The behaviour of water in porous building materials and structures

Abstract

Water is critical to many of the familiar deterioration processes that affect historic buildings, but much of the picture describing how moisture accumulates and distributes itself within materials has been developed in fields outside conservation, and even outside building engineering. In the course of a more-or-less chronological literature review, this paper presents a summary – which is largely nonmathematical – of the current understanding of moisture behaviour in building systems composed primarily of brick, stone and mortar. From considering why porous materials attract moisture in the first place, and the principles behind how transport processes such as wetting and drying are mathematically modelled, the review moves on to look at the additional theory necessary to handle complex building materials and systems. After a short discussion of some building-scale processes such as rising damp, the paper concludes with a summary of some of the issues that remain unresolved.