Efflorescence is a deposit of soluble salts, usually white in color, which sometimes appears on the surface of masonry or concrete construction. Often efflorescence is apparent just after the structure is completed, when the builder, architect and owner are most concerned with the appearance of the new structure.

There is no need to panic; however this phenomenon has a simple explanation and an equally simple solution. A combination of circumstances causes efflorescence:

1. First, there must be soluble salts in the masonry.
2. Second, moisture must be present to pick up the soluble salts and transfer them to the surface.
3. Third, some force, evaporation or hydrostatic pressure must cause the solution to move.

If any one of these conditions is eliminated, efflorescence will not occur. In most cases, salts that cause efflorescence come from construction materials, masonry units or mortar.

There are occasions when efflorescence occurs from a chemical reaction between the chemicals in the materials and the chemicals in the atmosphere. Efflorescence is particularly affected by temperature, wind and humidity. It is more common in the Western States during the winter months when more rain is present and a slower rate of evaporation allows migration of salts to the surface. Moisture may also enter a masonry wall due to vapor from the interior of a building and accumulate within the wall as it condenses, or rainwater may enter the masonry during construction. Proper protection can help alleviate this problem.

Waterproofing materials are designed to inhibit efflorescence by preventing rainwater from entering the wall. However, they have no effect on efflorescence caused by construction moisture.

Efflorescence is a normal construction "phenomenon". Once the building is waterproofed we can expect a certain amount of efflorescence caused by residual construction moisture. Once that efflorescence is removed we expect no new efflorescence. In other words no new water is allowed to enter the walls.

Waterproofing materials are designed to prevent the formation of efflorescence caused by rainfall. They are not designed to "hold in” efflorescence caused by construction moisture as this "holding in” could cause pressure buildup in the wall, causing spalling of the surface.

We recommend a light dry sand blast where possible or removing the white powder with a stiff bristle (not wire) brush. Also recommended is the use of high-pressure chemical cleaning equipment designed to energize the water by heating it. The force of the hot water and chemical hits the substrate with needed impact to remove efflorescence and mortar stain without damaging the masonry surface.

Allow masonry to dry sufficiently before applying waterproofing! Three or four days may be required, depending on weather conditions. In general the safest practice is to apply waterproofing as soon as the surface is dry to a depth of at least one half inch. Residual moisture in the wall will escape to either the inside or outside, (the warmest side). Efflorescence deposited on a waterproofed surface is more easily removed. In addition, new waterproofing will penetrate through existing efflorescence.

If, however, a building is erected during late spring, or early summer, a more practical approach is to delay waterproofing until after the walls have thoroughly dried and have been cleaned. Naturally, “dry” cleaning is preferable. If efflorescence reappears, it tells you that there is leak in the building. When the leak is found and repaired, the cause of the efflorescence problem is removed.

All masonry materials are permeable to water to some degree. The most permeable materials being concrete masonry, the least permeable being stone, glass block and glazed tile with the various types of clay masonry products (bricks, tile, etc.) falling somewhere in between. What all masonry materials have in common is that they are "held together" by mortar, which is generally very permeable and can allow leakage regardless of the density or relative impermeability of the masonry units themselves. Masonry structures are commonly waterproofed for one or more of the following reasons:

1. To prevent moisture damage to interior walls, floors and ceilings.
2. To preserve insulation values.
3. To prevent rusting of structural steel components.
4. To prevent freeze damage.
5. To prevent unsightly efflorescence and preserve the exterior appearance.
6. To otherwise preserve the masonry from deterioration due to moisture.

Nearly all-concrete masonry buildings are waterproofed in some way at the time of construction. Those that aren't are usually waterproofed soon after the first rainfall! Many brick buildings, on the other hand, are not waterproofed at the time of construction. A trained eye can usually discern which were not, merely by casually observing them a year or two after construction.

