Efflorescence

This is the second rainiest December in recorded history in Southern California. For those of us in the stucco business lots of rain can only mean one thing: EFFLORESCENCE!

This is the white powdery material we see on concrete, masonry, stucco and other substrates that are naturally high in alkaline. Usually about a week following the rains I get quite a few calls from builders and homeowners letting me know that “the lime is coming out of the stucco”! I patiently explain that these are naturally occurring mineral salts that are present in plaster, cement, stucco, mortar, stone, soil, water, and many other materials used in construction. In some cases the efflorescence can manifest itself as a “bloom” of white calcium carbonate and have a crust. The water soluble salts liquefy and as the wall dries the water migrates to the surface carrying the salts. The water turns to vapor and evaporates leaving the salts on the surface in the form of efflorescence.  We see it most often in new construction where the salts are in higher concentrations. But efflorescence can occur over time as long as the salts are present and the conditions exist for them to migrate to the surface. Slower evaporation also tends to allow more salts to come to the surface and obviously large amounts of rain exacerbate the condition. The good news is that these salts can be neutralized. Since these salts are by nature extremely high PH it is logical that a low PH solution (an acid) should be used to neutralize it. On a smooth wall or masonry you can use a soft brush and a mild solution of white vinegar and water to kill it. On tougher staining or textures that can be damaged by scrubbing then a stronger acid solution can be used. Be extremely careful however, acid can etch glass, kill plants and is very caustic and hazardous to use. One method for removal is to dry brush the calcium off and then flush the area with water.  This seems counter intuitive to add more water but since there is a finite amount of salt it does work. After cleaning a sealer can be used to stop water. Merlex’s Micro Seal is an excellent chemical for stopping water.  If the water cannot get into the wall it can’t carry the salts back out. So the next time it rains just get out the vinegar and don’t blame it on the lime!

Cracking In Exterior Stucco

Having been in the construction industry for over thirty years and at Merlex for close to eighteen I am usually asked the same questions over and over. Through the years I have written letters explaining certain conditions and tend to use the same ones for similar circumstances. There are published reports and industry associations from which I have drawn much information and technical data.  I have sold lath and plaster, drywall, metal studs, masonry and related tools and aggregates that have given me much experience in the construction of walls and ceilings. I have consulted on structural issues, fire ratings, and water intrusion problems. I now feel uniquely suited to answer questions and offer solutions about frequently asked questions regarding stucco, plaster systems and the building envelope. I hope that I can have some lively discussions and learn a few things both locally and within other regions about stucco and related products and issues.

Topic #1   Cracking in exterior stucco

The single most discussed topic in Portland cement stucco is cracking. I have spent countless hours and many thousands of miles looking at cracks which don’t seem to change much over the years.

No one can guess how much the stucco will crack in your home, building etc. There are many reasons for cracking none having anything to do with the quality of material, level of workmanship or knowledge of the builder. It does have everything to do with how much the structure moves. All the variables for structural movement are in play including geological conditions, wind shear, movement and shrinkage of framing members, weight on the building envelope (walls) seismic activity and any other cause of stress to the building.  It is advisable to discuss this at length with your structural engineer, architect and general contractor before proceeding with the plaster and stucco. There are certainly some technological advances in the plaster system that can reduce (not eliminate) the incidence of structural cracking. The base and mesh system is the newest and most effective solution to significantly reduce the incidence of cracking. This is an additional coat of material consisting of a polymer modified base coat with an embedded fiberglass mesh for added reinforcement. The benefit is twofold: The first is the modification of the additional cement with polymer to allow for some movement or elasticity in the material. The second part of the system is the mesh that works as a slip joint to arrest cracks that emanate from some underlying stress. You can find more specific information on the Merlex site on the technical bulletin for Basex and the Basex frequently asked questions sheet.

I hope that I hear from industry experts, product reps, or other areas with some novel solutions to this old problem.