Designing for Waste Minimisation
While C&D waste is actually created by contractors on site, the decisions made by designers have a major influence on the type and amount of waste. Deciding what and how to build, whether to demolish or renovate, what materials to use and the design specifications for construction all impact on the waste created during the project.
At this early stage the design team have an opportunity to ensure waste reduction is an integral part of the project by:
- gaining client commitment
- influencing the client brief
- taking a team approach to the design and building process
- establishing waste minimisation goals
- researching and gathering information
- carefully considering site development.
These principles should then carry through to the:
Use the initial consultation with the client to discuss incorporating waste minimisation in the project. Ways to help gain client commitment:
- Highlight the environmental impacts of construction and the triple bottom line (environmental, financial and social) benefits of reducing these impacts by minimising waste.
- Present case studies of success in other similar projects.
- Collate information to show potential financial savings and benefits.
- Suggest they talk to previous clients about their experiences with minimising waste during construction.
- Explain the importance of spending sufficient time on design. A detailed brief and comprehensive design detailing will minimise waste through the construction of buildings that meet the client's needs and by eliminating or substantially reducing the potential for unnecessary variation.
- Explain the potential for lower whole life costs relating to their building. Using materials that are more durable, for example, will reduce waste and costs associated with repairs and maintenance.
The initial consultation also provides an opportunity to influence the client brief. This can reduce waste by potentially avoiding full-scale demolition and over-design, by using materials that reduce waste and by incorporating features that reduce waste during the lifecycle of the building.
Issues to discuss:
- Repair and refurbishment in preference to demolition and reconstruction or specify deconstruction to recover a high proportion of materials.
- Use of salvaged building materials.
- Use of materials that last longer and require less maintenance
- Including space for waste sorting and storage during occupancy.
- Building smaller buildings that are better designed for your client's needs.
- Designing the building to be flexible for future uses.
A team approach by the owner, builder, designer and others involved in the building process is the most effective way to implement waste reduction. A team that communicates well from the beginning of the project will help in the identification of ways to reduce waste and is also likely to reduce delays and cost over-runs.
When building a team it is important to:
- seek out other design professionals who express an interest in waste minimisation
- include the main contractor and key subcontractors in the design team if possible or include a team member with expertise in construction methods and planning
- if possible include suppliers in the team - their involvement can help ensure specified materials save unnecessary waste, cost and labour during construction
- establish roles and responsibilities for minimising waste
- encourage ongoing communication about waste minimisation, for example, by establishing waste minimisation issues as a regular item on the agenda for design progress meetings
- educate the team about the impact of construction on the environment
- ensure the team understands the opportunities for improvement.
- Explore goals and objectives that reduce waste/waste streams at different stages of the building's life, from design through post-occupancy. Goals and objectives should be as specific as possible.
- Obtain agreement and commitment from the entire design team on waste goals and objectives.
- If using second-hand materials, find out what is available - contact salvage dealers, and your city or district council for the nearest material exchange premises.
- Use the REBRI Resource Routing Calculator to review the impact of using salvaged material on project costs.
- Research new building practices and materials that reduce wastage.
- Ensure that you keep up to date on product information and changes in materials standards. Keep your libraries of manufacturers' product literature and specifications current and attend trade information briefing sessions presented by manufacturers and industry associations. Reading building trades publications promoting resource efficient building is also recommended.
- Develop a preferred specification list that includes materials and components that use recycled or reused constituents, and utilise recyclable or reusable packaging.
- Develop a set of standard details for use on projects.
- Identify local infrastructure for recycling of construction and demolition waste - contact your city or district council for further information.
The importance of a thorough site investigation can never be underestimated. Awareness of existing site conditions reduces waste by preventing design variations and over-specification that result in unnecessary and additional landfill waste. There are additional factors to consider if there are existing buildings on the site.
Clear ‘greenfield' site
- Design to reduce removal of vegetation (which often then becomes solid waste) and soil.
- Protect specimen trees and areas of special ecological significance.
- Identify composting opportunities and indicate the potential volumes and types of materials generated by the project.
- Maintain the integrity of the site by designing to minimise cut and fill.
- Design according to the contours of the land to ensure minimal impact upon soil excavation. For example, sloping sites may lend themselves to split level design while level sites are appropriate for slab floors.
- Ensure topsoil is retained and replaced after construction so that existing nutrients can be returned back to the site. This will reduce the need for transporting excess soil away from the site and disposing of this valuable resource.
Redevelopment ‘brownfield' site
- Factor in waste generation and costs when advising clients as to most appropriate options - alterations and additions, demolition and deconstruction.
- If renovating, consider reusing buildings and components.
