The Egan report highlighted the need for off-site manufacture to increase the quality of the end product and to reduce programme times.
Zurich Insurance Building Guarantee has always considered it vital to take an open-minded and supportive view of new techniques and innovation. Its technical manual, Solid Foundation, gives guidance for innovative designs and construction methods, and the company has reviewed many systems using such materials as timber, light gauge steel and masonry and found them to be entirely acceptable for warranty purposes. What problems there are are not insurmountable. Many of these problems do not solely relate to factory-produced systems, but are also applicable to traditional forms of construction.

  • This article is a summary and not necessarily a comprehensive review of the subject matter. The views expressed in this article are those of the author only and not necessarily those of Zurich Insurance Company.

    Q - How do you stop a lack of interface between the factory-made component or system and the site-produced element of construction?

    A- Causes
  • Shortage of information
  • Insufficient training

    It is not uncommon for site-produced substructures to be under- or oversized, or to be outside the allowable tolerances, in relation to the factory-produced superstructure. Structural openings formed to contain factory-produced elements can also suffer inadequate “sizing”. Ensure that drawings and details for both site and factory are compatible. This is of particular concern with regards to dimensions and associated tolerances. The training of personnel, including adequate supervision, is still a requirement for a successful project. Dissemination of information from designers and manufacturers to site level is a must. The “we can get round that” approach, often adopted on site, is not a viable option when installing factory components.

    Q - How can you prevent factory components being damaged en route to, or on, the site?

    A - Causes
  • Poor protection or transportation methods

    Ensure that transportation methods are suitable for the intended destination. This is of particular relevance to inner-city developments where restriction on load sizes must be adhered to. Off-loading access points should, where possible, be close to their final destination. Lifting from the transportation mode direct to final position is preferable, avoiding double handling. Appropriate lifting points are required and must be used when moving heavy components. This will avoid damage through racking or dropping the item. Lifting of heavy, large components using appropriate plant and machinery should only be carried out by suitably trained operatives. This is a requirement of the Health and Safety Executive. Components and systems that are prone to deterioration through the effects of moisture must be protected from inclement weather during transportation. Once the item or system is installed, then protection may still be required until the building envelope is complete. Components or completed modules should also be protected from general site traffic. In particular, completed modules should remain sealed until as close as possible to completion date.

    Q - How can you prevent on site alterations being made to factory-produced systems or components?

    A - Causes
  • Insufficient lead-in time
  • Factory production incomplete

    Clients must be aware that once production has been agreed, then the installation of “extras” is difficult to incorporate during factory production. On-site alterations are not advised. Ensure that a full client brief is provided to the designers and agreed before handover for production. One of the main advantages of factory production methods is the perceived increase in quality. It is essential that the full benefits of off-site manufacture are realised by ensuring that components are complete before they leave the factory gate.

    Q - How can you avoid inappropriate claddings and associated detailing?

    A - Causes
  • Lack of detailing
  • Under-specified cladding
  • Cavity barriers missing or incorrectly installed
  • Movement joints inadequate or omitted

    Location of the building with regards to exposure is essential. Use of rainscreen claddings and associated cavities is vital to prevent water penetration. They should be correctly detailed, especially where openings and service entries penetrate them. Lapping of membranes needs also to be addressed, along with continuity with other items. The installation of claddings needs to be compatible with the rest of the superstructure. Fixing points are of particular concern. Demarcation of appropriate places is essential to ensure longevity of connections for the outer surfaces. Cavity barriers must be installed and positioned to prevent spread of fire. Bear in mind movement of various materials, particularly when there is an interface between those of differing properties. Also consider expansion and contraction, both in the vertical and in the horizontal plains. Correct detailing of the joint is not only vital to allow for expected movements but also to prevent moisture penetration. Sealants should be used to form a robust long-term solution.