Smarter ways to build homes

By - , Build 135

A BRANZ project is looking at advanced residential construction techniques as a way to use new thinking to solve old problems.

KHK prefab house built for Christchurch’s HIVE project.
KHK prefab house built for Christchurch’s HIVE project.

OVER RECENT YEARS, we have become familiar with often-repeated industry headlines around the sluggish Christchurch rebuild, low productivity, Auckland housing shortage, leaky house crisis and, of course, the affordability issue.

These problems come at a time when the economy is weak, confidence is fluctuating and residential construction is not able to keep up with housing demand, leading to flow-on effects for the economy.

Improvements can be made

To find solutions, the Building Research Levy-funded advanced residential construction techniques project was formed to investigate innovative and advanced construction techniques for the residential construction industry.

Advanced residential construction techniques can improve productivity, quality, profitability and sustainability – economic, environmental and social. They usually involve process improvement and efficiency, as well as the use of more advanced materials or products.

They involve a step-change in materials innovation, products and designs alongside new ways of doing things. The result is a diverse portfolio, including planning, business processes and actual hands-on construction. While the focus is on residential construction, the techniques may come from non-residential backgrounds.

Stage 1 of the project has identified a number of technologies and techniques.

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Joint efforts pay off

In an industry where many companies are small or sole traders, group procurement and cooperatives allow small players to combine to have a big influence.

Pooled capital research and development funds could enable smaller players to undertake and share the risks of their own research and development projects and enable experimentation with materials and processes.

Pooled skills can be distributed to improve operations and workflow across multiple companies. Improved workflow and larger buying power can lead to lower costs and improved competition. With less fragmentation in supply chains, feedback from builder to manufacturer and vice versa is more direct and productive.

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Consistency needed across BCAs

Consistency in the application of the Building Code has been identified as essential for enabling innovative design and construction methods.

Where a home is built in a different building consent authority jurisdiction than its final destination, consistency in the interpretation of the rules is essential to avoid compliance issues. This is particularly important where unusual designs or materials are used. It requires open communication and collaboration between the councils.

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Many benefits of off-site construction

Perhaps the biggest difference between highly productive international residential construction industries and our own is our rigid adherence to traditional on-site construction.

Off-site factory-based construction has the benefits of:

  • a climate-controlled environment
  • reduced on-site work
  • on-site staff
  • quality control
  • enhanced waste minimisation and recycling
  • quality, quantity and custom design team
  • improved health and safety.

Controlled-environment building

Climate-controlled environments allow production in any weather and at any time of the day. Materials are kept dry, preventing timber from twisting or warping or delaying the fixing of internal lining. Schedules are more easily maintained due to the removal of weather-related delays.

More work is done in a predictable environment, workers are based in one place and less time is spent travelling. In addition, employing staff rather than day labourers reduces turnover, and training becomes an investment.

The production line also means that it is possible to have multiple jobs on the line at any one time. Combined with higher materials purchasing, this may enable economies of scale to come into play. The value added off-site relates to the completeness of the house when it leaves the factory. The higher the value at the factory door, the less work needs to be done on site.

Better quality control

Off-site construction enhances quality control. Early identification of issues means rework is kept to a minimum, reducing material and time waste. Tighter waste control also promotes recycling, lowering material and waste cartage costs.

Making it a team effort

Interaction between design, estimation and execution in the off-site context is more like a multi-disciplined team than a set of contractors. Each role is responsible for working with the others to maximise output while minimising inputs – time, materials and energy.

Time and money saved

Greater efficiency of structure at the planning stage reduces the amount of materials needed, amount of work and energy required in construction and, if lighter, lowers the amount of transport energy required to deliver the house to site.

The predictability and designed nature of a factory environment also provides opportunities to improve health and safety, with hazards controlled or eliminated.

Overseas, it has been found that prefabrication improves value for money and can be more cost-effective than traditional construction.

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Automation – the next big step

A step beyond factory-based construction is the use of automation in construction. By employing machinery to do the heavy, menial tasks, workers are able to concentrate on value-added work, expanding the capacity of the business, with more houses built using fewer hands.

The use of automation is a key area when it comes to quality improvement. Computer numerical cutting (CNC) machines precision cut pieces according to CAD geometry, which can be imported from the plans.

This removes the human error factor, significantly reducing waste and rework, and materials procurement can be planned with minimal contingency.

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Where will the findings lead?

Ensuring long-term markets of a workable scale will be the biggest barrier to the widespread uptake of off-site construction and automation by New Zealand’s residential construction industry.

However, with high structural standards and a national marketing campaign based on being ‘green’, there may be significant potential to break into offshore markets by offering a superior product.

The costs and benefits of prefabrication and automation in the New Zealand context will be investigated in stage 2 of the project, which is scheduled for completion in 2014.

Table 1
TYPES OF PREFABRICATION
 
Panellised – open Clad on one side only – usually the exterior.
Panellised – closed Complete panels – electrics, plumbing and insulation installed, walls clad on both sides.
Modular 3D modules consisting of one or more rooms, usually fully plumbed, wired, insulated, clad inside and out.
Hybrid Combination of construction type including modular and panellised.
Transportable Complete house, usually awaiting final plastering and decoration.

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For more

For more The study report with stage 1 results will be available shortly from the BRANZ Shop at www.branz.co.nz.

Download the PDF

Articles are correct at the time of publication but may have since become outdated.

KHK prefab house built for Christchurch’s HIVE project.

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