by | Jan 23, 2017 | Uncategorized


Building Envelope Ottawa Reserve Fund Planning ON


You’ve seen it on a lot of buildings, perhaps even at your Condominium Corporation.

That white powdery substance is called efflorescence, it’s a deposit of soluble salts which is most obvious during the winter but may also be observed throughout the year following heavy rains and sudden drops in temperature.

Often, it is apparent just after the structure is completed when the designers, builders, and owners are most concerned with the appearance of the new structure.

The Causes

Efflorescence is caused by a combination of three factors.

First, there must be a soluble salt in the masonry. Second, there must be moisture present to dissolve and transport the salt to the surface. Third, there must be some force such as evaporation to move the solution. If any one of these factors is absent, efflorescence will not occur.

Sources of Salts

There are many sources of salt, including clay bricks, concrete blocks, mortar, admixtures, and groundwater. Efflorescence-producing salts are usually sulfates, carbonates, sodium bicarbonate, or silicate. However, almost any soluble salt, such as chlorides, nitrates, and others, may appear as efflorescence. Since chloride salts are highly soluble in water, rain will often wash them off the surface of the masonry wall.

On occasion, there is also something called “green stain”, the result of certain vanadium and molybdenum compounds present in some ceramic brick units. “Brown stain”, on the other hand, is mostly the result of manganese deposits.

Studies have shown that even very small quantities of water-soluble salts in the masonry may lead to efflorescence. The amount and character of the deposits vary according to the nature of the soluble materials and the atmospheric conditions.

Efflorescence is particularly affected by temperature, wind, and humidity. For example, in the summer, even after prolonged periods of rain, moisture evaporates so quickly that only small amounts of salt are transported to the surface.

During the winter, however, slower rates of evaporation lead to the migration of salts to the surface. Normally, with the passage of time, efflorescence becomes less prominent unless there are external sources of salts.

In most cases, efflorescence-causing salts are from the building materials used during construction, namely the masonry units and the mortar. Sodium and potassium hydroxides are commonly present in Portland cement and may cause some efflorescence during the first year after construction. This is known as “building bloom”, a condition that typically disappears after a short while.

Sources of Moisture

After the initial construction, as the masonry dries out, the exterior walls may display “building bloom” for the first few months. Typically, rain will remove this efflorescence and after one or two seasons, the blooming effect will disappear. However, where efflorescence persists, the continuous sources of moisture should be identified and controlled.

Water is the solvent for the efflorescence-producing salts. It is the vehicle by which the salts are transported to the surface where they accumulate as the water evaporates. The primary source of moisture is rainwater, particularly driving rains which deposit substantial amounts of moisture in the masonry walls.

Another major source of moisture is the leakage of moist air from the building interior. Such leakage is frequently possible due to discontinuities in the air and vapor barriers which will permit the exfiltration of moisture-laden air through the exterior wall components where they will condense on colder surfaces. Such moisture then migrates to the masonry surface by capillary action.

Air leakage in buildings can occur at sills, headers, and around rough openings cut to accommodate doors and windows, around plumbing stacks, and openings for electrical outlets. It can also occur at the top of partitions, where the vapor barrier is frequently discontinuous.

Is it Harmful?

In general, efflorescence in the form of surface deposits is not harmful to the masonry walls, but the disfiguring staining is annoying to owners and may affect property and rental values. If efflorescence persists beyond the initial period of “building bloom”, the sources of moisture must be investigated. Where abnormal wetting occurs due to poorly located drains and scuppers, missing copings and drips, or deteriorated caulking, these deficiencies can be readily rectified.

Where efflorescence is caused by air leakage, remedial repairs are frequently difficult to carry out and expensive since they entail the repair of air and vapor barriers and involve the interior finishes. Therefore, the advice of a professional engineer specializing in building science issues should be obtained for a careful assessment of the as-built conditions before remedial actions can be formulated.

While a number of surface treatments are commercially available to help control efflorescence, they should be used with caution. Most surface treatments act as water repellents which reduce the formation of efflorescence. This is partly due to the fact that less moisture is able to enter the masonry and partly due to the evaporation of soluble salts occurring just behind the treated surface layer, and this is where serious problems can occur.

As the salts crystallize and accumulate behind the treated surface layer, pressures can build up which may lead to spalling of the masonry units. Therefore, surface treatments may be successful only if they are carried out in conjunction with other measures that will control the amount of moisture entering the masonry from the interior.

