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Strange black stuff coming out of my fiber cement siding

Strange black stuff coming out of my fiber cement siding

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  #1  
Old 11-29-07, 09:13 PM
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Strange black stuff coming out of my fiber cement siding

My home was built in 2005. In the summer of 2006, a tar like substance started appearing on the fiber cement siding in the east side of the house. Then, in the summer of 2007, this tar like substance also started appearing on the south side of the house. What could be causing this? Is this something for me to be concerned about?

here's a picture of the east side http://i231.photobucket.com/albums/e...2/IMG_2527.jpg

close up picture http://i231.photobucket.com/albums/e...2/IMG_2523.jpg

south side picture http://i231.photobucket.com/albums/e...2/IMG_2526.jpg

Thanks in advance.
 
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  #2  
Old 11-30-07, 05:18 AM
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Black Substance

Is the location of this problem always under a window? It could be coming from the weather stripping used around the windows.
 
  #3  
Old 11-30-07, 05:23 AM
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It's likely coming from the butyl flashing tape that was likely installed over the nailing flanges of the window. It must be getting so hot under there that it's melting in the summer time. I've never seen this. I'd be curious to know what brand of flashing tape that is so that I could avoid using it! I wouldn't think that someone would have used roofing cement under there, but that's a possbility too, I suppose.

Best thing I could say to do would be to try to scrape off what you can with a razor blade, then remove the rest of the tar with an adhesive remover or lacquer thinner, then perhaps run a small bead of siliconized acrylic latex caulk along the bottom edge of the siding. Just caulk a small area several feet long in each spot where the tar has been showing up to act as a "dam" to prevent it from leaking out again. You'll likely need to repaint the siding once the tar has been removed because the solvents will also remove your paint.
 
  #4  
Old 11-30-07, 09:02 PM
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Thanks all for the reply. To Wirepuller38, yes, it seems that it's always happening under the window. To Xsleeper, I don't know what kind of flashing tape the builder's subcontractor used. But if it's the flashing tape melting, is that something I should be concerned of in terms of my window eventually loosing weather protection? I tried to wipe it off once and it felt a little greasy.

Thanks again.
 

Last edited by canon2; 11-30-07 at 09:44 PM.
  #5  
Old 12-01-07, 06:40 AM
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I don't think that it would exactly be like a popsickle melting, leaving a void behind. The butyl is usually about 1/16" thick, with a plastic or foil facing. I'd be quite certain that if it is melting, that there is a sticky mess and that the facing is completely sealed to everything in sight. If anything, I would guess that your windows are a little too sealed. What you are seeing must be the "excess" melting and dripping off. Of course it's possible that years and years of this same phenomenon would affect the seal, possibly making it crisp and dry to the point that it would no longer be sticky would want to crumble off like a potato chip. Hard to tell. By that time, you'll be replacing your trim and siding anyway and can reflash the windows.
 
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Old 12-01-07, 01:05 PM
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Must be the butyl. It should have been behind the metal flashing.
 
  #7  
Old 12-01-07, 08:32 PM
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Thank you for all the replies.

Arlene
 
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