We've been full-timing for two months now and dealing with lots of rain in Arizona. I discovered wet carpet around the passenger seat area that has a musty smell. The dampness is directly below our sliding window, and I can see some wallboard swelling at the bottom right corner of the window frame. What's puzzling me is that the exterior window seals look fine, and there's no visible water damage on the inside wall surface. Could this be water running down inside the window frame itself? I'm wondering if blocked window drains could cause this issue. We're on a tight budget - is this something I can tackle myself by re-caulking, or do I need professional help? I'd rather avoid dealer costs if possible.
Window leaks often occur due to failed exterior seals, blocked weep drains, or interior condensation issues. Most can be DIY repaired with proper sealants and tools, but structural damage may require professional assessment.
Water intrusion at RV windows can be frustratingly elusive, especially when the obvious culprits don't seem to be the problem. Your situation - wet carpet with no visible interior wall damage - actually points to several specific failure modes that are quite common in motorhomes.
The swelling wallboard you've noticed is a clear indicator that water has been present for some time, even if the leak seems recent. This type of damage suggests the water is following a hidden path, likely within the window frame assembly itself.
Even when exterior seals appear intact, they can fail in ways that aren't immediately visible. The sealant may have separated from the frame or developed hairline cracks that only become apparent under water pressure. Temperature cycling and UV exposure gradually break down even high-quality sealants.
Many RV sliding windows incorporate weep drains designed to channel moisture that enters the frame back to the exterior. When these become clogged with debris, dirt, or old sealant, water accumulates inside the frame and eventually finds its way into your living space. This matches your description of water seeming to run down inside the window frame.
The window frame itself may have settling or separation issues where it meets the RV wall. This can create a hidden cavity where water collects before eventually seeping into your interior space.
Before jumping into repairs, you'll want to pinpoint the exact entry point. Start by checking the weep drain holes, typically located at the bottom of the exterior window frame. Use a small wire or compressed air to clear any blockages.
Next, perform a controlled water test using a garden hose on low pressure. Have someone inside monitoring for leaks while you systematically wet different areas of the window perimeter. Focus on the top and sides first, as gravity will carry water down to where you're seeing the damage.
Check the structural integrity of the surrounding wall area, as settling or movement can compromise even properly installed windows.
For most window resealing jobs, you'll need a caulk gun, putty knife, cleaning solvents, and appropriate RV sealants. Choose a high-quality polyurethane or butyl rubber sealant rated for RV applications (verify compatibility with your specific window manufacturer) - avoid household caulks that won't flex with road vibration.
Remove all old sealant completely using a putty knife and cleaning solvent. This is critical - new sealant won't adhere properly over deteriorated material. Clean all surfaces with alcohol to ensure good adhesion.
Apply new sealant in a continuous bead, ensuring complete coverage around the entire window perimeter. Pay special attention to corners where multiple surfaces meet. Smooth the sealant with a tool or finger to eliminate air pockets.
For weep drain maintenance, ensure all drain holes are clear and properly positioned to direct water away from the RV body.
The wallboard swelling you've observed needs attention beyond just stopping the leak. Depending on the extent of moisture penetration, you may need to remove and replace damaged sections to prevent mold growth.
Allow the area to dry completely before making cosmetic repairs. Use fans and dehumidifiers to accelerate the process, and monitor for any signs of mold development during the drying period.
If your water test reveals that the window frame itself is compromised or improperly installed, this typically requires professional attention. Removing and reinstalling RV windows involves structural considerations and weatherproofing expertise that can be costly to get wrong.
Similarly, if you discover extensive interior damage or signs of structural issues in the wall framing, professional assessment is worthwhile to avoid more expensive problems down the road.
Regular inspection and maintenance of window seals should be part of your routine RV care. Check seals every few months and reseal as needed - it's much easier than dealing with water damage. Keep weep drains clear and monitor for any changes in how water behaves around your windows during rain.
Consider the age and condition of your windows when planning maintenance budgets. Older windows may benefit from complete resealing even if not currently leaking, as prevention is always more cost-effective than repair.
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