Update position on the acceptability of MgO boards
The following is an update position on the acceptability of MgO boards for use in conjunction with LABC Warranty projects.
For new projects requiring LABC Warranty 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 LABC Warranty 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.
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 LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty technical manual.