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Principles
The most common cause of disputes and lawsuits in masonry (and other) construction is not the masonry itself or its construction; it is inadequate drainage (or other sources of water under foundations such as plumbing leaks).
Inadequate drainage (or other water sources) causes high and changing soil moisture, which causes loss of soil bearing strength and soil shrink/swell, which causes foundation movement, which causes masonry movement/cracks/failure. The primary cause at the root of this chain reaction is inadequate drainage, which is the most repeated source of disputes and lawsuits in construction, wasting billions of dollars across this nation. However, many people only address the symptoms (e.g. piering), which often is only a temporary solution.
Whether constructing siding, flooring, basement walls, retaining walls, free-standing walls of masonry (or other materials), proper drainage is critical to prevent movement. The only exception is foundations built into solid rock. However, even on solid rock inadequate drainage is a frequent cause of organisms (e.g. mold, rot, termites).
Therefore, adequate drainage will avoid disputes and lawsuits, and thus save enormous costs.
Code
As discussed in the first article (Jan/Feb 2008), knowing the rules and following them is a fundamental way to avoid disputes and lawsuits. If the governing building code is the International Building Code (IBC) or the International Residential Code (IRC), which it is for most of this nation, the drainage requirements (regardless of the foundation type) include:
- Ground 6” minimum below slab (IBC 2304.11, IRC R404.1.6).
- Minimum 6” fall the first 10’ out from and perpendicular to walls (IBC 1803.3, IRC R401.3).
- Minimum 2 percent elsewhere for surface drainage to a public outfall (IBC 1805.3.4, IRC R403.1.7.3).
- Minimum 12” + 2 percent elevation difference between slab and public outfall (IBC 1805.3.4, IRC R403.1.7.3).
If the building slab – existing or proposed – is not high enough to comply with the above, compliance often can be achieved with inlets and underground piping to a public outfall. However, this choice is less desirable because of added costs and the needed inspections and maintenance to keep underground drainage functioning.
Case Studies
The following examples (from the author’s cases) illustrate the impact of improper drainage on masonry construction. In each of these cases the author’s report resulted (some after deposition/trial testimony) in agreement between the parties to settle the case. But these costly litigations could have been avoided if there had been code complying drainage from the beginning.
Case #1: At a warehouse with cracked concrete masonry unit walls (below), the masonry was not the problem. The ground around the building was flat to negative (sloped toward building), which caused water to pond around the foundation. This set off said chain reaction that resulted in cracks in the foundation and masonry. One proposed solution was costly foundation underpinning (piling). However, this would have treated the symptom rather than the cause. The best solution was to reconstruct drainage slopes to comply with code. In this case, inlets and underground piping also were necessary.
Case #2: A new in-ground swimming pool had several problems, including rock sidewalk tilting toward the house. This negative slope violated building code and caused water to be directed into the house and into the clay soil under its foundation. This water entry damaged the visible masonry (interior and exterior) and caused foundation movement, which led to cracks in walls and walkways. The solution included: reconstruction of pool to comply with code drainage slopes and other requirements, underpinning of house foundation, and repairs to damaged areas.
Case #3: A residence suffered frequent flooding, and masonry wall cracks. The difference in elevation between the building slab and the public drainage outfall at the property corner was 21 inches. The distance from the most remote exterior foundation to the outfall was 150 feet. The code required difference in elevation between the slab and outfall was 48 inches. Therefore, the slab was built 27 inches too low. To solve the masonry, foundation and flooding problems, the slab needed to be raised or the outfall lowered, or a combination of both totaling 27 inches (and drainage sloped to comply with code).
These examples illustrate that masonry damage and consequent disputes and lawsuits often can be prevented if site drainage complies with code. Treating the symptoms of cancer and ignoring the disease does not make sense. It is equally illogical to treat the numerous symptoms caused by improper drainage and ignore the fundamental cause.
