Landlord not fixing water leak

[mother]

I am SO frustrated, and I'm hoping someone could offer good advice on how to deal with this problem.

I moved my business into new premises on the 1st of July. And when I say new, I also mean the building was brand new. When I first looked at the premises, I saw (what looked like) old water damage; just a few dry bubbles in the paint. The landlord explained that this was as a result of rains they had before they completed the building. At the time, the explaination seemed feasible, since there's a back door and toilet window where the rain could have blown in. Now I know he was lying.

Within the first 2 weeks of us being there, it became very clear that the water damage was as a result of a leak somewhere upstairs. There is a load bearing column in the corner of our toilet (two sides in our toilet, and two sides in our shop) where water runs down continuously. I don't mean the wall is damp, I mean tiny streams of water run down all 4 sides of this column. And since our toilet is right below 8 stories of bathrooms, I can only assume that there is a plumbing problem in one (or more) of the bathrooms above us. For the life of me, I have never seen water running down through a slab (the ceiling) and down the wall. You can obviously imagine how we battle with mould in our shop, since this wall is wet, permanently.

This is a photo of the column inside the toilet:


This is a photo of 2cm long mould growing on the outside of this column (in our kitchenette area):


And this photo shows how wet the outside of the column (in the shop) is. Where the dark yellow streaks are, the paint is actually "wet" again... if you touch it, you actually get yellow paint on your fingers:


Last month I told him I feel it's only fair that I do NOT pay him the full rent, until he fixes the water leak. And he agreed. He then told me there is a problem with one of the toilets somewhere above us, and he will fix it immediately. It is a month later, and the water is STILL running down the wall.

Should I worry that, over time, a leak like this could cause structural damage?

Can I report this problem to an authority that would force my landlord to fix this leak?