11.1 MMC Systems

11.1.5 Site management (handling, storage, and protection)

Materials, products, and systems shall be handled, stored, and protected in a satisfactory manner to prevent damage, distortion, weathering, and degradation. Issues to be taken into account include:

  1. storage
  2. temporary weather protection
  3. protection from damage during storage, transportation, and installation.

MMC systems should be:

  • transported, lifted, handled, and stored in accordance with the manufacturer's recommendations, site installation manual and temporary weather protection method statement
  • stored off the ground
  • delivered in a sequence to avoid or minimise storage
  • suitably protected against condensation, weathering and mechanical damage during storage, transport, and installation.

11.1.5.1 Storage

The storage of MMC systems should ensure:

  • units are stored in accordance with the manufacturer's recommendations
  • storage areas are clean and dry, level, and free from contaminants
  • units are arranged and protected to prevent accumulation of trapped water
  • units are arranged in sequence for erection, with markings visible and adequate access for lifting gear
  • storage areas are suitably located, or protection provided to avoid staining and accidental damage by site traffic.

Packers or bearers placed under units should be located under stud positions or suitable bearing points in accordance with the manufacturer's recommendations.

Stacking

Where units are stacked on top of each other during storage, the storage area and bearing points should meet the required tolerances defined in the System Manual for foundations and be suitable packed and levelled to ensure no deformation of the structure. The System Manual should define:

  • the maximum stacking height of units (ie the number of units that can be stacked on top of each other)
  • method of temporary unit connections (for volumetric units) to ensure effective load transfer and resistance to sliding.

11.1.5.2 Temporary weather protection

The System Manual should include a moisture management plan to outline the design, method and controls for protecting the units from weather exposure and damage during storage, transport and installation. The plan should consider:

  • details of any temporary openings that may be required in the protection layers (eg for lifting or installation/connection of units)
  • continuity of temporary weather protection post installation
  • method of sealing between units and around lifting/connection points
  • method and timing for removal of temporary weather protection materials (materials left in situ post installation should be assessed for condensation risk in the permanent design).

To minimise the effect of condensation or moisture trapped within the unit, consideration should be given to:

  • choice of materials used as temporary weather protection (ie, vapour resistivity of membranes)
  • periodic condition inspections
  • use of desiccant products
  • storage time limits
  • providing drainage points to allow trapped water to escape.

The System Manual should include details about any relevant exposure time limits. Exposure time limits should consider:

  • maximum duration for external storage, and
  • maximum duration of exposure following installation until permanent claddings are installed.

The performance of gypsum plasterboard linings can be significantly affected by wetting. Factory installed gypsum linings showing signs of facing paper delamination or mould growth due to construction moisture during the storage, transport or installation phase should be removed and replaced in accordance with plasterboard manufacturers recommendations, and the supporting structure checked.

Closed panel systems

Where timber and light steel framed walls incorporate linings or opaque membranes to both internal and external faces there is a risk of moisture being trapped within the frame void during the storage or construction phase. Consideration should be given to providing means of drainage to the base of panels to allow trapped moisture to escape.

Volumetric systems

The tops of volumetric units should be designed with adequate falls to avoid the risk of standing water. Water should be directed away from unit joints and cavities. Suitable provision should be made to provide temporary drainage to discharge to rainwater outlets or be designed to shed water clear from the building façade.

Materials used for sealing between units or around lifting points and temporary openings should be suitable for use in cold and wet conditions and UV resistant suitable for the exposure period.

Floors

Consideration should be given to the location of water-resistant membranes in floors (eg to the undersides of floors), and care should be taken to avoid the risk of trapped moisture within the floor structure.

Timber

Moisture content readings of structural timber to closed systems (including: closed panel timber frame, volumetric systems formed entirely of timber or volumetric systems incorporating timber frame backing walls and floors) should be undertaken as part of system verification activities, further guidance can be found in Clause 11.1.10.

SIPs

Panel edge protection should be provided at the base of SIP panels susceptible to moisture damage to prevent wicking of moisture from the floor during construction. If a panel becomes saturated during construction, specialist advice should be sought.

11.1.5.3 Protection from damage

Panel edge protection should be provided at the base of SIP panels susceptible to moisture damage to prevent wicking of moisture from the floor during construction. If a panel becomes saturated during construction, specialist advice should be sought.

To minimise risk of damage from handling of units, consideration should be given to the following:

  • handling of units should be planned and reduced to a minimum
  • packing should be used to ensure that scaffolding does not damage units during installation where panels incorporate factory installed external finishes
  • protection to permanently exposed surfaces, especially arrises and decorative features with timber strips, hessian, or polyethylene.

Practical steps should be taken to avoid the risk of damage and staining to units and finishes during construction.

Internal finishes and fitments

Appropriate protection should be provided to all internal finishes and factory installed fitments (including to doors, trim, balustrades, panelling, and other special features) to ensure they are not damaged. Factory installed sanitary ware and kitchens, including cupboards, doors, fittings, and worktops, should be suitably protected.

Last updated: 2nd January 2025

Back to top ⇧