Eventually the occasional leak will cause the paint to peel.
Checking the outside of the window, I saw that the side with the leak, has a gap between the casement window frame and the concrete wall. If it's hard to stretch out your head and look, use a hand held mirror to check. Or a camera to take photos. Be careful not to drop the mirror or camera.
Compared with the side with no leaks, there are no gaps - the photo below shows the paint covering the casement frame and concrete wall.
Assuming the gap is the problem, I bought a tube of silicone and gun (about $8) to cover the gap. Before starting:
- Check the weather forecast. I always try to let silicone dry for 24 hours.
- Wipe the surface with a moist rag, I use an expandable old sock with holes, use and throw it away. Let it dry out for a while.
- I used a wooden ice cream stick to try to spread out the silicone.
After application, the problem has ceased. From the photo below showing the uneven silicone application, you can see I'm no craftsman :)
If your casement window is leaking, according to this forum's post, there could be a few other reasons. This other web page has a diagram showing the casement window structure and how the leak might flow. Might be useful.
