Does anyone have any ideas as to what could be going on with this ceiling?

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  • 2
    Need better context in photos and better description. I don't know what you mean by 'hairy thing.' – M.Mat Feb 19 '17 at 9:54
  • Looks like concrete that has seen moisture. – isherwood Feb 19 '17 at 14:11
  • I also can't make out anything from the pictures, but google 'efflorescence' and let us know if we have a match. – Aloysius Defenestrate Feb 19 '17 at 15:26
  • It looks like lath and plaster to me but as others have mentioned the photo is difficult to make out. In older homes that have wooden slats (lath) covered with a layer of plaster where moisture gets to the area the plaster falls down, I am guessing this is what the photo is. If damp the leak needs to be fixed first and dried out then the plaster can be reapplied, Some people will remove the lath and plaster and install Sheetrock if it is a large area. Some really old turn of the century had horse hair mixed in the plaster for added strength. – Ed Beal Feb 19 '17 at 16:46

Is that a portion of a rebar that is exposed? If so, that is dangerous. That means it and other rebar is improperly installed. Depending on what is above, the floor/ceiling could be overloaded and come falling down. Concrete is designed to fail by tension (cracking from below) rather than fail by compression (exploding under pressure,) but I wouldn't trust it. If one rebar is installed improperly, (installed too close to bottom of slab,) then I'm sure many other rebars are not installed correctly. Obviously it's been failing for some time (note the rust) but if a new load is added, (snow, waterbed, etc.) it could trigger a disaster. Get a professional to look at it immediately.


Efflorescence. It's described, explained, and discussed, ad nauseam, on the internet. efflorescence-cause

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