- Consider deconstruction rather than demolition.
- If deconstructing and/or demolishing, identify reuse and recycling opportunities and indicate the potential volumes and types of materials generated by the project.
- Maximise the use of reclaimed materials from the old building(s) in the new building(s). Second-hand building parts can be used for structural, functional or decorative purposes in new buildings. Parts of buildings can be reused, or entire buildings can be relocated and re-erected.
- Consider reusing existing buildings - renovating a structurally sound building is usually more material efficient than starting from scratch.
- Relocating a building requires the same design checks as building a new building - check the Building Code and Building Act 2004, as the relocated building must comply with all new standards and codes regardless of whether it complied with standards at the time it was first designed, recalculate all relevant load bearings, design foundations and civil works to suit the building and check the consent requirements for the Resource Management Act 1991 and make sure the building complies in the new location.
To minimise waste when defining the building type, function, core materials and core design, consider the following:
- Plan for end use and deconstruction so that, when future modifications or decommissioning occurs, the entire structure can be taken apart and reused or recycled with ease and minimal waste.
- Check the design concept matches the actual needs required from the building owner or occupier to avoid over-design and use of excess materials.
- Keep the design simple so that it will be easier to build and hence less likely to have things go wrong during construction. Simple designs also tend to require less maintenance.
- Design the building so that it can be easily adapted for other uses over time. Consider how the building will be used in 10, 20 or even 30 years time. Ensure spaces are flexible (to allow for changes in usage) and future-proofed against advances in technology and trends.
- Select materials that reduce waste and that have recycled content. Factors to consider include durability and reuse and recycling options (see Building material and product selection). Use materials that are consistent with the expected life of the building.
- Dimension to suit standard modular construction sizes - so that the floor, ceiling and wall surfaces conform to the size of sheet materials, which will reduce unusable off-cuts and make the most efficient use of materials.
- Investigate reusing existing buildings and materials to reduce demand for resources, lower waste volumes and save money. Renovating a structurally sound building is usually more material efficient than starting from scratch.
- Use prefabricated and precut components where ever possible. Off-site fabrication can reduce waste, facilitate separation of waste streams and improve recovery rates. Resource use is generally more efficient at the manufacturing site.
- Plan the building to reduce vegetation clearing and earthworks. Consider piles and suspended concrete, timber or metal floors especially on sloping sites, to avoid excess excavations for slab floors. Reducing disturbances to the land reduces waste, reduces the ecological damage and reduces resource use.
- Consider design to minimise temporary works - early consultation with constructors can provide valuable insights into alternative methods and materials to achieve this.
- Less is more - design for simplicity, making construction easier, and avoiding the likelihood of rework. Use fewer finishes and find low technology solutions if possible.
When developing and finalising the design, prescribe building techniques that reduce maintenance, fixing or replacing of components and consider the following issues:
Coordination of the services content of a project is important, as services account for around 30% of the total building cost, and will lead to more efficient use of materials and generate less waste.
- Obtain a good understanding, and where possible, discuss with relevant trade subcontractors and consultants the potential to design in more efficient distribution routes for building services. A simple example is ascertaining whether various service runs can go into the one trench, which has a favourable impact upon waste minimisation.
- Reduce pipework lengths and gully traps and so on by grouping wet areas, such as kitchens, laundries and bathrooms, close together and placing the hot water cylinder centrally in this group.
Footings and slabs
- For precast concrete slabs, bend reinforcing around the corners to minimise overlap, or use straight bars with off-cuts bent and overlapped at corners. Ensure that steel use is compliant with the requirements for reinforcing of concrete such as in NZS4203.
- Use crushed concrete or crush suitable waste materials on site (concrete crushing operators should be familiar with specifications for concrete that incorporates waste material).
- Break up concrete off-cuts or waste concrete and incorporate into hard stand or hardfill.
- Ensure that the structure's dimensions suit the precise sizing of the masonry units.
- To maintain standard brick courses, consider modifying the width of any wall cavity to suit the unit sizes.
- Design for standard product dimensions.
- For steelwork, ensure that spans and bays are dimensioned to the full working length in order to maximise the value of steel members.
- Use prefabricated and precut components such as wall framing and roof trusses.
Roof and wall cladding
- When determining eave widths, check the standard sheet sizes for linings and design accordingly. If eaves are not horizontal, allow for angling in sizing.
- Where the design involves a concrete tilt up slab construction, check the standard reinforcement steel fabric length. The panels should be designed to suit the fabric dimensions. Where possible, span the panels horizontally instead of vertically, which reduces requirements for excavation and concrete.
Glass and glazing framing
- Design custom glazing panels to use multiple replicates of the same size units wherever possible.
