Anyone any idea what this is??

[kevin_robson]

We had some damp coming down from our ceiling on our dining room. This seemed to be folowing some old electrical truncing which was non-galvanised. I have now removed the trunking as advised by our plasterer and am about to replaster.

However, he also suggested checking the floor void above to make sure there weren't any leaks. This is what I found. It appears to be attached to the outside brickwork (which looks to be pointed OK etc) and is above where the trunking was. It looks like a white cotton-wool like mould or something? Is it likely the trunking caused this, or this caused the damp to run down the trunking.

http://kjpublic.dynalias.com/IMG_4067.JPG
http://kjpublic.dynalias.com/IMG_4068.JPG
http://kjpublic.dynalias.com/IMG_4069.JPG
http://kjpublic.dynalias.com/IMG_4072.JPG
http://kjpublic.dynalias.com/IMG_4074.JPG

Thanks

 

[noseall]

looks like harmless efflorescence to me.

 

[kevin_robson]

Thanks. The word harmless was news to my ears.
I've done a bit of googling though, and it appears to be a more common problem outside rather than inside, and also states that it needs water in order for this to be created. I also note from the pics I have seen on the web it seems to look like a thin layer, wheras mine is quiet pronounced - as I said it looks lile a fungus almost.

Any idea why this is within the inside of the wall? And does that mean it must be damp, or it possible this hasn't happened as a result of water? I cant see any sign of a pipe that could leak and it looks well pointed?

Also, Would this affect the plaster below it? How do I get rid of it?

Thanks again

 

[kevin_robson]

Found this since my last post. It looks like the 2nd Crystaline type to me.
http://www.aldonchem.com/popup-ab-efflorescence.htm

 

[anobium]

I agree with noseall, it's definitely efflorescence.
The fact that you can see the salts is due to the drying out process which causes the salts within the wall to crystalise.
If the cause of the damp has been corrected all you need to do is simply brush off the salts from the brickwork and replaster.
Sometimes, if the salts have not been removed they can attract moisture back into the wall due to the hygroscopic nature of the salts.