How Does Water Move Through Materials?
When there is fluid escape within a property the water will be absorbed into the various structures that make up the building. All domestic and commercial buildings are built with materials that are hygroscopic meaning that they draw moisture from the environment. Under normal environmental settings the moisture contained in hygroscopic materials will be at equilibrium with the moisture content in the surrounding air.
How is water held in materials?
When water is held as bound water, the moisture is held within the cellular or crystalline structure of the materials. This moisture may be sorbed into the cells or can become chemically or physically bound to the surfaces of the cells. There is a small amount of this moisture that is always present in materials and does not need to be removed as it does not compromise the structure. On this note, moisture plays a critical role in the hydration and strengthening process in concrete for example as well as in wooden structures. The water helps with the stability of these structures and provides added overall strength.
Moisture can also be held as free water, which means that the liquid moisture on surfaces are held in the pores of the material. Free water is excess water that has been otherwise drawn into the materials. The other moisture will become bound water and remain absorbed within the material itself, whereas the free water will remain on the surfaces within the superficial pores of the material. All free water must be removed during the restorative drying process to prevent weakened and compromised building structures.
How does water move through materials?
When there is fluid escape the water will continue to move throughout the property into the materials and structures of the building. But how does water actually move through an area and how does it get absorbed? There are two main ways that water moves through and is absorbed into materials including carpets, upholstery, plasterboard, walls, ceilings, wood and all other materials that make up a structure.
Capillary action refers to the movement of liquids through the highly thin, slender tubes or pores of a material such as wood or carpet. It occurs on a micro level as a result of surface tension and adhesion of water to the pore walls. As a result of the surface tension and adhesion of water to the walls, the water will rise to a point where it balances the downward force of gravity. The more narrow a pore, the higher the water will rise. Capillary action is a quicker means of liquid movement compared to moisture diffusion and the liquid will move faster through the pores and capillaries of materials when there is less surface tension.
Moisture diffusion moves liquids into materials more slowly compared to capillary action. It refers to the movement of water vapor molecules through the mass of the material and is driven by moisture gradients and vapor pressure differences. Despite being a slower process of the movement of water compared to capillary action, it is an essential process by which excess bound water is effectively removed from water-affected structures. For example when remediation of wet structures occurs with the drying process, water diffusion plays a key role in moving the water from within the structure to the surface of the structure instead where it will evaporate.