Keeping a building dry is both an interior and exterior challenge. All buildings, regardless of materials and construction, are at risk of water infiltration and moisture build-up in basements, walls, ceilings, window wells and roof materials. 

This can cause problems ranging from structural deterioration of the building itself to health issues for residents. Locating and correcting leakage problems before they get to that point requires vigilance and a commitment by boards and managers to act quickly and decisively when one arises. 

The Origin of Leaks

Moisture shows up inside buildings in two main ways: in liquid form, known as ‘bulk water,’ or in the form of gas, called ‘vapor drive.’ Bulk water visibly flows, drips, trickles, and pools. Unless it’s the result of a burst pipe or overflowing appliance, it originates outside the building, entering through basements, failed joint seals, window perimeters, and roof transitions like chimney exit points, parapet walls, or where metal roofing material meets asphalt. By contrast, vapor drive originates inside the building, and is the natural movement of usually-invisible water vapor through building materials from warm, humid, high pressure areas to colder, drier low pressure ones. If water vapor gets trapped and accumulates inside a wall or ceiling (usually because of poor ventilation and/or insulation issues) this condensation can lead to mold growth, and eventual structural damage. 

According to Roy Spencer, president of Perma-Seal Basement Systems located in Burr Ridge, Illinois, “Water is the enemy of your home and building. It rots wood and concrete, brick and mortar. Also, because of the freezing/thawing cycle, when water gets in, the resulting ice expands to 10 times its liquid volume, which pushes against structural materials and creates more cracks. This can result in corrosion of steel structures and damage to interior finishes. If concrete is not waterproof, water will find its way to the steel rebar, making it expand and push out the concrete, creating a cascading series of issues, even to the point of injury from falling bricks, or even building collapse.”

Multifamily buildings are engineered to resist both bulk and vapor moisture, but according to Russ Fernandes, senior VP and owner of Becht Engineering BT, Inc. based in Warren, New Jersey, any structure can spring a leak. A building’s specific vulnerabilities depend on what it’s made of, and how (or perhaps how well) it’s constructed. “Any list of likely entry points will vary, based on the type of construction,” he says. “That said, one common source of leaks in any style of building is the failure to properly detail the penetrations of roofs and/or walls.” 

Penetrations are any spot on a roof or wall where there is an opening or gap created in a building envelope to allow services like pipes, cables, vents, and HVAC components to pass through from one side to the other. If these penetration points aren’t properly flashed and sealed, problems from both bulk water and vapor drive almost inevitably arise. 

According to Giulia Alimonti, vice president of Falcon Group/Falcon Engineering, a national firm with offices in New York, Florida, New Jersey, and Pennsylvania, “Any lack of continuity in a building envelope’s transition between different materials—metal window frames and the exterior brick façade, for example—can result in a breach, so there must be a sealant in between. This critical joint must be regularly inspected and replaced, because as the sealant wears out over time, that deterioration creates gaps between the brick and metal, which in turn allows infiltration of both air and water.”

Along with roofs and windows, basements are also fertile ground for water infiltration, explains Sushruth Keval, an associate with CTL group, an Illinois based engineering firm with offices in Chicago and New York. “One of the most frequent points of possible water infiltration is…the basement or other areas below surface level. Water intrusion through the walls or basement causes interior plaster damage and creates damp conditions that favors unwanted organic growth. Over time, trapped moisture can cause severe damage to the building components, especially when it repeatedly freezes and thaws.”

The Pillars of Waterproofing

According to Neil Rouleau, COO of Boston-based BRS/Building Restoration Services Corp. and BRS/Building RECON Services, proper waterproofing is centered on four primary pillars. “Structural preservation is the first pillar,” he explains. The second pillar, equally important, is the health and safety of residents. Trapped moisture fosters mold growth,” which in turn can cause or worsen allergies and respiratory illnesses like asthma, and are especially dangerous for the very young, the elderly, and anyone living with compromised immunity.  

“Preserving asset value is the third pillar,” Rouleau continues. “Unaddressed water infiltration leads to special assessments, and deferred maintenance can cripple property values. I’ve seen condominium owners unable to sell their units because a looming capital project to address leaks creates too much financial uncertainty for buyers. 

“Finally,” he notes, “hydrostatic pressure in basements is a fourth factor. Waterproofing isn't just about keeping moisture out; it’s about resisting the physical force of groundwater pushing against the foundation, which can cause structural shifting.”

Early Warning Systems

Since water infiltration is often invisible until it’s too late, how can you know there’s a problem before it gets to that critical point? According to Alimonti, the canary in the leaky coalmine is often drafty windows—especially in older buildings. Drafts and condensation around windows indicates that the window seals are breaking down—and if air can move through, eventually water will too, leading to all the costly headaches discussed above.  

