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Masonry And Moisture—What is the Worst That Could Happen?

Moisture has been the number one cause of structural deterioration for as long as there have been structures. Moisture in all its forms—snow and ice, wind-driven rain, water vapor— greatly affect the performance of building materials.

The design of masonry systems should prevent the intrusion of the elements, rain, snow, heat, and cold, into the building’s interior, and it should safeguard the building’s structural components. Any structural break in the wall could compromise your building envelope. Porous or poor quality masonry units are among the most common failure points, such as:

  • mortar joints
  • hairline or shrinkage cracks
  • parapet
  • door and window details

Water can also enter through vapor condensation and can penetrate the structure as a result of poor workmanship, with lack of proper drainage aggravating the impact of any type of moisture intrusion. Vapor condensation can also result from interior sources when thermal properties are not in alignment. The results can take a serious toll on a building.

Structural Problems

With unwanted moisture intrusion, masonry units and mortar can crack. When water enters brick, concrete, or natural stone, thermal expansion can cause the surface to peel, pop out, or flake off. This phenomenon, commonly known as spalling, is caused by excess moisture in the masonry that exerts pressure outward. Eventually, spalling can cause large sections of the masonry to crumble and fall off, potentially leading to structural damage.

Excessive moisture also results in wall rot, an extremely unsightly and unhealthy condition. It can also lead to disintegration of insulation and the staining of interior finishes. Other adverse impacts include deterioration and/or corrosion of the wood/steel backup studs, cladding, ties and reinforcements. If left untreated, the water intrusion can increase and even spread, causing additional structural degradation or, in extreme cases, outright structural failure.

Aesthetic Degradation

High on the list of aesthetic impacts of too much moisture is efflorescence, a white, powdery, crystalline deposit on surfaces of masonry, stucco, or concrete. Essentially, efflorescence is the result of a salt within the masonry unit itself that has been dissolved by excess moisture and has migrated to the surface of a porous material, where it forms that unmistakable white bloom as the water evaporates.

Three problems must exist in order for efflorescence to occur:

  1. There must be water-soluble salts present somewhere in the wall
  2. There must be sufficient moisture in the wall to render the salts into a soluble solution
  3. There must be a path for the soluble salts to migrate through to the surface where the moisture can evaporate, thus depositing the salts which then crystallize and cause efflorescence

Even though sulfates may be present in a masonry wall, they must be dissolved by water in order to result in efflorescence. No moisture means no migration of sulfates to the surface. Certain conditions, however, will aggravate the potential for efflorescence. If the block has been exposed to cold, rainy weather during storage, for example, or to prolonged or heavy sprinkling, or if the structure has been poorly designed in terms of drainage and moisture control.

Health and Safety

According to the Department of Energy Building America Solutions Center, “Moisture is not often thought of in terms of occupant health and safety. Yet indoor air quality professionals consider moisture to be a ‘pollutant’ that can have a significant impact on the occupants’ health.”

Excess moisture causes the growth of bacteria, which can generate new or worsening odors and harmful gases inside the building envelope. The effects can aggravate existing conditions such as asthma and allergies. In some cases these bacteria can even result in cancer and birth defects.

Airborne moisture is ripe for dust mites and roaches, whose droppings exacerbate allergies. Appearance of these pests necessitate the use of insecticides, which have their own deleterious effects.

Mold is a Growing Concern in the Construction Industry

Though mold has been with us for more than 100,000 years, it is now the source of a growing number of legal battles nationwide. Why has mold recently become such an issue in the built environment? The short answer is the change in building materials.

Design and construction practices can have a profound effect on the potential for mold growth. In fact, continued efforts to reduce initial construction costs have resulted in increased use of lighter and/or organic materials that may provide food for mold.

While the quest for energy efficiency is a worthy goal, it has inadvertently created mold-related problems. Unless properly ventilated, tighter buildings are actually an ideal environment for mold growth, as are the givens of modern life, including wall-to-wall carpeting and air conditioning, which causes condensation. Mold arises in buildings because of the lack of “big picture” design. Changes are introduced in one component material or subsystem without evaluating their impact on other aspects of a building’s overall performance.

Moisture Management is Key

In this post, we have highlighted the potential risks moisture can pose to buildings and their occupants. Moisture management must be a top priority when designing and building. In an upcoming post, we’ll cover what you can do to avoid common mistakes that lead to water intrusion. If you don’t want to wait, you can download our guide to Controlling Moisture in Masonry today.

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