Moulds -
many types, commonly Penicillium spp, Aspergillus spp, Cladosporium spp

Habitat:

These feed on free sugars in wood or surface deposits of detritus, and are found on the surface of damp wood, plaster, wallpaper or paint.

Identifying features:

Surface growths are usually downy and produce masses of powdery spores. They are of various colours, depending on the species - black, brown, green, occasionally pink or yellow. Some are rusty red and can be mistaken for spores of Serpula lacrymans. Some may produce a fluffy mass of white growth which can be mistaken for dry rot mycelial growth.