Removing Efflorescence

Once the cause of the efflorescence is corrected, the removal of the deposit is relatively easy, since most efflorescing salts are water-soluble. In general, efflorescence can be removed by dry-brushing followed by flushing with clean water. If this is not satisfactory, walls can be washed with a five to ten percent solution of muriatic acid. It is always advisable that a small inconspicuous test area be tried first to determine whether etching or another discoloring will occur. After the acid treatment, the surface should be immediately and thoroughly flushed with clean water.

If chemicals are used, shrubberies and plantings along the building perimeters should be well protected or removed. It is also advisable to ascertain that the contractor assigned to this work is experienced and to check a few references. Acid treatment of masonry walls can do more harm than good if wrongly applied.

Cases & Conditions of Efflorescence

White powder on walls, white dust on walls, white powder on the brick interior, white stuff on a brick wall, white stuff on walls, etc. Contact us for the complete solution to this problem or call Keller Engineers now.


1. What is the white powder on my interior bricks?

The white powder on your interior bricks is likely efflorescence, a buildup of salt and minerals that occur when moisture seeps through the brick. You can this remove with a stiff brush or hire a professional to clean it. It’s essential to fix any underlying moisture issues to prevent further buildup.

2. What causes white residue and fluff to form on bricks?

The white residue and fluff on your bricks may be efflorescence, a buildup of salt and minerals that occurs when moisture seeps through the brick. This is needed to identify the address of any stuffiness-related issues to prevent further buildup. You can remove it with a stiff brush or hire a professional to clean it.

3. What are the white streaks or spots on my painted walls that resemble chalk marks?

The white chalky marks on your painted walls are likely caused by efflorescence, a buildup of minerals and salts. This is often caused by moisture seeping through the walls. To remove the white chalky marks on your painted walls, you can either use a stiff brush to clean it yourself or hire a professional. It’s essential to fix any underlying stuffiness issues to prevent further buildup.

4. What are the white fuzz on my brick wall and the white powder on my walls?

The white fuzz on your brick wall is often caused by efflorescence, which is a natural process where moisture seeps through the brick and evaporates, leaving behind salt deposits on the surface. These deposits can form a white, fuzzy growth on the brick. To remove it, you can use a solution of bleach and water and a stiff-bristled brush to scrub the affected area.

If you notice white powder on your walls, there are several possible causes. Dust and debris can accumulate over time and create a powdery appearance, while mold growth can also lead to a white powdery substance on walls. Low-quality paint or improper painting techniques may also result in a chalky white powder on walls. Identifying the cause of the white powder is important in determining the most effective solution. To get rid of the white powder on your walls, you can start by using a vacuum or duster to remove any loose debris. A possible revised version could be: If the white powder or fuzz on your walls cannot be removed by cleaning, it may be necessary to repaint the affected area with high-quality paint. Identifying the root cause of the issue is crucial to prevent the white fuzz or powder from recurring on your walls or brick wall.

5. What does the white fluff on my walls indicate?

The white fluff on your walls is likely to mold or mildew. It can appear due to moisture buildup, poor ventilation, or water leaks. This is important to address this issue promptly to check for further damage and ensure a healthy living environment. Consider contacting a professional for assistance.

6. What could be the cause of the white substance on my walls?

The white substance on your walls could be efflorescence, a common issue caused by salt deposits. It occurs when water infiltrates the walls and evaporates, leaving behind the salts. It is often a sign of water leakage or moisture problems. Assess your plumbing, roof, or any areas where water could be seeping in. This is suitable to consult a professional to identify and address the basic cause to prevent further damage to your walls.

7. What causes the appearance of white powder on my concrete after rain?

The white powder you see on your concrete after rain is called efflorescence. This takes place when water volatilizes, leaving behind salt remainder from within the concrete. While this is generally harmless, it can be unsightly. To minimize this development, ensure good drainage, seal the concrete, and maintain proper ventilation. If you have concerns or need expert guidance on managing it effectively, This is suitable to seek advice from a professional in the field.

8. What leads to the formation of white film and patches on painted walls?

The formation of white film and patches on painted walls can be allocated to several factors. One common cause is the collection of dust and dirt over time. further moisture or water leaks can result in efflorescence or mold growth, leading to white spots. Poor-quality paint or unsuitable surface preparation can also contribute to this issue. Regular cleaning, addressing moisture problems, and using high-quality paint can help prevent and reduce the surfacing of white film and patches on your walls.

9. Can white marks on brick walls be harmful to my health?

Flowering is a natural process that creates white marks on brick walls when moisture dismisses and leaves behind minerals on the surface. While this is not harmful, it can be unattractive and may signal underlying moisture problems. This is important to identify the source of the moisture and address it to prevent future damage. A professional can offer guidance on how to address the issue effectively.