Jarvis MMC
Housing System .

In 2005 the Jarvis board decided to respond to the £60k house competition by investing in the development of a housing system which incorporated modern methods of construction (MMC).

The Group's ambition was to increase productivity and to meet the aspirations of the RSL market, which accounts for 40% of our business.

The Company approached other members of the Jarvis Group in order to create a multidisciplinary team. From the Development Company we took project management and design, and from M&E Services, designers with NHER experience. The Construction Director, who also called in his RSL coordinator, headed the team. The plan was to develop a design manual and a range of standard dwelling types that would combine all the benefits of a fully integrated design solution that included:

• System foundations
• Timber frame panelled system
• Pre-fabricated pods

All construction would be to the highest 'sustainability' criteria and maximise quality. Having examined the UK and European markets we selected two timber frame and one window partner. The outcome was a model of MMC efficiency. The innovative system that was developed comprises a closed panel timber frame structure erected on a pre-cast concrete beam system foundation with bathroom and kitchen pods, which is recognised by the BRE as a hybrid solution.

Foundation System

The foundation system has been designed in collaboration with one of our supply chain partners, PRC Structural Engineers, specifically for housing projects. It is the result of over two years' design and development that has seen refinement of the original concept.

Jarvis MMC Housing System

The system is suitable for most ground conditions in that it embraces insitu pad concrete bases or piling solutions according to the local ground conditions, which combine with standard precast concrete beams. These beams facilitate ventilated floor voids and easy connection of the timber frame wall plates. They are sourced from one of two project partner suppliers who have satisfactory warranties for this type of work.

Jarvis provide the transport for the beams that are placed on the pads or pile caps directly from a lorry mounted crane. Engineers supervise the placing in order to achieve a high final tolerance suitable for the closed timber framed panels that follow.

The combination of standard designs that are tried and tested and collaboration between supplier and Jarvis in delivery and placement add significantly to on site efficiency.

• 40% reduction in excavated material to landfill sites
• 55% increased speed of installation
• Economies of manufacture by standardisation of components
• 50% reduction in trades processes

Timber Frame System

The composite timber frame system is an advanced closed panel solution. The timber frame is manufactured off site. It has fully insulated floor cassettes and wall panels that are delivered to site fully insulated and complete with external doors, windows, service conduits and plasterboard.

The roof is assembled on the ground, felt and battened and lifted in position on completion of the wall panels, thus providing a water proof structure within two days. We have been able to produce standard house and flat designs that have produced the following benefits:

• Standard Panels
• Reduced waste
• Reduced transport costs
• Reduced erection time

All panels are pre-plumbed and conduited.

Pre-fabricated Pods

Pods are provided for both bathrooms and kitchens and are designed so that they can be 'grown'. In the case of bathrooms only two typical layouts are required for the ten dwelling types currently on offer, with no change to the range of components.

Kitchens are also in two layouts. House kitchen pods vary in width by introducing one wider floor unit and one wider wall unit, always in the same location. Final service connections from the pods are made within the downstairs cupboard. Pods contain the core of the plumbing for a dwelling.

Kitchen pods include the ground floor WC, plumbing and tails to all ground floor radiators. Bathroom pods contain the plumbing, heating system and tails to first floor radiators.

Passivent system

We have developed a kitchen and bathroom pod system for all of our properties which:

• reduces onsite construction time
• minimises waste
• improved quality
• incorporates all services
• improved acoustics

Conclusion

Having completed a scheme using this innovative system we have been able to reduce our construction period from 20 weeks to nine weeks and the number of site operations from 23 to 13. This has achieved an overall reduction in build cost of approximately 10%, with further sites currently being monitored.

Based on the development of the Jarvis MMC system we entered the ODPM's Design for Manufacture competition and successfully demonstrated that we could meet the £60,000 challenge, and then progressed to stage 2. Our MMC system was recently featured in a case study within the Construction Process section of the Department of Communities and Local Government's 'Lessons Learnt' publication, as an example of best practice in process management.