This is a problem that comes up from time to time, and it's important to know what to do about it. Paralysis often sets in when an upstairs neighbor's apartment is leaking and then they don't want to do anything about the drips heading into your apartment. My own past history includes:
1. Upstairs neighbor when we were in a rental apartment whose new bathroom renovation leaked like crazy, leaving us to discover black mold growing on our ceiling upon our return from a 3-week trip overseas for Christmas. The upstairs neighbor claimed that he "didn't believe" it was leaking and demanded to see. Lucky for us, we were about to move into our own apartment.
2. In our new apartment on the 5th floor of a 5-story building, the 4th floor neighbor had also renovated his bathroom and then tried to blame us when the water started dripping down into the 3rd floor apartment causing extensive damage. We were able to demonstrate to the third-floor neighbor that we don't even have any running water on that entire side of the building (our apartment is and always has been two apartments combined) and then explained to her the 4th floor neighbor's responsibilities.
That said, I'm not the only one who runs across water leak problems. I talked with a Taiwan attorney colleague about the situation in general. In short, he pointed out there are a couple of laws governing the apartment leaking issue:
1. Regulations for Management of Apartment and Building (公寓大廈管理條例) Articles 10 and 12.
2. Civil Code Part II (Obligations): Articles 184 and 191 (torts).
So there are usually three basic scenarios:
(1) For those leaks caused by or the fault of the upstairs neighbor, the neighbor gets stuck with responsibility for the repair work and for the damages to the neighbor, pursuant to Civil Code articles 184, 191 and Regulations Articles 10 paragraph 1 and 12. This is perhaps more easy to establish when it's clear that the upstairs neighbor has made some recent change or that it's somehow their clear fault. Apparently the first scenario applies to any situation where it's clear that the pipes or lack of waterproofing was the responsibility of that neighbor.
(2) For leaks caused merely by facility aging (i.e., the overall age of the building, the floor, pipes that are built into the building for carrying waste out or water in) or natural disasters, the relevant parties (upstair and downstair residence) share the expense pursuant to the Regulations' Article 10. Apparently this second scenario applies to the concept where it's not the upstairs neighbor's negligence or deliberate fault that there is water leaking -- it's just that the building has gotten old and there is a problem affecting the two households. For example, if there is a pipe buried into the floor and because of age and perhaps an earthquake there's now a bit of dripping, then the upstairs and downstairs have to share the cost.
(3) For those leaks causing by the poor maintaince of the apartment building, the management committee of the apartment building should take responsibility pursuant to Civil Code Article 184 and Regulations Article 10 paragraph 2. Apparently what this means is that if the leak is the fault of building infrastructure shared clearly by everyone, then all the apartment owners in the building have to share the responsibility. I once lived in an apartment where one day an exterior wall sprung a leak -- literally a stream of water came out of a pipe that was shallowly buried into the exterior wall shooting out in a big spray. In the weeks before, the leak had apparently been dripping through the concrete and growing mushrooms on the downstairs neighbors' walls. The building came together quickly to resolve it, and I was actually a bit relieved by the publicly visible nature of the leak because some neighbors had privately been grumbling in previous months that the leak was all because I had a bathtub -- one of those Japanese-style wooden things.
Of course for damage to the downstairs neighbor's home, it's important to differentiate between the damage that is the fault of the intial leak and the damage that is caused by the delays from the upstairs neighbor refusing to take on their responsibilities. Thus, in the No. 2 scenario indicated above, if a person were to go to the upstairs neighbor and say that they need to get this checked out by a contractor and the neighbor refuses, then the upstairs neighbor is basically risking that they will be responsible for the giant pools of accumulating poop water, heaps of mold and damaged furnishings down below. However, it is also worth keeping in mind that a downstairs neighbor who is unwilling to accept that there are situations that may require a splitting of costs or which may require the whole building to share expenses could also contribute to the scope of the problem. Perhaps the best way to approach this is to tell upstairs neighbors that regardless of who has to pay for the repair work in the end, the costs go down for everybody if it gets resolved as soon as possible.
Something to watch out for is that if you have a top-floor apartment roof-level leak is that it is the building's management committee that will normally be responsible for collecting the money to make the fix. We had a very slight leak that we found before we moved into our current apartment in an old building, and there would have been a couple of potential fixes that I didn't find palatable:
1) the city will normally allow the erection of a tin roof over building's roof -- I wasn't crazy about that because I wanted a rooftop garden; or
2) the neighbors would likely have approved a scheme that would have only provided a temporary patch to a very aged concrete roof that probably would have involved the cheapest, nastiest tar substance somebody could have found. Given past experience, my guess is that at least one of my neighbors would have decided it would be cheaper to "do it himself" and then demonstrated the tar-painting skill of a Jackson Pollack.
So, ignoring our legal rights and the hassles of trying to force the neighbors to pony up for a rooftop repair, we simply fixed it up in the way we wished to do so. The repair guys even found a potentially dangerous problem that they fixed for us at no additional cost in that the existing section of tin roofing providing shade over about 1/3 of the roof had steel supports that weren't really bolted into anything other than some loose concrete roofing tiles. And we have a 10-year guarantee on the workmanship.
