hydrologue recognizes that moisture intrusion into buildings is one of the major problems faced by Southern California engineers, architects, homeowner associations, contractors and insurance companies. Problems that result from moisture intrusion can be extensive and expensive to remedy. And, it is a major cause of lawsuits against homeowner associations, real estate management companies, architects and developers. Research has shown that many people develop health problems from exposure to mold and mildew spores that result from moisture intrusion. hydrologue's experts have considerable experience in water intrusion investigation and remediation.

From our experience, the intrusion can result from diverse sources. Moisture can migrate up into a structure through a seemingly rigid and competent concrete foundation/slab causing water damage to carpeting, damaging hardwood and vinyl flooring by weakening the floor-covering adhesive or causing warpage or swelling. At the other extreme, if groundwater is present above a basement floor, the water can intrude into a structure through shrinkage cracks in poorly constructed concrete members, hairline cracks, and improperly sealed joints. Moisture can also intrude downward through a concrete roof structure.

Water vapor, leakage, and capillary action result in moisture intrusion into structures. Water vapor moves from one area to another whenever there is a difference in vapor pressure between two areas. If the groundwater table is above a basement floor, then the floor and walls of the basement are subject to hydrostatic pressure, and considerable amount of water can leak or flow through the wall cracks or joints. Similarly, capillary forces can cause moisture and/or water to migrate into a structure through hairline cracks in the concrete.

In Southern California, concrete flat slabs are commonly used in basements or subterranean garages. Pedestrian walkways, planter areas, and lightweight structures are commonly built on top of these concrete flat slabs. Moisture can migrate through the concrete flat slab and efflorescent can reduce the strength of the concrete. An associated problem is corrosion of metal pipes. A primary cause of moisture intrusion through a flat slab ceiling is the poor drainage condition of the flat slab surface and poor waterproofing of the slab joints. Among the efficient remedies that hydrologue employs in this situation is the installation of a properly designed subdrain behind the basement wall. The subdrain acts to lower the water table and prevent the buildup of hydrostatic pressure.

Also, internal or surface waterproofing agent may be installed. Several concrete admixtures can be used as internal waterproofing agents. Often an exterior applied waterproof membrane is used with varying efficiency on basement walls. Wall damage moisture that migrates through basement walls can damage wall coverings, such as wood paneling, and cause musty odors or mildew growth in the basement areas. As the water evaporates at the interior wall surface, dissolved salts in groundwater form efflorescence on the basement walls. The salt crystals can accumulate in cracks or wall pores, where they can cause erosion, flaking, or ultimate deterioration of the concrete wall when the groundwater contains sulfate. The process of crystallization often involves generation of swelling and considerable pressure. The loss of strength of concrete walls and ceilings can be evaluated by destructive testing of the concrete cores of the wall or ceiling or by nondestructive testing using a Schmidt Hammer or similar equipment. Some of the deficiencies that contribute to moisture intrusion through basement walls are:

We can investigate and quantify the water vapor flow rate through a concrete slab or wall. We utilize inexpensive methods to obtain vapor flow rate at different slab/wall locations at different times. We can determine whether there is an acceptable water vapor flow rate of less than 3 lbs./day. At 3 lbs./day or less, rubber, vinyl, or wood and carpet flooring can be satisfactorily installed. If the vapor flow rate, however, exceeds 5 lbs/day, remedial measures should be implemented.