Waterproofing of all wet areas in a building is essential, not a luxury to avoid. Several concrete buildings built without doing so in the past are having to undergo maintenance work now. Also ensure all plumbing works including any concealed wall pipes are capable of handling appropriate water pressure and checked for leaks before concealing. There are several methods to waterproof wet areas such as waterproofing membranes and/or under tile applications. Do remember all standard ceramic tiles as well as concrete is porous, not 100% waterproof.

For solid surface showers, moisture resistant plywood, moisture resistant gypsum board, or cement backer board are recommended. Cement backer board is often preferred due to its durability and moisture resistance. Finishing typically includes making sure seams, especially corners and joints, are properly sealed with a waterproof membrane. This prevents water infiltration and ensures a stable base for solid surface installations, maintaining the integrity and performance of the shower wall over time.

Its all about there experince & knowledge .... if civil contractor has dealth with that kind of issue u r facing they can provide solution. for Dr. fixit team m not sure but you have to place request in company.

You need to address the problem at the source of the dampness. This is most important. And it will work out to be comparatively inexpensive as it will eliminate the need for tiles and repainting from time to time. Rest of the solutions are only temporary and decorative in nature as the source problem will be of a continuing nature damaging the structure in the long run. Tiles have their own place and do not look good in all places. Once this leakage problem is addressed, ₹ 3-5 Lacs seems to be a very good budget to take care of all internal and external painting needs.