Water ingress—also known as water intrusion—is a pervasive threat to the health, safety, and longevity of buildings. The term “water ingress into buildings” refers to the unintended penetration of moisture into a structure through its external envelope, which includes walls, roofs, foundations, doors, and windows. Once moisture finds a way inside the consequences can be extensive, ranging from cosmetic blemishes and energy inefficiency to structural degradation and health hazards, and these things are particularly true for older structures. This article outlines the causes and consequences of water ingress and explores modern prevention and mitigation strategies, including advanced early detection technologies that are reshaping how building professionals manage moisture risk.
Causes and mechanisms of water ingress into buildings
A building’s envelope—including the foundation, walls, roof, windows, and doors—serves as a critical barrier protecting the interior from weather, temperature extremes, noise, and unwanted light. It prevents water intrusion, air leakage, and moisture penetration, safeguarding both the structure and its occupants. However, water can still breach the envelope through flaws in design, construction, or maintenance. Rain, melting snow, and groundwater are primary sources of external moisture that can cause significant problems if the envelope is compromised.
Roofs are especially vulnerable to moisture. Water intrusion often results from missing or damaged shingles, deteriorated waterproof membranes, or compromised flashing around chimneys, vents, and skylights. Blocked or damaged gutters and downspouts can worsen the issue by preventing proper drainage, leading to water accumulation near the foundation and increasing the risk of basement or crawl space seepage. Flat roofs are particularly susceptible to water ingress compared to pitched roofs, due to the possibility of water pooling if drainage systems are inadequate, poorly maintained or become clogged, resulting in significantly heightened risks of leaks through the roofing material. In contrast, pitched roofs facilitate the runoff of rain and melting snow, minimising prolonged moisture exposure and reducing the potential for water-related damage
Exterior walls are susceptible to moisture intrusion through a variety of pathways, including cracks in the masonry, gaps around windows and doors, and deteriorated seals or flashing. Over time, even minor and often undetected cracks can permit enough moisture to penetrate the wall assembly to cause significant damage. Aging masonry is particularly vulnerable if protective coatings or mortar joints have degraded. Foundations are also at considerable risk, especially in older buildings that lack modern waterproofing systems or in areas with poorly drained soils. In such conditions, hydrostatic pressure from saturated ground can force water through small openings or imperfections in basement walls and floors.
Internally, sources of moisture such as hidden plumbing leaks and elevated humidity from everyday activities—including cooking, bathing, and laundry—can result in condensation within walls and ceilings. Spaces that are inadequately ventilated or insufficiently insulated are particularly prone to this type of moisture accumulation.
Drone thermal infrared image of moisture in roof tiles
Effects on structures and occupants
Unchecked water ingress can have severe and far-reaching consequences for a building’s structural integrity and overall performance. Structural elements such as wood and steel are particularly vulnerable to moisture, which accelerates rot, corrosion, and a progressive loss of load-bearing capacity. Even concrete, often considered highly durable, is susceptible to water infiltration; over time, this can result in cracking, spalling, and significant weakening of foundations and structural slabs. These problems are often exacerbated in older buildings, where materials may already be compromised by age or previous damage.
Moisture intrusion also undermines important aspects of a building’s interior features and environment. Insulation and interior finishes can be significantly damaged, leading to decreased energy efficiency, reduced occupant comfort, and increased heating or cooling costs. Electrical systems are similarly at risk, as exposure to moisture can lead to short circuits, equipment failure, and even fire hazards. Persistent dampness also creates an ideal environment for mold and mildew growth, which not only damages building materials but also presents serious health risks—especially in properties with outdated ventilation systems or where remediation is difficult.
Finally, the financial impact of water damage is substantial: property values may decline, insurance premiums can rise, and owners often face costly repairs and restoration efforts.
Prevention and Detection Strategies
Effective management of water ingress into buildings begins with robust, preventive design and construction practices. Roofs should be engineered to shed water efficiently, with adequate overhangs and properly installed flashing to protect vulnerable junctions. Facades benefit from drainage and drying mechanisms, such as ventilated cladding or rain screen systems, which allow moisture to escape. Selecting durable, water-resistant materials suited to the building’s climate and exposure is essential, and all sealants and membranes must be compatible with adjacent surfaces and capable of withstanding environmental stress.
Further, regular maintenance of the envelope—repairing damaged mortar, resealing joints, and updating waterproofing systems as needed, ensuring that gutters and downspouts remain clear, and that site drainage directs water away from foundations, is critical. Where possible, upgrading insulation and ventilation can help manage internal moisture and reduce condensation. In high-risk environments, comprehensive waterproofing solutions and routine monitoring provide additional layers of protection.
When prevention fails, however, timely detection is crucial for mitigating the impact of water ingress, especially in older buildings where hidden vulnerabilities are common. Traditional inspection techniques—such as visual assessments for stains, peeling paint, or musty odors—remain important but are increasingly complemented by advanced technologies such as moisture meters, acoustic sensors, and tracer gas systems, which can help locate concealed leaks.
A notable recent advancement in building diagnostics is the use of drones equipped with thermal infrared cameras to survey exteriors and roofs. Infrared thermography detects often subtle differences in heat radiation that reveal the presence of water within structural cavities, walls, or roofing systems, frequently identifying problems before any visible symptoms appear. This technology enables rapid, cost-effective, non-invasive and safe inspections of even large or hard-to-reach areas.
By identifying moisture issues early, building owners can address problems proactively, minimizing repair costs and preventing further deterioration.
Conclusion
Water ingress remains a significant challenge for buildings of all ages. While older structures are particularly susceptible due to aging materials and injuries to their envelopes, even modern buildings can be affected by poor construction practices, material deterioration, or the effects of weathering. The consequences of unchecked moisture intrusion—including structural decay, health risks, and financial loss—underscore the necessity of proactive detection and thorough maintenance.
Integrating sound building practices with advanced inspection technologies, such as thermal drone surveys, enables property owners to better protect their assets and ensure long-term building resilience and value. Parhelion Aerospace GmbH, a Swiss SORA-approved company, specialises in conducting state-of-the-art thermal infrared drone inspections. For property owners in Switzerland and beyond, partnering with Parhelion can help maintain and enhance the condition of your buildings.
The author is a Swiss BAZL and US FAA licensed commercial drone pilot and CAT 1 Infrared Thermographer, and has the BET Level 1 certification from the Building Envelope Sciences Institute.
Parhelion can help transform your building's future
The Swiss-registered firm Parhelion Aerospace GmbH and the American firm Inspekt AI, working together are able to effectively and efficiently achieve this level of aerial inspections service. Utilizing modern, sophisticated and safe drones, Parhelion captures both visual and thermal infrared imagery of your building. Inspekt AI thereafter employs its proprietary AI program, adept at coordinating thousands of images, to conduct a thorough defects analysis. Inspekt AI then stores the results in a dedicated client-accessible online account that permits owners and managers to examine their building’s condition, and also to monitor it over time if inspections are repeated. This innovative approach guarantees comprehensive and precise results, providing definitive insights that serve as a reliable guide for effective repairs that protect your building and transform its future.
In the same inspection we can also examine your building for energy inefficiencies and greenhouse gas emissions. Energy losses and emissions are signs of a leaky (and unnecessarily expensive) building envelope.
To schedule a modern, 21st-century inspection of your building, feel free to contact Parhelion or Inspekt AI. We are committed to working with you to meet your inspection needs.