Much-acclaimed modern pre-fabrication techniques are fine for greenfield sites but are not flexible enough for use on many brownfield sites, a trial has confirmed.

Manufacturers of modern methods of construction (MMC) must explore ways of becoming more flexible and adapting their product to suit brownfield sites, reports Linden Homes, who has just completed the trial.

The brownfield developer found that despite the many advantages of MMC such as reduced on-site waste and greatly improved speed of build, the uniformity of MMC meant that it was more suited to greenfield land than more irregular brownfield sites.

Linden undertook the trial as part of its ongoing commitment to finding new innovative ways of house building that will enable the industry to respond to the increasing demand for new homes, quickly and effectively.

It believes the potential of MMC is vast and will be continuing to monitor the four homes for energy-efficiency and movement over the next twelve months. However the industry is not yet well geared to deal with MMC and increased investment from manufacturers is required to reduce costs.

Trial results: Advantages

• Reduced wastage resulting in more environmentally friendly construction
• Reduced labour on site and reduced dependency on trades such as electricians and carpenters
• Improved speed of construction. The first home was up and in the dry within 5 days, compared to 2 – 3 weeks for a traditional timber-framed home
• High standards of engineering. The homes fitted together well once they arrived on site
• Increased energy-efficiency with improved insulation

Trial results: Disadvantages

• Inflexibility. Pre-made units do not fit easily into irregular brownfield sites
• High costs. MMC is still expensive and it can be difficult to achieve the necessary economy of scale

Linden Homes is well versed in the use of conventional, open-panel timber frame, so a closed-panel timber frame solution was a natural progression.

Linden selected Pace Timber’s Optima system, which it felt was sufficiently advanced to be relatively problem-free, whilst not so far advanced that Linden could not influence the outcome. The next step will be to develop modular bathrooms and en suites that arrive on site assembled.

From an environmental perspective, Linden found MMC produced considerably less waste and resulted in more energy-efficient homes, due to excellent thermal insulation and a tighter engineered solution with reduced air leakage.

Philip Davies, Chief Executive of Linden Homes commented: "We are pleased with the outcome of the MMC trial in Woking, and remain committed to exploring ways of developing the concept on future developments."

"One way of doing this may be to build up from the work currently being undertaken by timber frame manufacturers, increasing the amount of work carried out by them at factory level such as pre-fitting Velux windows in the roof. The industry is already well equipped to deal with timber-frame house building and advancements in this process."

"Ultimately cost is the biggest hurdle which needs to be overcome if we are to take the leap of faith into MMC on a major scale. Considerable investment is needed from the manufacturers to streamline the process more, but I do expect costs to come down as the product develops."