Where is this wall water damage coming from?

Question

It was raining today. At evening, I notice something's wrong on the wall. Is it a re-pointing issue?

The partially damaged wall is only under the windows. I accidentally leave the window open and by the time I fond it, there were some rain on the window wood frame. The room feels extremely humid. I looked out on the brick wall, the pointing seems fine. If the leak starts from the roof, would the wall above the window also be damaged as well? We just replaced the roof couple days ago. However, there's a missing medal that the roofer hasn't installed yet.

Answer 1

What happened to the wall?

Water has penetrated the structure of the wall and is emerging behind the paint, forcing it off. There may also be efflorescence, depending on the material the wall is constructed from.

Is it a re-pointing issue?

Probably not.

The surface of the wall is uneven overall, this might be a sign that this problem has occurred before.

If the problem recurs after fixing all the other possible causes, I would then consider re-pointing the exterior of the wall (presumably a brick wall) and/or applying a water repellent intended for that purpose & material.

I accidentally [left] the window open and by the time I [found] it, there [was] some rain on the [window's] wood frame.

This is probably the cause. Water penetrated past the window sill. You may be able to make the area more water resistant but the best way to prevent a recurrence is to keep the window shut when it is raining.

We just replaced the roof [a] couple [of] days ago

Then that could also be a suspect, I'd check the wall structure above the window for high humidity (you can get humidity testers for walls). If the underside of the new roof is accessible, I'd also inspect that for signs of water penetration.

there's a missing medal(sic) that the roofer hasn't installed yet

Depending what this is (flashing?, guttering?), it's absence could have contributed to the problem.

Answer 2

It appears to be a leak - where the leak is could be anywhere from near the damage (but it's usually not) to the roof, and it may not be directly above, depending on the path the water is taking. While I suppose it could be repointing in a brick or stone wall, I'd probably start looking at the roof, unless looking at the outside of the building while it was raining indicated something obvious lower down (a broken or clogged gutter spraying water on the wall, for an example.)