Properties of magnesium oxide boards used as sheathing in exterior walls

Stefanie Wøhler Nielsen, Carsten Rode, Tommy Bunch-Nielsen, Kurt Kielsgaard Hansen, Wolfgang Kunther, Bent Grelk

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Sheathing boards based on magnesium oxide (MgO) became very popular in the Danish market around the year 2010. However, it was realized a few years later that they condensed humidity from ambient air. The leakage from the boards led to severe problems with corrosion of metallic components and moisture uptake and degradation of wooden members. The boards have been banned from use in the Danish market since 2015, while damage cases valuing around 370 million EUR still need to be reconciled [1]. The binder in MgO board is formed by a chemical reaction between MgO and MgCl2. However, MgSO4 is a possible alternative to MgCl2, and such boards may have smaller moisture uptake, to reduce this issue. This paper gives an account of recent activities to compare properties of MgO boards, based on chlorides or sulphates. The investigations comprise: (1) Analysis of elemental composition and crystalline components, (2) Examination in optical microscope and scanning electron microscope, (3) Determination of moisture retention and water vapour permeability, (4) Analysis of chemical composition of leaked salt water from boards, and (5) Visual observation of decomposition and determination of dry mass change after exposure to high humidity.
Original languageEnglish
Article number02091
JournalMATEC Web of Conferences
Number of pages6
Publication statusPublished - 2019
Event4th Central European Symposium on Building Physics - Prague, Czech Republic
Duration: 2 Sep 20195 Sep 2019
Conference number: 4


Conference4th Central European Symposium on Building Physics
CountryCzech Republic
Internet address

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