Black spot on lumber

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Old 01-31-14, 10:10 PM
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Black spot on lumber

Hi we just built a northern spruce panabode and we are just getting to the lock up stage but noticing most of the interior and exterior have black spots everywhere the wood was wet for extended period of time it does not wipe off or wash off is this bluestain?Name:  IMG_20140119_160716.jpg
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Old 02-01-14, 05:31 AM
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Washing the wood with a bleach/water solution [never stronger than 50%!!] will remove any mildew and often lightens up wood that has greyed from exposure to the elements. Be sure to rinse well.
 
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Old 02-01-14, 07:30 AM
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Is that western red cedar? Or you said it's northern spruce, right? Was it freshly cut and dried? I would say that it looks like it was not kiln dried and had too high of a moisture content before being painted. What kind of paint and primer? Like cedar, I probably would have suggested an oil based primer to lock in any tanins and saps.
 
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Old 02-01-14, 07:39 AM
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Hi it was a kit and the factory says it was all kiln dried, the company building it left it uncovered for the majority of 3 months on the westcoast of vancouver island in BC we get alot of rain and damp weather, the house is just getting to lock up and has not been stained or sealed so this is raw wood, Im just having a hard time making sure it is blustain so far nothing has worked on lighting the colour so thats what im guessing it is, more and more is appearing all the time inside and outside the home
 
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Old 02-01-14, 09:11 AM
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It's mildew, not blue stain.
 
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Old 02-01-14, 10:01 AM
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Thats what I was afraid of thanks any ideas the best way to get rid of it?
 
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Old 02-01-14, 11:42 AM
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Hire a professional remediator and back charge your contractor for leaving your house open.
 
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Old 02-01-14, 11:56 AM
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Oh, now that I look closer, I see that it isn't painted. Duh. LOL

I think it probably is blue stain, as much of the trees that are being milled anymore do have a high percentage of blue stain. While blue stain is a fungus, it is not the same kind of fungus that can be remediated, that can be washed off, or that is hazardous or damaging. It is actually in the wood cells... does not each the cell wall structure, will not spread. See http://csfs.colostate.edu/cowood/lib...ained_wood.pdf

Compare this picture: Timber Stains

A simple way to test might be to take a clean cotton rag, put some alcohol on it and rub the wood. If the blue comes off, it's probably mildew from sitting in the rain. If it doesn't it's probably blue stain from beetle infestation.
 
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Old 02-01-14, 12:22 PM
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ok ill give that a try, the house came from norway the wood was unblemished when we started but after three months of damp and wet its appearing
 
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Old 02-01-14, 12:42 PM
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the wood was unblemished when we started but after three months of damp and wet its appearing
Blue stain occurs while the tree is growing. What you have is mold/mildew.
 
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Old 02-01-14, 12:45 PM
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ya and this is grey to black small dots that make up larger stains, will this keep spreading once dried or do i need to try and treat it?
 
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Old 02-01-14, 02:14 PM
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Oh, it appeared since then? Okay. If the moisture content of the wood stays below 20%, it will not spread.
 
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Old 02-01-14, 02:24 PM
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ok good to know it wont spread once its dry now just to try and get reid of the stain where I cant hide it
 
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Old 02-01-14, 03:00 PM
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I don't know anything about blue stain but if it's mildew, a bleach/water solution will both kill and remove the mildew. We have to wash mildew off prior to exterior repaints all the time here in the southeast.
 
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