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Sulfate Attack
In the past few years it has become increasingly obvious that the foundations of many homes and other buildings in certain regions of California are slowly, irreversibly being destroyed by a white, powdery substance called sulfate. It's an unpredictable, pernicious agent that seeps into the foundation of a building. Some areas appear to have higher levels of sulfates than others, but much of California has soils of a marine origin containing measurable levels of sulfates. Because sulfates can destroy the structural integrity of a home and undermine its long term performance - and construction strength - homeowners with sulfate problems are filing construction defect lawsuits in increasing numbers to recover damages. Some of the most commonly asked questions about sulfates are answered below.
What is sulfate?
Sulfate is a naturally occurring mineral salt compound. In California, soil deposits are often rich in gypsum, and are laced with gypsum veins. Gypsum is a form of calcium sulfate (CaSO4). Sulfate deposits in soils with a marine origin are also high in sodium sulfate (NaSO4) and magnesium sulfate (MaSO4). When the soil becomes wet from irrigation or rainfall, the sulfates dissolve in the water and seep into the porous concrete. Once the deterioration starts, the damage to the concrete cannot be reversed.
When and where do symptoms of sulfate attack show up?
Sulfate damage typically appears in the form of hairline cracks called "etching", or white, powdery stains referred to as "efflorescence." The best place to look first is on the garage floor or driveway, or along the exterior foundation. However, not all white powder is sulfate. As the sulfate attack worsens, other parts of the home's foundation will show signs of efflorescence and etching. It can also appear on patios, driveways, swimming pools and other so-called "hardscape." If you are suspicious and want to know for sure, a geotechnical firm can take a sample from your home and analyze it.
How many homes are affected by sulfate damage?
Possibly tens of thousands of homes, apartments and condominiums along the coastal and inland areas of California are built on sulfate laden soils that can, under certain conditions, destroy the concrete foundations. One expert said sulfate cases could cost the Southern California homebuilding industry - or more precisely, their insurance companies - as much as the Northridge earthquake.
Is it strictly a California problem?
High sulfate levels seem to be concentrated in areas once covered by seawater, which created large deposits of gypsum. Gypsum is a common source of sulfate. Many parts of California were once covered by the ocean; some of these areas have high levels, some have low levels, and some are sulfate free. It depends on the type of soil and other factors. Soils rich in sulfates are found throughout the United States, and throughout the world.
What does the Uniform Building Code (UBC) say about sulfates in the soil?
The Uniform Building Code requires that concrete used in soils with moderate to severe levels of sulfates be of a special type and mixture that retards seepage by sulfate-ladened groundwater, which eats away the cement "paste" that holds the concrete together. If the Code is followed, the concrete will be more "dense" than normal and thus retard water seepage.
What are builders required to do to determine if sulfates are in the soil on which they want to build?
Before beginning construction, builders are required to conduct soil tests that measure sulfate content. Reports on such tests should be on file with local building departments or environmental management agencies. If a housing project is newer, the builder may still retain a copy of the report. Ask to see it.
Exactly what does the Uniform Building Code require if sulfates are found in the soil?
Since 1979, the Uniform Building Code has required that a special Type V cement be used in high-sulfate soils, and that a lower water-to-cement ratio be used to maintain a proper level of density in the concrete after curing. Dense concrete stops groundwater from seeping in; it's the water that carries the sulfates. According to the UBC, the ratio of water-to-cement in high-sulfate soil conditions should be no more than 0.45. However, in many cases that have been investigated, the ratio is more like 0.65 to 0.70, or 50% in excess of maximum. The result is concrete with an interconnected pore structure, and therefore not dense. The denser the concrete, the less likely the water will seep in.
Don't all builders do these tests and comply with the UBC requirements?
Certainly, many builders have complied with UBC sulfate requirements. However, concrete used in construction of potentially tens of thousands of California homes built on high-sulfate soils since the mid-1980s does not meet Uniform Building Code standards, creating a defect that can result in the concrete's decomposition. One reason is that contractors and suppliers of concrete ignored the UBC requirements. Compounding the problem, those contractors who poured concrete at building sites frequently mixed in additional water to make installation quicker or easier.
What happens when sulfates get into concrete?
As the sulfate infiltrates concrete, it combines with the C-S-H, or concrete paste, and begins destroying the paste that holds the concrete together. As sulfate dries, new compounds are formed, often called ettringite. These new crystals occupy empty space, and as they continue to form, they cause the paste to crack, further damaging the concrete. The concrete weakens and the paste continues to separate and crack. Consequently, the concrete becomes increasingly permeable, allowing in more and more water filled with sulfates. Over time the process accelerates dramatically. The excess water content and porosity also begin to rust away the anchor bolts that tie the home's structure to the foundation.
What's the worst that can happen?
Eventually, the concrete foundation disintegrates and turns to rubble. This condition, coupled with the rusting structural ties and anchor bolts, puts a home and its occupants at greater risk from earthquakes, high winds and other destructive forces of nature. According to the National Association of Home Builders, the useful life of concrete should be about 150 years; however, left unattended, sulfate attack can cut that life span to 15 years or less.
The information given above is necessarily general in nature and is not intended as legal advice.The matters discussed are subject to great complexity and subtle gradations of application depending on their specific factual context.There is no substitute for sound legal advice from trusted legal counsel in light of specific facts.
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