Eliminate moisture issues with proven tips to fix leaky window seals. Learn common causes and effective repair methods.

Head of Content, D. Gorenko
Updated June, 5

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Immediate Steps to Stop the Leak
Tools and Materials Needed
Step-by-Step Repair Process
Can a Homeowner Fix It, or Should You Call a Professional?
Who to Call for Professional Help
Safety Warnings and Insurance Tips
Material Degradation and Age
The seals on windows can wear out over time. Sunlight, rain, wind, and temperature shifts break down the flexible materials. Constant exposure to UV rays and harsh weather can cause the sealant to crack, shrink, or lose its grip. This gradual deterioration makes the seal less effective at preventing water from seeping in.
Poor Installation Techniques
If window seals are not installed correctly from the start, gaps or uneven surfaces may occur. Inadequate preparation, misalignment, or the use of low-quality sealants can lead to immediate weaknesses that allow moisture to pass through. Even minor mistakes in installation can create pathways for water to leak during rainstorms or when building moves.
Thermal Movement and Expansion
Windows and their seals continuously expand and contract with temperature changes. Extreme heat or cold forces materials to shift, which can result in cracks or small gaps along the seal. Over time, these repeated movements wear down the integrity of the seal, making it easier for water to pass by.
Faulty Materials or Sealant Products
Using materials that are not designed for the specific conditions of a building can lead to premature seal failure. Not all sealant products are suited for high moisture or extreme temperature variations. When the wrong product is used, it may not bond properly, leading to an earlier breakdown of the seal.
Structural Movement or Settling of the Building
Buildings can shift due to settling over time or due to natural ground movement. This movement can cause stress in the window frames and their seals, breaking the continuity of the barrier against water. If the window frame isn’t securely fixed or if the structure shifts unevenly, the window seals may crack and allow leaks to occur.
Improper Flashing and Surrounding Design Flaws
Sometimes the leak is not directly due to the window seal but because of poor design in the surrounding structure. Improper flashing, inadequate drainage, or design flaws can force water against the window. In such cases, moisture finds its way behind the seals despite them being applied correctly. This issue is common in older buildings or structures that have been modified without proper planning.
Environmental and Moisture Factors
High humidity, heavy rainfall, and ice can overload a window seal. When excessive moisture builds up, it can exploit even the smallest imperfections in the seal. Additionally, if condensation forms inside the window frame, it can further weaken the seal over time.
External Influences and Local Conditions
Certain areas have unique weather patterns that can affect window seal longevity. For instance, buildings in St. Louis and Nashville may experience seasonal extremes that the materials were not designed to handle. Local environmental conditions, such as sudden storms or flooding, can compound the stresses on window seals.
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SERVING
Brentwood, MO
1025 Hanley Industrial
Brentwood, MO 63144
Nashville, TN
45 Willow St.
Nashville, TN 37210

St Louis Location
(314) 664-3011
St Louis Location
1025 Hanley Industrial Brentwood, MO 63144
Nashville Location
(615) 515-3015
Nashville Location
45 Willow St Nashville, TN 37210
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