Using MgO boards – important update over permitted use

The potential for systemic failures to occur due to the use of magnesium oxide (MgO) boards have been identified by the LABC Warranty Technical Standards team following research in Denmark. Boards containing either chloride or sulphate-free ions, subjected to high levels of humidity, may leach or “cry” chloride, impacting on fixings, other materials that they come into contact with, and the internal environment within the building.

Following discussions with other warranty providers, building product testers Kiwa BDA, product approval and certification body BBA, and the Magnesium Oxide Building Board Trade Association which represents MgO board manufacturers, we have noted that the impact of this issue in the UK is unknown and that current testing regimes are potentially inappropriate and therefore are proving inconclusive.

Therefore, for warranty inspection and certification purposes, LABC Warranty has agreed with other warranty providers to revise the approach to the use of MgO boards as of today and in all subsequent use cases.

MgO boards that contain either chloride or sulphate-free ions:

  1. Must have full third-party certification from either Kiwa BDA or BBA. They note that the only MgO boards to have this certification currently are the Resistant MgO Board and the Euroform MgO board
  2. Must be used and installed strictly in accordance with the scope of that third-party certification, and importantly only in the locations within the wall build up that are identified in the third-party certificate
  3. Must not be used as an external render board, or as a backing board for direct applied polymer, resin or masonry brick slips, unless they have specific approval for that purpose
  4. May be used as a non-structural sheathing board (subject to items 1 and 2), provided an appropriate breather membrane is used to cover them externally and a suitable vapour control layer has been robustly fitted internally (cladding systems meeting 7.2, 7.3 or 7.7 of the LABC Warranty technical manual will be accepted) Where the sheathing board is being applied to light gauge steel and steel frames a suitable separating layer/membrane must be introduced between the MgO board and the steel element
  5. Must be non-structural, ie they cannot be used as racking boards or structural boards
  6. Can be used internally for non-loadbearing applications, except in locations of high humidity (such as rooms with baths or showers)
  7. Must be fixed with grade A4 stainless steel fixings
  8. Must only use A4 stainless steel fixings for fasteners that penetrate the boards, for example, rainscreen support system bracket fixings

Investigations remain ongoing and we will keep you updated as new information becomes available.

14 March 2019

What are MgO boards?

Magnesium oxide, or magnesia, is a versatile mineral. When used in MgO boards, the boards can be used in walls, fascias, soffits and wall sheathing, thanks to magnesia’s useful attributes such as fire resistance, mildew and mould control and acoustic properties. MgO board is also considered a more environmentally-friendly material than some traditional building materials.

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