Modern methods of construction (MMC) are now used across the construction industry, and particularly to build new homes. MMC offer potential savings in time and materials and can provide higher standards of quality than conventional construction methods. Off-site assembly means quicker erection on site and the ability to achieve a weather-tight construction within a shorter period of time.
While off-site construction is generally well managed and auditable, there are a number of additional factors that those using MMC must bear in mind. With traditional building methods, certifiers have developed a good understanding of the associated risks. This is not the case with many new methods, and although the risk of systemic failure is low, the consequences could be severe. Insurers therefore seek to ensure that systems are correctly certified, and that they are manufactured and built in line with that certification.
MMC typically fall into the following categories:
- Volumetric or modular construction involves the off-site production of three-dimensional units. Modules may be brought to site in a variety of forms, ranging from a basic structural shell to complete rooms with internal and external finishes and services already installed.
- Panelised systems involve the off-site production of panel units, which are assembled on site. The panels may consist of wall, floor or roof units, sometimes referred to as cassettes.
Closed panel units may be built of timber, steel frame or concrete panels. Lining materials and insulation are installed in the factory. Panels often include services, windows, doors and finishes.
- Open panel systems do not include elements such as insulation, lining boards or vapor control layers. These are applied to the frame system on site, together with external cladding and internal finishing. Careful control of on-site finishing is therefore required, and the panels must be protected against the elements until weather-tight.
- Site-based structural systems, such as insulated concrete formwork, are not considered to be manufactured off-site. These systems require third-party approval to secure a warranty, and their acceptability relies heavily on the procedures in place to ensure correct installation on site.
With MMC, the construction, design and layout of a typical system is planned in advance and a “design freeze” is imposed before factory production begins.
Testing is often needed to ensure that standards for durability and weather-tightness can be achieved.
To obtain approval by a building certifier, MMC systems must:
- Meet the requirements of relevant local building codes, or international equivalents current at the time of application.
- Be covered by a current approval from an independent third-party technical approval body. Details of the testing body’s accreditation will need to be supplied to the certifier, together with the certification document.
- Have been subject to independent third-party testing that identifies equivalent local test standards have been verified. Details of performance and the limitations of use must be provided.
At CertMark, we operate the CodeMark™ certification scheme, which is recognized by the Australian and New Zealand governments and allows MMC providers to show evidence that their systems are fit for purpose. This scheme removes the requirement for individual site assessments in place of a general certification.
For further information regarding CodeMark certification, please contact our friendly team members on 1800 CertMark (237 862) or email Office@CertMark.org.