  • switches - reuse
  • light fittings - reuse
  • service equipment - reuse stoves, heaters, air conditioners; all metal components recyclable
  • wiring - recycle without insulation

Hazardous materials

In the interests of health and safety, you should check the removal and disposal requirements of hazardous materials with your city or district council. Hazardous wastes from demolition of buildings include:

  • fluorescent light ballasts manufactured prior to 1978 - contain polychlorinated biphenyls (PCBs)
  • fluorescent lamps - contain mercury
  • refrigeration, air conditioning and other equipment that contains refrigerants made using Chlorofluorocarbons (CFCs)
  • batteries - contain lead, mercury and acid
  • paints, solvents and other hazardous fluids
  • asbestos-based materials – removing asbestos from a building or site is covered by government regulations. Find more details from Worksafe
  • materials with lead-based finishes

Insulation

Old insulation may be reused in renovation work, such as adding insulation under the floors or in the roof spaces of existing buildings that have none. Reusing old insulation in new building work is not recommended because its R-value may not be known and building consent authorities may be unwilling to accept it as Building Code-compliant.

  • fibreglass/mineral wool/polyester batt insulation - reuse
  • rigid fibreglass insulation - reuse
  • polystyrene rigid insulation - reuse, metal part of sandwich panel is recyclable
  • loose-fill chip/pellet/shreds - reuse

Linings and finishings

  • carpet/carpet tiles - reuse for original purpose or for planting projects, recycle
  • terracotta tile - reuse, otherwise recycle with concrete and masonry
  • architraves, skirtings, scotia, trim - reuse or recycle if damaged
  • timber panelling - reuse/recycle; if untreated, check regarding paint/varnish finishes
  • specialty timber fittings - reuse (includes mantels, built-in shelving, bookcases, mouldings and window sashes)
  • joinery - reuse/recycle

Timber products from demolition

  • engineered wood panels (EWPs) - reuse
  • native timbers - recycle/reuse lengths greater than 0.6 metres, recycle architectural features that have no borer or other damage, preferably nail-free
  • hardwood timbers - recycle/reuse lengths greater than 0.6 metres, recycle architectural features that have no borer or other damage, preferably nail-free
  • hardwood flooring - reuse if tongue and groove flooring; thin strip flooring is not reusable (too thin for refinishing)
  • laminated beams - reuse
  • timber truss joists - reuse


Storing and handling recyclable and reusable materials

Ensure safe and dry storage of salvaged items and careful removal from the site to reduce damage and contamination that could preclude reuse or devalue the materials.

  • check with clients, salvaged goods dealers and recycling operators regarding any particular specifications for storage and transportation
  • provide and erect barriers and security devices around the site as required to protect the salvaged material from damage, mishandling, theft, vandalism and fire
  • label separated components as they are removed, for easy reinstallation
  • keep all hardware (hinges, screws, rollers, guides, keys) together with the building component such as doors, windows, joinery, HVAC
  • asbestos should only be removed by approved contractors

On-site or off-site waste management?

Decide whether you will separate waste types on site for various recycling, reuse and disposal options or haul mixed waste off site for sorting and separation. You could even have a combination of the two:

  • On-site involves one waste storage area with several skips, bins and piles to keep waste types separate. Several organisations may be involved in collecting the different waste types. Most deconstruction projects involve a large amount of on-site sorting
  • Off-site is the traditional waste management method of having one skip of mixed waste collected by a waste contractor. Recyclable materials are then sorted out of the skips at a designated facility

Key determining factors are:

  • the available space for several bins or piles - where space is limited, off-site sorting is usually best
  • costs - compare recycling service charges and labour for sorting, compared with a waste contractor's off-site service
  • availability of recycling services and waste haulers locally and their ability to pick up materials or whether you will transport your own waste, recyclables and salvaged building items from site
  • availability, training and commitment of the labour force on site
  • whether materials will be reused in the new development
  • whether materials will be directly on-sold from site
  • potential for damage or contamination during transportation off site or during storage on site

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Updated: 13 June 2024