WYSK reader Annette wrote in with a question about window sealing. “I live with my sister and brother-in-law. He insists he is in charge of house maintenance, but has never bothered to caulk/seal the window of the room I’m in, and it constantly smells like damp plywood, I assume from the inside of the window frame.” So Annette took matters into her own hands and “taped over the gap between window and frame.” But then the house was pressure washed for painting and “tons of water came in from the top of the window.” Now her brother-in-law is “finally convinced to caulk it” but before he does Annette wants to know if all that moisture, which has built up over years, will cause mold or rot inside the window frame and “what can be done to fix it?”
NV: Hi Annette! You’re absolutely right to be concerned about mold and rot. Mold loves dark places and needs two things to grow–water and a food source, like wood.
Based on what you’ve described, especially that odor you mention, there’s a chance that mold could be getting real cozy in your walls. But without knowing how extensive and far reaching the water damage actually is in your case, here are some basic guidelines you can follow.
The interior of the wall must be dried out before sealing the window frame. Because it’s an exterior wall, this means drying out the insulation as well.
For a minor moisture issue I’d access the interior of the wall with the following steps:
- Pry off any floor molding under the window, then cut openings in the drywall near the floor, between the studs to allow ventilation. If your window has molding around it, remove that too.
- Run a fan and dehumidifier until the wall dries out. How to know when it’s dry? There’s the sniff test for a basic idea, but for around $40 you can buy a non-invasive moisture meter with different settings for drywall, wood, etc. Compare the window wall moisture level with other exterior walls of the house.
- Once the interior wall has dried out (the moisture level reading will be about the same as the other exterior walls), seal the window frame with the caulking you mention. Know that exterior caulking must be designed for exterior use and be waterproof, of course.
- If there’s visible water damage or mold growth on the drywall surface, that section will need to be cut out and replaced. Once the wall is opened, mold can be washed away–a bleach solution is customary, but one could use industrial vinegar or a tea tree oil wash. Of course all must be dried out before the new drywall patch would go up.
Generally speaking, mold clean up at any level should be approached with caution. Wear a mask/respirator with an N95 designation, gloves, and clothing that can be washed in hot water.
Again, not knowing how much of a mold problem you might have, it’s hard for me to be specific, but if you think the water amount in the walls is pervasive, I’d call in pros.
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