Dampness or moisture within masonry is the other area of observation the specialist surveyor must understand. A knowledge of general construction, basic design, materials and methods is essential. In underground structures and enviroments that knowledge must also extend to soil and rock strata, water tables and salt content. A knowledge of topography and drainage is essential.
The effects of moisture within structures include germination of fungal spores, timber is often in contact with masonry and thus provides habitats for insect colonisation typically wood boring insects, and the effects of capillary action rising from the ground through porous materials and migration of ground salts in solution.
Moisture from external sources such as rain and high ground levels will also enter a building unless design and materials prevent that.
Climatic extremes also cause moisture to enter buildings via flooding.
The specialist surveyor therefore must be knowledgeable. However he is also often the specifier and manager of remedial works. Thus he needs a working knowledge of procedures, health and safety, materials and installation. 
The main categories of moisture ingress in masonry are -
- Absorption by the building fabric of dampness from Internal atmospheric moisture from water vapour and condensation. Atmospheric moisture is dealt with elsewhere in Internal Enviroment and toxic mould.
- Penetrating damp from gutters, downpipes, high ground, cracks, open mortar joints.
- Lateral dampness from high ground levels including basements and cellars.
- Rising dampness due to lack of or defective damp proof course.