Protecting Your Walls, III by Barbara Jennings
Efflorescence Ruining Your Walls, Part III?
You don't want to apply acid to brick masonry without previous wetting as it can cause "burning" or
discoloration of the brick. It can also eat into the mortar - not a good thing.
There are several types of procedures that are commonly used to remove efflorescence from masonry, concrete and stucco. When efflorescence is caused by soluble
alkali salts, the salts will dissolve again in water that is put on the surface and migrate back into the wall. But obviously it can return. Blasting and chemical treatments have
been found satisfactory in removing efflorescence from the face of concrete walls.
However, if calcium carbonate or calcium sulfate is the main component of the efflorescence, it adheres itself strongly and is much more difficult to remove.
Typically one would saturate the masonry wall thoroughly with water. Then wash the wall with dilute muriatic or phosphoric acid. Follow that immediately with an alkaline wash and
then rinse the wall with plain water.If the coating is largely calcium carbonate or calcium sulfate, it adheres
rather strongly and is difficult to remove.
Suitable acid/water formulations would be 5 parts acid to 100 parts water or 20 parts vinegar to 100 parts water. A professional should be consulted, however, to be safe.
One could use diluted household ammonia as a suitable wash.
Our advice is to trust a professional for these types of services. Great care should be taken when applying acids to cement products.
Acid attacks not only the calcium carbonates and calcium sulfate efflorescence, but it also attacks other compounds in the area as well. It can produce calcium salts such
as calcium chloride. This is why it is important that all acid be neutralized with an alkaline rinse before it can attack other compounds.
Stopping Efflorescence From Returning
Summary:Obviously since movement of salt bearing water is controlled to some extent by weather and we have no control over weather,
there are certain elements that cannot be controlled. Whenever it rains, it subsequently dries out and that's when the salt deposits appear. Another factor is the porosity of the
When any structure is first built, that is the time to select one of the following precautions:
- Materials with low potential efflorescing salt content.
- Materials with low water-cement ratio.
- Proper application and curing techniques.
- Proper moisture barriers.
- Quality workmanship.
Architects and contractors should protect the structure against excessive dampness. Protective sealant coatings are now used commonly to prevent water penetration
or moisture from entering exterior walls. But they will be unable to stop wicking and capillary action.
But the advantage of sealing the surfaces and thereby preventing normal movement of these salts can cause a potentially disruptive buildup beneath the surface.
A wall needs to be able to "breathe". Cautions should be taken when selecting sealers so that the sealer doesn't interfere with this. This is another reason why you should
hire an experienced applicator who is familiar with the materials. One can also contact the manufacturers to get advice on what they would recommend in using their
The results one can get from sealers and coatings is very broad. Gather up the facts before you proceed.
Here are Some Recommendations to Control Efflorescence
- Ground water must drain away from the structure.
- Hose bibs should not be dripping and sprinklers should be directed away from
- Proper ventilation of the structure. (Exhaust vents through the roof, not in
the attic). Prevent moisture from venting through the walls, which will result
in paint, stucco and framing damage. The walls must have proper vapor barriers.
- Install rain gutters and downspouts so that the water will drain away from
- When no weep screed is present you may want to install one and/or seal the
exterior walls to the foundation with tar or hydraulic cement.
- When painting stucco, consider using an epoxy fortified acrylic primer as a
- For a stucco finish coat a high quality elastomeric coating system is
- Consult a professional before doing anything.
Return to Part II
Return to Part I
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