Probable Causes of Wall Leaks on Slabs

• Water finds its way onto a concrete slab by way of a wall in several different ways. Plumbing problems in connected pipes that run through wall voids are one cause of leaks on a concrete slab. Exterior water sources will also appear as interior water intrusion. These sources include improper grading of soil around the foundation, improper foundation drainage, rain gutter and downspout malfunctions, and broken sprinkler lines or overwatered flower beds located near the foundation. Insufficient curing of a concrete slab after it is initially poured will also lead to constant moisture inside the house, including wall framing and paneling or drywall.
  
  

Basement Slabs

• Water intrusion through a basement foundation is, unfortunately, very common. The construction of a basement includes the walls and a concrete slab floor, both of which are vulnerable to a variety of leaks. Foundation drainage problems, sewer system backups and plumbing problems with interior drainage all contribute to an increase in the groundwater levels around and below the basement foundation. This increase causes hydrostatic pressure -- force exerted naturally by water -- to rise enough so that water intrusion occurs. Basement walls sitting on a concrete slab are often the first spot where leaks of these types appear.
  
  

Plumbing Leaks in Walls

• The source of a water leak in an interior wall is often difficult to pinpoint. Pipes located within a wall void directly adjacent to standing water on a concrete slab may not even be the culprit. Gravity and interconnectivity are necessary for a plumbing system to operate properly, but these are the reasons that a water leak around a wall is often a tough problem to solve. For example, an upstairs bathroom sink that either leaks or that has high-humidity problems without proper ventilation may show evidence of a leak only on the ceiling framing of the room below until a water leak appears around an adjacent wall downstairs.
  
  

Leaks Under a Concrete Slab

• Main water supply lines that were installed beneath the concrete slab present a major plumbing problem. These lines, regardless of the material they were made with, are susceptible to ground shifts and settling that will cause a water leak under the slab. Pinhole leaks in copper pipes and cracks in galvanized steel pipes may go unnoticed until water pressure drops, the water bill increases dramatically, or eventually a water leak is seen on the floor or around a wall. Repair of this type of water leak is very expensive and, like any other major plumbing problem, should be left to a licensed professional to address.