In recent months, the Premier Guarantee Technical Standards team have been conducting in-depth research into the use and performance of MgO boards, following some potential systemic failures in Denmark.


When subjected to high levels of humidity, the boards are prone to leaching chloride, which can have an effect on fixings and the internal environment within the building. The true impact of this issue within the UK is not yet known, however we are aware that these boards are used on a number of our developments.


The Premier Guarantee Technical Standards team have consulted on this issue with the NHBC, Kiwa BDA, BBA and MOBBTA, a trade association for magnesium board manufacturers.


From these meetings we have realised that there are some inconsistencies in the testing of building products and that there are limiting test requirements that confirm that the board will not leach. As a result, it has been agreed that, at present, these boards may only be used where all the following conditions apply:


  1. The boards have full third party certification from either Kiwa BDA or BBA.

  2. The boards are used and installed in strict 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 (see comment re render board below).

  3. The boards shall 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. The boards 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 our 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. The boards are non-structural, i.e. they cannot be used as racking boards or structural boards.

  6. The boards can be used internally for non-loadbearing applications, except in locations of high humidity (such as rooms with baths or showers).

  7. The boards are fixed with grade A4 stainless steel fixings.

  8. All fixings penetrating the boards (e.g. for rainscreen support system bracket fixings) are strictly A4 stainless steel fixings.


At this time, the above applies to MgO boards that contain either Chloride or Sulphate free ions.


BBA and Kiwa BDA have informed us that, at present, the only MgO boards that are available with third party certification are the Resistant MgO Board and the Euroform MgO Board.


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


Please email with any issues, queries or concerns you may have with the above information.