How to Know Source of Damp Walls in Multi Story Building

One hires a competent leak detection company.

Or, one buys the necessary tools to diagnose the problem you have.

Can't help you from the USA.

This could prove to be a difficult sleuthing process, unless you get lucky.

If you have plumbing drawings, you may be able to find where pipes are near to the moist areas, and look there.

At any moist area, check the next floor up, etc. If the wall changes from moist to dry, this may help to locate the leak. Also check adjacent floor/ceiling areas.

Although leaks will tend to drip downward, it is also possible for moisture to wick upward through porous materials. This may tend to complicate your search.

Check the roof and exterior walls for visible cracks, especially at corners.

Best of luck!

You can try a thermal imager. It will show heat changes, and start you in the right direction. Good luck.

Saw a hole in the wall where it is wet!

Usually, if each floor plan is the same, the drain pipes and water lines will be run up through the building together in an enlarged wall space.

It will usually be about 2 feet square near the kitchen/bathroom if they are near each other. Otherwise there will be two plumbing chases one near the kitchen and one near the bathroom(s).

There will also have to be a vent stack going out through the roof for each chase.

Air Conditioning lines, if present, will run up through the building together to the roof units if that is where they are. If you have wall units these will be lacking.

Most roof leaks show up at the top floor ceiling unless the vent stack or AC line roof goosenecks are leaking. In that case water could run down the AC lines or pipes to any one of the floors.

At each floor is a plumbing clean-out for the waste lines. If someone didn't screw the plug into it after removing the test bulb during construction the screw-in plug could be leaking.

Best way to start is just cut a hole in the drywall where it is wet and see what you've got.

If a drywaller ran a screw into a water line it might take a long while for it to rust through and start leaking. Could be any number of things tho.

Use the same instruments that used to detect the damp wall. Your eyes most probably. What did you notice? Discoloration, flaking paint, puddling? If it is only damp when it rains then search for the point of ingress. If it is always damp then start chiseling holes in the wall and follow the water. If a pipe is leaking, you will find it. If it is damp on the ground floor from the floor up then you may have a rising damp problem which will not be easy to fix. Probably not even worth the effort to ameliorate. Just needs doing.

Many buildings in India have such problems. Concealed plumbing is another headache unless job is done properly. Mostly concealing is done inside the flats externally pipes are exposed. Start with terrace see that parapet wall on the top is covered with "Cudppaha" stone as leakage goes down from there. If building is very old it will need 2 coats of silicone based weatherproof chemical. Over this you have to give 2 coats of 100% weather proof exterior paint of reputed make. This may solve the problem to some extend.

For an excellent source of information on dampness in buildings and how to solve them, visit www.buildingscience.com.