FAQS

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.

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.

Preventing Efflorescence From Coming Back.

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.

For technical services, please call Combocrete International Products Company at (852) 2869 0228.

Essentially, clear waterproofing products are either water based or solvent based. KL-23, KL-25, KL-33, AG-11, AG-13, KL-35 and NP250 are water based products.

A short-form answer to this problem does not exist. Concerning product differences, with respect to carrier bases (solvent vs. water), the first notable difference is price. Solvent based products are certainly more expensive than the other water based products. Concerning differences in application, water based products may have a tendency to 'blush' or 'cloud' if misapplied to a dark brick substrate, that is why Combocrete hesitates to recommend the application of water based materials to brick or brick veneer substrates. While, on the other hand, Microcrete and Stain-Blok products water-based products perform quite well on these substrates. One very important comment concerning the difference between water and solvent based products .... you must understand that all clear liquid waterproofing products are designed to resist the penetration of water into the substrate. Application of a second coat of water based product, therefore, would be impossible since the first coat would prohibit, or repel, the second water based coat from penetrating the first coat. The attempted second coat would simply dry on the surface and eventually turn into a chalky residue.

Typically, the following substrates will be specified with  clear water repellent: Concrete Block, Brick, Brick Veneer, Plaster/Stucco, Cast In Place Concrete, Tilt-Up, and Stone (granite, marble, limestone, etc.).

By definition, concrete block is a manmade concrete masonry unit, or CMU. Usually rectangular in shape, concrete blocks normally feature hollow cores and are stacked upon one another. As the blocks are stacked, they are held together by mortar, and as the wall is being erected the hollow cores are filled with grout in order to strengthen the wall as it takes height. Concrete block is manufactured in a number of architectural styles such as split face, fluted, ground face, etc. Concerning waterproofing product selection with reference to concrete block, one of two materials should always be specified.... either Combocrete KL-23 or Combocrete Stain- Blok. The essential difference between these two products is warranty duration. While Regular features a 5-year warranty, the Blok-Lok warranty may be extended to 10-years.

Let us first address the types of brick and brick systems which are usually encountered. Brick can be manufactured in a number of fashions, ranging from full-face new brick, to brick veneer, clay brick, used brick, colored brick, brick pavers, and many more. The type of brick utilized or the method in which it is erected will have no effect upon selection of waterproofing material. Microcrete or Stain-Blok. Brick, of course, is composed of a denser material than concrete block; therefore, the permeability of the substrate will differ drastically. In other words, it takes longer for a liquid to soak into a dense surface than it does a porous material. Due to its specific design for porous surfaces, water based materials will not completely penetrate typical brick and may result in 'whiting or blushing' of the brick wall.

Unique in their nature, these methods of construction are widely used in large industrial, commercial and office projects. Cast-In-Place and Tilt-Up construction specifies the use of solid concrete as the exterior substrate. Concerning pre-cast construction, large concrete panels, or wall sections, are either pre-cast at the factory or cast on site and then tilted up into their vertical position. Cast-In-Place also features a solid concrete wall surface, but instead of tilting up the panels, wood or metal forms which have been built around proposed wall areas are filled with liquid concrete and, consequently, the wall actually cures or sets-up in place.

Frankly, due to their density and absence of mortar joints, these substrates rarely leak except where they crack. Architects, therefore, rarely specify an exterior waterproof coating material application. They do, on the other hand, often specify exterior sealers, such as Combocrete Color-Lok KL-33, which act to protect the wall from staining. Moisture and rain will, of course, penetrate the substrate, but due to the density and thickness of the wall itself, will not travel into the interior of the building. There are, however, other considerations which must be addressed.

Although leakage will not occur, rain contains a number of airborne pollutants and penetration into the substrate will ultimately result in staining and efflorescence as the moisture escapes the substrate during the drying process. The application of Combocrete Kl-25 will prevent the intrusion of moisture and subsequent staining. Although water based, Combocrete Kl-25 has been formulated to penetrate denser concrete substrates.

Absolutely. Have you ever noticed the effect created upon a piece of sandblasted marble, limestone or granite after it has been sprayed with water? A very light material will take on a dark gray or black appearance after the water has penetrated! Yes, moisture will indeed penetrate these substrates and, compounding this porosity, is the fact that some marble, limestone and granite panels are usually a mere 1 to 1.5 inches thick.

It certainly does not take long for absolute water transmission through the substrate. Cautionary note, test the application of any material upon these substrates, as they may effect the appearance of the stone. Due to its specific formulation, KL-25 is normally recommended for stone applications. A small test sample should always be applied prior to commencing the entire application.

No, in most cases the painting or waterproofing sub-contractor applies these products. Concerning equipment, utilization of a high-volume, low-pressure airless paint spraying system is recommended. Painters usually possess this type of equipment. For small applications, a garden type sprayer may be used; however, do not attempt application with a paint roller or brush.

Absolutely not! New masonry or concrete must be allowed to cure, or dry, for thirty days prior to application.

Allow us to address the moisture related issues first. Even if the wall has cured for the prescribed period of time, the substrate should be allowed four to seven days drying time following rainfall or power-washing. Never allow the application of these products if rainfall is imminent. Concerning another pre-application issue, it is the responsibility of each Account Manager to inspect the substrate and associated areas prior to product application.

Mortar joints must be inspected to assure proper tooling (no bee holes or shrinkage cracks), the roof cap must be properly installed, parapet walls must be properly addressed, and the substrate must, of course, be clean and dry. Only after such time that all pre-application deficiencies have been corrected will the sub-contractor be authorized  to proceed. As a rule, all pre-inspection memoranda are directed to the sub-contractor and general contractor in written form.

First of all, clear liquid waterproofing products are not designed to function in below-grade applications. Secondly, liquid waterproofing materials are not designed to fill holes or voids in faulty mortar joint areas. These products are designed to penetrate the substrate, not to create a surface film or sealant coat. As previously discussed, care should be taken to assure the proper tooling of mortar joints.

Lastly, liquid waterproofing products do not demonstrate maximum efficiency under standing water conditions. Product application, therefore, upon horizontal masonry surfaces is not warranted. As an example, typical rainfall upon a masonry window ledge will result in an average of one-eighth inch of standing water during the storm.

One must thoroughly understand the dynamics behind the penetration and resultant performance of clear liquid waterproofing materials. As discussed else where in this training manual, Combocrete products feature the exclusive Micro-Lok chemical reactive characteristic. This chemical interaction within the substrate that ultimately acts to repel water is only achieved by 100% penetration of our products into the wall surface. The solids which are dissolved within the liquid solution are carried into the substrate and, of course, the speed in which they penetrate depends entirely upon the density or porosity of the building material.