The stain was on the ceiling. The problem — was not.
This is one of the most common situations we see. The owner sees moisture, stains, sometimes drops — and logically thinks the problem is where they notice it. But water does not work logically. It works by gravity and along the path of least resistance.
In this case the source was one floor above. The balcony parapet was letting water through — via the joint between it and the slab, water was entering the structure, travelling between the layers, and coming out below, in someone else's home, as a stain on someone else's ceiling.
Without diagnosis this would never have been understood. Ceiling waterproofing alone — pointless. Paint alone — only concealment. The only solution is where the water enters.
We injected the slab at the level where the water was travelling. The material expands under pressure, fills every capillary channel, and seals the path permanently. The owner upstairs — did not know we were working. The owner downstairs — no longer looks at the ceiling with fear.
The problem was solved where it lived. Not where it showed itself.
