Water Chemistry and Building Construction

By Andrew Illein

It’s a widely known fact that having uncontrolled or unwanted water inside a wall is a bad thing. Buildings, for one of their most primitive functions, are designed to provide shelter from nature. When water penetrates the outer skin, also known as the exterior cladding system, of a building and comes into contact with underlying materials, the potential for significant damage is obvious.

Water is known as “the universal solvent” and given enough time, most all things will succumb to the forces and actions exerted by water. Why is water such a threat to buildings? The chemical properties of water are very unique. It is the only substance at earth temperatures that can be found in all three states of matter (solid, liquid, gas); it has a neutral pH balance; its molecules will climb upon themselves (the process of capillary action); it will dissolve more substances than any other liquid; and it is necessary for life on Earth [1].

Water can be very reactive with many other substances. In some circumstances, the chemical makeup of water will work to pull apart bonds between other substances, such as salt or sugar. In other circumstances, water will react and separate into hydrogen and oxygen molecules, such as when in contact with iron. This process contributes to accelerated corrosion of the iron and can happen to other vulnerable metallic items such as fasteners, lintels, and beams [2].

The ability of water to support life is also a concern, particularly with regard to mold and fungal growth. When water saturates wood, such as sheathing or wall framing, the moisture can create an environment that attracts spores from the air to survive and potentially flourish on the wood surfaces. Once the spores begin to grow, they may consume the wood as food which creates a process that leads to deterioration and structural damages [3].

The chemical properties of water drive much of the design and materials used in current building envelope technologies. One simple example is the widely accepted use of aluminum flashing in building construction.  Although pure aluminum severely reacts with water, aluminum and oxygen in the air creates an outer aluminum oxide layer that becomes chemically inert and resists reacting with water. This chemical “shell” on the surface of the aluminum prevents water from reacting with the underlying aluminum resulting in the water being directed away from the building by the flashing [4].

Although the study and impact of chemistry is not often thought of in the construction world, an understanding of the underlying science for why construction problems occur may be helpful in determining solutions and contribute to new building technologies that address issues caused by water.

[1] “Water, the Universal Solvent.” USGS Water Science School. United States Geological Survey, 7 June 2013. Web. 24 Feb. 2014.

[2] Senese, Fred. “How Does Iron Rust?” General Chemistry Online: FAQ: Redox Reactions:. Frostburg State University, 15 Feb. 2010. Web. 24 Feb. 2014.

[3] “How Does Wood Rot?” Paint & Coatings Industry Magazine, 1 Nov. 2002. Web. 24 Feb. 2014.

[4] Shwartz, Mark. “Scientific Discovery: Why Aluminum Doesn’t Rust.” Stanford University, 11 May 2000. Web. 24 Feb. 2014.

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