If brick veneer is attached to steel stud backup there should be no question that it must be waterproofed to help protect the integrity of the system. This has been a controversial opinion for several years but time and experience are proving the pro-waterproofing opinion correct. A recent newspaper article tells of the sad plight of a manufacturer of mortar additive who is defending 28 lawsuits due to corrosion of metal supports and anchors causing cracking, falling bricks, sagging walls, etc. Since the cost of waterproofing is so minimal when compared to the risk factor, it certainly seems prudent to waterproof. Please note, however, that waterproofing is only part of the answer. Sound design details and masonry workmanship play a most vital role.

For architectural above grade masonry the clear, penetrating chemical treatments are most commonly used. These are invisible treatments and can be very effective. Due to deep penetration their hydrophobic protection is deposited beneath the surface where weathering cannot affect it. Clear "coatings" is a misnomer often applied to these penetrating materials. They do not create a coating film across the surface of the masonry and thus should be called penetrants. There are, however, clear coatings, which are often mistakenly relied on for waterproofing. These coatings can be initially effective as waterproofers on the denser substrates. Their inherent weakness is that their protection is primarily on the surface in the form of a thin film. This film is susceptible to the ravages of weather, physical abrasion and minute film cracks all of which can expose a thirsty substrate. It is advisable to always apply a penetrating chemical treatment first. If a clear "coating" is applied first and is only partially effective it can create some very serious problems.

For example:

1. It will inhibit the penetration of a penetrating treatment applied as a remedial measure.

2. It could require sandblasting for removal in order to correct a waterproofing problem.

3. A truly impermeable film can trap moisture, and efflorescence created by this moisture, behind the film requiring costly removal, which could deface the building. Even worse we have seen cases of severe spalling (sluffing off the surface of the substrate) caused by vapor pressure build-up behind impermeable clear films.

Other types of "coating" systems are block filler and paint, textured coatings, cementitious masonry coatings and elastomeric coatings. These systems are less common on architectural masonry and are more often used on industrial type construction. They are certainly much more resistant to weathering and physical abrasion then the thin films. They, with the exception of elastomeric coatings are, however, susceptible to cracking.

Often a penetrating chemical waterproofing is specified as a first coat. Since it becomes an integral part of the masonry it can act as a second line of defense against moisture intrusion in case of a failure in the surface film.

Yes, integral water repellent admixtures are available to be incorporated into the concrete masonry mix by the manufacturer at the block plant and into the mortar, by the masons’ helper, at the time of construction. While these can be of some benefit in inhibiting the formation of efflorescence, it is the opinion of our industry that they cannot be relied on as the sole line of defense against moisture intrusion due to the likelihood of human error. While topically applied, systems are commonly warranted by both manufacturer and applicator, we know of no such assurance of performance of the admixtures.

Yes, integral water repellent admixtures are available to be incorporated into the concrete masonry mix by the manufacturer at the block plant and into the mortar, by the masons’ helper, at the time of construction. While these can be of some benefit in inhibiting the formation of efflorescence, it is the opinion of our industry that they cannot be relied on as the sole line of defense against moisture intrusion due to the likelihood of human error. While topically applied, systems are commonly warranted by both manufacturer and applicator, we know of no such assurance of performance of the admixtures.

Most of the masonry waterproofing problems we have inspected in the past 35 years are directly attributable to horizontal surfaces. Our answer is: avoid horizontally exposed masonry as much as possible. Clear chemical sealers are much less effective on horizontal surfaces than on vertical surfaces. Thus, if a clear sealer is to be used for waterproofing on a masonry structure the following suggestions are offered:

1. Tops of masonry walls should be protected with either a sheet metal cap or a membrane type material such as an elastomeric coating tinted to match the masonry. If a metal cap is used, we recommend "sanding" seams and a minimum of 3" of skirt over the masonry surface.

2. Avoid ledges and recesses.

3. Sills, if unavoidable must be adequately sloped.

4. Raked mortar joints should never be used on exterior surfaces. A "V" tooled joint can provide the same visual effect and can be effectively waterproofed.