Home | InSite | Updated Guidance for Magnesium Oxide Boards (MgO)

Updated Guidance for Magnesium Oxide Boards (MgO)

Updated Guidance for Magnesium Oxide Boards (MgO)

Published 8th April 2020 and Updated 16th April 2020

With effect from 15th April 2020, Premier Guarantee no longer accept the use of all types of Magnesium Oxide board (MgO) on any of our structural warranty schemes.

For any new scheme registered with Premier Guarantee, sites not commenced, or plots where foundations commence after this date, alternative products, which have an appropriate British or European Standard recognition, must be used.

Registered sites which are currently under construction with these boards installed, or are in the process of being installed, should replace these with alternative products where practical to do so. Where it is not practical to do so, or for new plots which are part of an existing block, clients should seek approval from their Risk Management Surveyor in relation to this.

We are aware that there are a wide range of MGO boards manufactured to varying quality standards and that there is a huge difference of opinion throughout the worldwide construction industry as to board acceptability. This includes how they should be viewed and tested. In the absence of a harmonised ISO EN, PAS or British standard, this material is reviewed as greater than normal risk. Our main concern has always been to protect our insurers and the end users or homeowners.

We are continuing to work behind the scenes with members of MOBBTA to gain a BSI PAS standard for Magnesium Oxychloride boards so that there can be trust in the industry for use of certified and tested boards that meet a certain minimum criteria.

We have been asked to consider the date and timescale of the guidance to allow the use of boards that met our previous standards, which were manufactured by Resistant and Euroform and have been awarded third party approval Multipro, Multi-pro XS and Multi rend (BBA 15/5255 PS1) and Versaliner (KIWA BDA BAW 18-085/01/A). Where these are used solely within the scope of the certification and in addition, for warranty purposes, not used as racking boards unless structural calculations are provided to justify adequacy.

Please be assured that we have given the surveyors transitional guidance and will work with suppliers and manufactures to ease in the new requirements.

Please be aware that this update replaces any previous guidance issued in relation to the use of MgO board. Failure to make changes as requested, may mean that we will be unable to continue to provide an offer of warranty cover.


Previous position on the acceptability of MgO boards

The following is our previous position on the acceptability of MgO boards for use in conjunction with Premier Guarantee published in March 2019. For the latest position, please see above.

For new projects requiring Premier Guarantee cover, it is important that any MgO boards used in the proposed construction, must have a current and valid UKAS accredited or European equivalent third party product certification that is acceptable to Premier Guarantee and also comply with the conditions outlined below:

1. The boards must have a full third party certification from either Kiwa BDA or BBA. (Product approval certificates for MgO boards from other UKAS or European accredited third party product approval bodies may be considered acceptable subject to review by our Technical Standards team). And;

2.The boards are used only in the locations within the wall build up that are identified in the third party certificate (see also comments below regarding render board applications) and installed in strict accordance with the scope of that third party product approval certification and our warranty requirements set out in the points below. And;

3. In external framed wall constructions: 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 identified in the third party product approval certificate. And;

4. In external framed wall constructions: Boards may be used as a non-structural sheathing board (subject to items 1 and 2 above), providing an appropriate breather membrane is installed to cover them externally and a suitable vapour control layer (VCL) has been robustly fitted internally. Cladding systems meeting Chapters 7.2, 7.3 or 7.7 of our Technical Manual will be accepted. Please note: Where the non-structural sheathing board is being applied to light gauge steel and steel frames, a suitable separating layer/membrane must also be introduced between the MgO board and the steel element.

5. In external framed wall constructions: MgO boards that have a suitable third party product approval for our Warranty purpose, may be acceptable for structural use on a timber frame building providing the project structural engineer provides structural calculations to prove the racking resistance of the timber frame taking account of the limitations of the stated performance of the board in the product approval certificate and that additional bracing may be necessary.

Please Note:

a) The third party product approval certificate must also confirm the MgO board will have a service life durability equal to the building in which it is installed
b) The provision of a breather membrane and VCL as detailed in Point 4 will be required, and;
c) For light steel frame projects, the project structural engineer must provide the Light steel framing with in-built racking resistance and that any MgO board used will not be contributing to the structural performance. And;
d) a suitable separating layer/membrane must also be introduced between the MgO board and the steel element

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 to supporting frame members with a minimum grade A2 stainless steel fixings. (i.e. Screws or nails). Higher grade A4 may need to be specified in certain situations such as coastal locations due to the aggressive environment.

8. All fixings penetrating the boards (e.g. for rain screen support system bracket fixings) are strictly A2 stainless steel fixings as a minimum.

We will keep you updated as new information becomes available.

Please Note: Every care was taken to ensure the information in this article was correct at the time of publication. Any written guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. However, for the most up to date Premier Guarantee technical guidance please refer to your Risk Management Surveyor and the latest version of our technical manual.