Its position within a wall build-up determines whether a construction is safe or damp-prone. Note that mould does not require the dew point to be reached: growth becomes likely at sustained surface humidity around 80 per cent, at a surface temperature warmer than the dew point. This is why a wall can grow mould while looking and feeling dry.
Related terms
Seeing this in your building?
The free diagnostic works out the mechanism from what you can see and measure, and tells you what it cannot conclude.