Would anyone care to venture an opinion about which of the materials (if any) listed in http://www.chemisol.com/argp.htm would be most suitable for applying a waterproofing coat to interior walls? The description of these products is not very explicit about this. The room whose walls are to be coated is a bathroom.

The ACC-30 page explicitly mentions bathrooms.

EDIT: Ecnerwal makes the good point that waterproofing an interior wall does not make much sense. So, I guess a followup question (should I make this a separate one) is whether any special coating/treatment is necessary, or should one simply paint the interior walls?

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    Waterproofing the inside surface of a wall is generally ineffective - the pressure tends to pop any waterproofing film off the wall, and it eventually leaks. Waterproofing the outside is far more effective (also more difficult to do, but it works much better.)
    – Ecnerwal
    Oct 13, 2014 at 15:45
  • @Ecnerwal that's a helpful tip, thanks. And I agree - it makes sense. Feel free to add an answer if you wish."Don't do it" is also a valid answer. Who else agrees with this? Oct 13, 2014 at 15:48

1 Answer 1


A bathroom should have water resistant materials in the places likely to be splashed with water. Stanard drywall is not used in those locations, but rather hardboard or cement board should have been used. If the proper materials were used in the first place, then you can just prime and paint over them.

What @Ecnerwal is saying in his comment applies more to a situation like basement wall waterproofing. In @Faheem's situation, the water would be coming from the interior, so it would not cause the waterproofing to peel. However, in a properly constructed bathroom, no additional waterproofing coating is required. You may wish to use a "kitchen and bath" paint, but beyond that there's nothing more needed.

  • "the water would be coming from the interior". No, this is Bombay, India. We get periodic seasonal heavy rains (called the monsoon), and so water coming in from outside (through the walls or ceiling) is a significant concern. Oct 14, 2014 at 20:46
  • In that case, interior waterproofing is not likely to help. As @Ecnerwal said, the waterproofing will eventually bubble and separate from the surface. For the waterproofing to last, it must be done from the exterior. Unfortunately, I do not know of an easy way to accomplish that.
    – rjbergen
    Oct 14, 2014 at 20:51
  • Agreed, the main waterproofing needs to be on the outside. I don't think this is a problem per se, just more expensive. Also, it's hard to know how much work needs to be done on the exterior, and where. I've no idea if the bathroom was "properly constructed", but since this is India, I'm guessing not. However, I'm reasonably sure that the plaster damage in that room (which is quite extensive) was caused by leaking from the exterior, as opposed to damage caused by moisture from the interior. Oct 14, 2014 at 21:10

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