More and more Modern Methods of Construction (MMC) are being put to use in the construction industry each year. Interest in modern construction methods has extended to the construction of housing as they potentially represent savings in:
- Construction time
- Reduced construction materials
- Higher standards of quality than more traditional methods of construction
The issue with MMC is that, as they are often new constructions methods, regulations have not always kept up with them as well as they should have. What this means is that the rules on how to utilise MMC for a new build can be unclear, which can lead to developers making mistakes. In this Tech Update, we aim to highlight key points on utilising MMC in your developments, as well as giving an overview of the suitability of systems and components.
Key Points to Consider
- Off-site assembly means quicker erection times on-site and weather tight construction achieved much faster
- The accurate setting out of foundations etc. needs to be well managed
- Modern methods of construction, in particular, modular systems and large panel systems, will require advanced planning of the site for access, off-loading, installation and possible storage of systems
- MMC systems have their construction, design and layout planned well in advance so any last minute changes will need to be avoided by utilising good project management from the offset. What is known in the industry as a ‘design freeze’ should be imposed in advance of the production commencing in the factory
- Quality of your end product will largely depend on accurate assembly on-site by factory trained or authorised Specialist Contractors
- Modern methods of construction generally take advantage of standardised construction. This may cause issues when it comes to adapting to complex architectural or design requirements. Additional testing may be required to ensure standards for durability and weather tightness can be achieved. For example, incorporating flat roof drainage outlets through close panel parapet extensions.
Suitability of Systems and Components
When working with Modern Methods of Construction, it is important to ensure that products or systems:
- Meet the requirements of British Standards or equivalent European Standards at the time of application
- Are covered by an independent third-party technical approval body which is accepted by the Warranty provider? This would be either a UKAS accredited or a European equivalent accredited organisation, such as ILAC (International Laboratory Accreditation Co-operation). Details of the testing body accreditation will need to be supplied together with the certification document
- Carry independent third-party testing that recognises UK Building Regulation requirements and additional warranty standards. Details of the performance and the limitations of the use of the material or system must be provided
- Bear (where a corresponding Euro standard exists) a CE marking in accordance with the Construction Products Directive. This shall be supported by evidence of testing carried out on the product
Construction methods which are not able to meet the requirements of our Technical Manual must be approved in advance by LABC Warranty at the design stage. This must happen well before commencement on-site.
Modern Methods of Construction products and systems that have third-party approval will still need to be structurally approved on a site-by-site basis. This will depend on the layout and loading of the component in questions. Thermal properties and measures to prevent condensation will also require specific assessment depending on exposure/orientations.
What kinds of Modern Methods of Construction are there?
MMC construction generally falls into the following categories:
Volumetric or Modular Construction
- Involves the off-site production of three-dimensional units. Quality controlled systems of production in the factory should be in place and expected as part of any third party approval. Modules may be brought to the site in a wide array of different forms ranging from fairly basic structural shells to ones in which all the internal and external finishes and services are already installed.
- Volumetric construction can consist of timber frame, light gauge steel and concrete or composite constructions. External cladding may form part of the prefabricated system, with only localised on site specialist sealing required. Alternatively, traditional masonry cladding may need to be constructed. In this case, specific detailing for the support of cladding, cavity barriers and DPC must be pre-agreed and checked by site managers.
- Panel units are produced off-site in a factory in a quality controlled process and are then assembled on-site to produce a 3D structure. The panels generally consist of wall, floor and roof units and are sometimes referred to as cassettes.
- Involving factory installation of lining materials and insulation. May be constructed of timber, steel frame or concrete panels. Panels often include services, windows, doors and finishes.
Open Panel Systems
- Open panel systems do not include insulation, lining boards or vapour control layers. These are applied to the steel frame on site, together with any external cladding and internal finishing. Therefore, careful control of on-site finishing will be required and the panels must be protected against the elements until weather tight.
- More conventional timber frame panels are typically classed as open panel systems and would normally arrive on-site with the sheathing board fixed but without insulation or internal boards. For warranty purposes, these types of open panel systems can normally be classified as established or traditional construction, providing that such open panel systems have quality assured systems in place and are registered either with the Structural Timber Association or BM TRADA (see Chapter 7 of our Technical Manual (LINK) for general guidance and advice on conventional timber frame construction).
It’s important to note that:
- Bespoke timber frame open panel systems that do not have such QA procedures will need either third-party accreditation or independent structural engineer supervision to be provided to monitor the installation, erection and then completion (sign off) of the system. More information is available in Chapter 7 of our Technical Manual (LINK)
- Structurally Insulated Panels (SIPs) are a form of composite panel. Only systems with independent third-party approval will meet the requirements of the Technical Manual.
The information used in this article is taken from Version 8 of the LABC Warranty technical Manual and is provided as guidance in meeting our technical standards. If working on an LABC Warranty site please check which standards apply.
Please Note: Every care was taken to ensure the information in this article was correct at the time of publication on 2.3.2018. However, for the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty technical manual.