In recent years the UK building envelope industry has witnessed the introduction of magnesium oxide (MgO) boards into the cladding sector, most typically as the sheathing board on SFS backing walls. MgO has been favoured because it is non-combustible (typically class A1 to EN 13501-1), relatively lightweight and easy to cut.
However, there are a number of manufacturing processes by which MgO boards can be manufactured, one of which involves the use of magnesium chloride. In high humidity conditions this can suffer from sweating/leaching releasing chloride which can cause corrosion of metal components, particularly fixings, in contact with the board. There have also been reports of timber in contact with the board being adversely affected.
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