It is often said that the biggest enemy to a house is moisture. This adage holds true for window sills, even on interior sills. Moisture can affect a window sill from a variety of sources.
Problem 1: The Leaky Window
The most obvious source of moisture is a leaky window. Window leaks, regardless of where they occur, are likely to end up placing moisture directly on or in the interior sill.
Problem 2: Moisture Buildup Within the Home
Moisture buildup can also occur inside the home itself, even if the window is watertight. Condensation forming on the inside sill is a source of common moisture problems that affects windowsills.
Problem 3: The Outer Sill
The outer sill is far more subject to water problems than the inside. Weather directly affects this portion of the window. Unless you have impermeable or vinyl windowsills, you must ensure that the window is protected from moisture. Moisture can rot, swell, shrink and distort the windowsill. Worse, the sill may allow the water to leak into the frame of the house itself, which is where you start having problems worse than a damaged sill. Ensure that sills are watertight and properly sloped to allow water runoff.
Problem 4: Mold Growth
Although windows are usually immune from mold problems, the sill is the one exception. Mold growth on window surfaces is rarely dangerous (since windows do not typically develop stachybotrys, a toxic mold found in some homes), but it is ugly and just plain gross. Keeping the window clean and moisture-free is the best way to prevent mold from forming.
Problem 5: Broken or Cracked Sill
Finally, the most evident windowsill problems are when the windowsill cracks, breaks or falls off. Thankfully, this level of damage doesn’t mean that you need to replace the entire window, but you should get the sill replaced as soon as possible.
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