- If a wider than normal staircase is required, before determining the actual width, consult a professional staircase manufacturer who will be able to advise you on the most economical widths in relation to length and size of standard materials that are required and available for your design.
- Before designing balustrades, consider the materials to be used and, once these have been established, investigate the standard sizes available in order to minimise waste.
Linings and finishes
- Design passage and doorways to suit architrave and door sizes.
- Design ceiling heights to conform with plasterboard sheet sizes and a combination of cornice and skirting sizes.
- Consider designing bathroom dimensions to suit floor and wall tile sizes, or standard vanity, shower or bath sizes.
- Where a suspended ceiling is used, run the non-structural walls to the ceiling, rather than the ceiling between the walls, to create a continuous ceiling grid. This allows flexibility to move partition walls without causing damage to the ceiling.
Space for operational recycling
Design to reduce waste during the occupancy of the building and incorporate adequate space for segregation and storage of recyclables, organics and so on.
- Obtain information from the client on the projected waste streams including type and quantity of recyclable materials generated by building users.
- Incorporate bins into the kitchen/cafeteria and design for separating organic, recyclable and non-recyclable items.
- Position compost bins, organics collection bins, or worm farm areas so that they are easily accessible from the kitchen/cafeteria.
- Co-locate or incorporate loading, storage and pick up areas appropriately for both industrial and domestic quantities of waste for recycling.
Design for flexibility
Over a building's life, it may change ownership several times and be used for many different purposes. The original design dictates how easy it is to retrofit the building, and how much waste is created during each renovation. Some detailed design considerations:
- Maximise the distance between load-bearing components or design the load-bearing components to the edge of the building to allow flexibility with the internal arrangement of partitions or temporary walls.
- Use modular design techniques so that adding on to, or altering, the building is easier in future.
- Design for a greater load on the foundations and lower storey supports to allow for upper stories to be added in future.
- Allow good access to wall and ceiling spaces to allow for service upgrades and modifications.
- Allow flexibility with lighting, heating and ventilation wiring and controls for changing building uses.
Design for deconstruction
The largest contribution to the landfill and cleanfill will be when the building reaches the end of its useful life. Designing for deconstruction means considering the durability or recyclability of building components and the ability for components to be separated during deconstruction for recycling or reuse. Simple things can make a big difference to wastage in the demolition phase:
- Design entrances wide enough for deconstruction machinery to reach the inner building and upper floors.
- Specify fixing mechanisms that can be reversed without causing damage, e.g. screws, clips, bolts, and gaskets in preference to rivets, mastics, adhesives and tapes.
- Use components and equipment that have a long life and are easily maintained so that they can be reconditioned for reuse.
- Specify materials that can be easily recycled.
- Use reversible construction and assembly sequences.
See the Scottish Ecological Design Association (www.seda.uk.net/index.php?id=136) for detailed information about designing for deconstruction.
Building materials are often selected based on lowest cost, aesthetics and short-term needs. However, to identify the most effective materials to use in order to reduce waste, it is important to use a broader set of criteria when choosing materials such as:
- recyclability - can the product or material be easily reprocessed back into a useful product or material
- resource efficiency - less materials have been used to produce the same product
- future salvage and reuse - whether there is a useful life for the product/material following its original use
- durability - how quickly a product or material will need to be replaced - the more durable, the less wasteful.
Product suppliers can tell you this sort of information, or check the information on product labels.
Specify materials that achieve waste reduction, including:
- materials and components that are reusable or can be recycled after their useful life in the building
- materials with known recycled content - this reduces the use of raw materials and helps boost the market for recyclables
- second-hand or salvaged materials
- materials where durability is consistent with the building's anticipated life - reducing the frequency of replacement
- materials that don't need finishes, e.g. natural timber ceilings, bricks and tiles, pigmented concrete or plaster, or colour-coated long-run roofing steel, which reduces waste associated with finishing products
- prefabricated materials supplied to the specifications of your project - which means no resizing on site
- materials that have recyclable or reusable packaging.
Avoid over specifying - e.g. specifying 9 mm plasterboard when 6 mm is appropriate - this reduces the amount of materials going into a building. Consider whether lower standards or performance specifications may be appropriate if waste can be reduced as a result.
- Prepare accurate drawings - clear, comprehensive, accurate documentation will reduce the likelihood of design variations.
- Provide detailed drawings and instructions to contractors to minimise mistakes, rework and temporary works.
- Document your design, including the location of all services, keeping records of the as-built design, and leave it with the building's owners or occupiers. This will ensure that alterations, maintenance and deconstruction are easier and less wasteful.
- Provide 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.