Capillary Action

The tendency of liquids to move into or out of tiny, hairlike passages is referred to as capillary action [1].

Capillaries present in the masonry arise partly from the porous nature of the masonry units – stone or brick, for instance, and partly from mortar. Moisture movements which are associated with drying out, shrinkage and thermal movements in response to weather and climatic changes all play their part in producing more cracks [2].

The measured pore size for bricks and mortar is in the range 0.001 to 0.01mm. It is believed that it is the shrinkage cracks which provide the major pathways for the rising damp i.e. capillary action.

References

[1] Science Terminology Glossary (2002), Spartech Software, http://www.spartechsoftware.com/reeko/Glossary.htm#

[2] Academic Press, Inc (1996) http://www.academicpress.com/inscight/05021997/capilla1.htm