Damp can occur anywhere and any place in the world. However, the main reason for the dampness is the lack of insulation in walls, floors and roofs. Warm air (i.e. air with high humidity) contains lots of water vapour. If this warm air strikes an external wall that is cold because it is poorly insulated, the water vapour changes to liquid water as soon as it strikes the cold surface. This moisture appears on the wall’s surface and over time mould spores grow.