The attic terrace leaked for unknown reasons, dripping into the extension of the balcony window down

There must be a flange on the edge of the terrace to keep out the water, and it is generally unlikely that it will flow directly down (the concrete itself is also waterproof). At present, the most likely thing is that the waterproof is broken, and if the waterproof is to be redone, it is generally necessary to do it all at once, and if you just make a piece, the seam is more likely to leak. However, this is a large amount of work, and it is necessary to open all the tiles, and it is likely that the insulation of the roof will also have to be redone.

In fact, if the flange is high enough and the terrace is well drained, I think it is better to directly pave the waterproof, and then pour it with concrete, which is more thorough.

The several phenomena of water leakage you mentioned may be the cause of the final water leakage, so if you want to solve it well, you must deal with these phenomena, otherwise it may not be able to be repaired! Do not do engineering, provide free professional technical consultation on concrete waterproof leakage repair.

First of all, you have to find the leak to be able to get the right treatment.

1. If there are drainage pipes, floor drains, etc., check whether the seal is tight or broken.

2. Before laying bricks, whether the terrace has been waterproofed, like this situation is generally caused by structural leakage, wall corners and floor surface deformation, you use glass glue around the corner of the terrace to see if it can be effective.

It should be that the side of the balcony ceiling drainage pipe is not well sealed, resulting in the water leakage of the balcony upstairs.