View Full Version : Nail/screw spots

05-01-2003, 11:11 AM
I own an apratment building where one of the apartments has dark spots where the drywall was fastened. The building inspector says its mold but the 50/50 mix of water and clorox I have used in the past will not remove it. I think its residue from burning incense or candles as it looks like what you would see in a building after a fire (but on a smaller scale). I used a common house hold cleaner and it will clean up with some effort. Could this be residue from candles and why would it collect only where the fasteners are located?

John McElwee
05-01-2003, 05:49 PM
Yes it could be residue from candles, cigaretts and even cooking. Are the affected walls outside walls?
The screws or nails conduct heat out of the wall more readily than the field and so a bit of moisture condenses on those points and takes a little bit of the particulate matter in the air with it. After many cycles of this is shows. If it is also on the inside walls I can't explain it.

Jeff B
05-08-2003, 11:19 PM
I don't know if this applies, but there was a similar discussion on the building science forum a few days ago...

Building Science Forum (http://www.jlconline.com/cgi-bin/jlconline.storefront/3ebb2bbb000a4609271a401e1d2905b1/Catalog/1135?read=8778)

Myron Ferguson
05-26-2003, 07:01 PM
I have seen ceiling joists highlighted in this way also. I think it is because of heat conduction also.