I am renting an apartment and the tenants recently complained about water droplets on the ceiling in one of the rooms. The apartment is on the first floor and surrounded by plants (we live in a tropical climate), and there is no history of water infiltration before. There are two other floors in the building, and neither apartment presents any water problems. The new tenants painted the whole apartment with Lanco Urethanizer, and since then the problem has appeared. We are currently in the middle of the rain season and hurricane season, but other than that, I have no idea what could cause this. The apartment is built with concrete blocks.

  • do you mean "roof" or the "ceiling" of the room? Also is this the stuff (direct link to PDF) they painted the apartment with?
    – Mike Perry
    Commented Aug 6, 2011 at 3:51
  • @Mike, yes, that's the stuff...and I meant ceiling, I was in the middle of a conversation and translating in real-time when I wrote the question. Sorry!
    – rdrgrtz
    Commented Aug 6, 2011 at 21:54

1 Answer 1


According to the Technical Data Sheet for Lanco Urethanizer (direct link to PDF), or at least from the way I'm reading it, "Lanco Urethanizer" is meant for external applications where you need to make a surface waterproof.

Therefore if those tenants have used it internally to paint walls & ceilings, they have sealed those services ie Made them waterproof.

If I have the above correct, I believe that would explain why you're seeing condensation on the ceiling (and probably on the walls, especially higher up the walls) ie Moisture in the room can't penetrate the waterproof surfaces, instead it just sits on the surface as condensation.

  • Thanks @Mike, I'll consult with the tenants to confirm and mark correct this weekend.
    – rdrgrtz
    Commented Aug 9, 2011 at 15:01
  • Hi @Mike! Sorry for the delay...I can confirm your answer. Thanks for all your help!
    – rdrgrtz
    Commented Aug 21, 2011 at 19:10
  • @rdrgrtz, no worries... Do you have a plan on how you're going to resolve the problem they have created?
    – Mike Perry
    Commented Aug 22, 2011 at 18:19

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