According to Keval, when a leak is visible, “Professionals usually start by gathering patterns where residents see staining or peeling, when it happens after wind-driven rain or any heavy weather event. Next comes a focused engineering inspection of likely entry points, often paired with tools like infrared scanning or electrical impedance testing to narrow down where moisture is active. Repairs then target the source by restoring waterproofing and deteriorated masonry components. Post-repair water tests can then verify and confirm that the leak path has been addressed.”

Spencer points out that different parts of the building should be tackled individually. “There’s above and below grade,” he says. “Two very different areas. In a basement and/or crawlspace, which is a big area of concern, it’s a natural thing for water to pool. We look at the structure and how it’s made. With poured concrete, our inspection is focused on looking for cracks. We have to secure that to prevent penetration. Additionally, when you dig a hole—as for a basement, for instance—you get hydrostatic pressure from underneath, so most basements have a drainage system that empties into a sump pump. That’s what relieves the water pressure from leaking up through the floor. It’s imperative to repair cracks and holes and to have a functioning drain tile and sump pump system.”

“Today,” Rouleau adds, “a professional approach has moved away from ‘guess-and-check’ repairs and toward a scientific diagnostic approach, first by process of elimination. The goal is to understand why the building leaks before spending money on how to repair it. We use controlled water penetration resistance testing, applying water to specific exterior sites while monitoring the interior. Then we continue with directional testing, always from the bottom up to avoid ‘ghost leaks’ caused by overspray from above or adjacent areas. 

“Next,” he continues, “we use moisture mapping, employing moisture meters to determine if materials are absorbing water even before a visible drip appears. And finally, we do a root cause analysis. Once the source is isolated, we can provide repair budgeting and options.”

New Technologies

That more scientific diagnostic approach often makes use of new technologies that enable engineers to pinpoint the source of a leak with near-surgical precision. 

For example, infrared thermography can ‘see’ through solid materials and detect temperature anomalies without damaging the materials themselves. Since wet insulation retains heat longer than dry materials, moisture trapped behind walls or under membranes shows up in thermal imaging, and can be mapped without invasive cutting, although often some limited sampling is needed to validate results. Thermal imaging can also help identify air leaks, as well as thermal bridging, when heat transfers across a metal stud, for example, and provides a way to find pinhole breaches in flat-roof membranes that are invisible to the eye. 

Effective monitoring technology is another powerful tool in the battle against leaks and the damage they cause, says Spencer. “The newest thing in the industry is called the Basement Defender, which is a smart home component that can test sump pumps every day using WiFi. The sump pump is the most critical component in the protection system, and this new technology will report any problem with it. Sump pumps are used in any building with a basement—big apartment buildings included. They all need this.”

Leak prevention tech also extends to building materials themselves. For example, modern crystalline technology has enabled the development of admixtures that make concrete inherently water-resistant by plugging pores. This is particularly effective for interior foundation walls, preventing groundwater infiltration without the massive expense of exterior excavation. Further aboveground, self-gasketing roof and wall membranes are air and water barriers that ‘self-heal’ or seal tightly around fasteners and other surface penetrations, keeping moisture out and ensuring the assembly’s integrity.

The Price of Doing Nothing

Like a broken tooth or a pest infestation, leaks don’t get better on their own; quite the opposite, in fact. Ignoring leaks can result not just safety and health issues, but financial and legal consequences as well. 

“By the time a leak is visible,” says Rouleau, “the internal sheathing and structural studs have often been saturated for a long period, leading to significantly higher repair costs than if the issue were addressed early.”

Keval agrees. “The longer water is allowed to travel and spread, the more likely you’re looking at more disruption and higher costs,” he says. “Over time, repeated water or moisture infiltration can accelerate cracking and deterioration, making repairs more extensive and expensive.”

And if that’s not enough to convince you of how crucial it is to address leaks swiftly and professionally, adds Rouleau, “Unresolved leaks can lead to litigation, insurance premium hikes, and a total loss of marketable title during property transfers.”

Winning the Battle

The natural forces and phenomena that lead to leaks and water damage aren’t going anywhere. That’s why a regular program of inspection, detection, and correction will help keep your building exterior intact and your building interiors dry and cozy. According to the pros, having your individual building components inspected every three to five years (unless required more frequently by law) by competent, experienced professionals and following their recommendations is reasonable. 

Structural problems and façade impairment should not be taken lightly. When it comes to leaks and water damage, proactive detection and swift remediation are key to maintaining both safety and value for your building or association. 

A.J. Sidransky is a staff writer/reporter with CooperatorNews, and a published novelist. He may be reached at alan@yrinc.com.