Efflorescence: Understanding and Preventing This Common Building Problem

What is Efflorescence?

Efflorescence is a white, powdery substance that often appears on the surface of masonry, concrete, and other building materials. It is caused by the migration of salts from the interior of the material to the surface, where they crystallize and form a visible deposit. Efflorescence is a common problem in many buildings and can be a source of frustration for homeowners, architects, and builders.

Concrete Efflorescence
Concrete Efflorescence (Picture by LIFE)

What are the Causes?

Efflorescence is caused by the presence of soluble salts in building materials such as cement, concrete, and masonry. These salts can be present in the materials themselves, or they can be introduced through water that has seeped into the structure. As the water evaporates, the salts are left behind on the surface and can accumulate over time.

The most common types of salts that cause this issue are sodium carbonate, calcium carbonate, and magnesium carbonate. These salts are highly soluble in water and readily move through the pores in building materials.

Is this a predictable issue?

It is difficult to know for certain if concrete will experience efflorescence, as it can depend on a variety of factors such as the composition of the concrete mix, the surrounding environment, and how the concrete is cured and maintained. 

How can identify the cause of it?

Identifying the source of concrete efflorescence can be a bit tricky, but here are a few steps you can take to help pinpoint the source:

  • Determine the timing: Take note of when the efflorescence first appeared. Was it shortly after the concrete was poured, or did it appear some time later? Was it on the winter or during a rainy season? This can give you a clue as to what might be causing the problem.
  • Look for signs of moisture: Efflorescence is often caused by moisture that has penetrated the concrete. Look for signs of moisture, such as water stains or mold, on the surface of the concrete or nearby structures.
  • Check drainage: Poor drainage is a common cause of efflorescence. Check to see if water is pooling around the concrete, and make sure that any nearby gutters or downspouts are directing water away from the concrete.
  • Check for leaks: Leaks in nearby structures can also cause moisture to penetrate the concrete. Check for leaks in nearby pipes, or other structures.
  • Consider the environment: The surrounding environment can also contribute to efflorescence. For example, if the concrete is located in a humid area, it may be more prone to efflorescence. If the concrete is exposed to salt water, this can also contribute to efflorescence. cold weather and rain, also contribute to efflorescence.

How to Prevent it?

Preventing efflorescence requires controlling the sources of moisture and salts in building materials. The following are some steps that can help prevent efflorescence:

  • Use high-quality building materials: Choose materials that are low in soluble salts and use them according to the manufacturer’s instructions.

  • Properly seal surfaces: Apply a waterproof coating to the surface of masonry and concrete to prevent water from entering and depositing salts.

  • Control moisture levels: Keep the humidity levels in the building low to reduce the amount of water that can seep into the materials.

  • Use proper ventilation (for indoors): Ensure that the building is well ventilated to allow water vapor to escape and prevent the accumulation of moisture.

  • Properly maintain the building: Regular maintenance, including cleaning and sealing, can help prevent efflorescence from forming and spreading.

  • Improve drainage: Ensure that the area around the concrete is properly graded to promote proper drainage away from the surface of the concrete. This can help prevent water from pooling on the surface and causing efflorescence.

  • Use a vapor barrier: Installing a vapor barrier beneath the concrete can help prevent moisture from penetrating the surface and causing efflorescence.

While these measures can help prevent efflorescence, there is always a chance that it can occur. If efflorescence does appear, it is important to take steps to remove it and address the underlying cause to prevent it from recurring.

Removing Efflorescence

If efflorescence has already formed on a building surface, it can be removed by using a mild acidic solution, such as a mixture of water and vinegar. In some cases you can just use a broom to clean it. Sometimes it just goes away with warmer weather.

In conclusion, efflorescence is a common problem in many buildings and on concrete, but it can be prevented and controlled by following proper techniques and maintenance practices. By understanding the causes and taking steps to prevent it, homeowners, architects, and builders can help ensure the longevity and appearance of their buildings and concrete.