Mysterious wet spot on wood floors

A wet spot appears in the middle of my wood floor whenever it rains. I've recently replaced the roof but the spot continues.
Yesterday, my chimney guy went under the crawlspace and said that the spot is mold that "activates" whenever it rains due to the humidity and I need to rip out the entire hardwood and subfloor. He wasn't trying to sell me this service as he doesn't do this.
Is it possible that the mold would "activate" and look wet due to humidity? The chimney guy said that there are no "trails" leading to the wet spot and that there is nothing wetting the floor from the underside. This is an old 1870's house that I just purchased. He said that the floor must have been saturated a long time ago and the mold started at that time. He said that the mold is in small areas and looks white and fluffy kinda like the freezer burn you see on ice cream that stays in the freezer too long.
Any help would be appreciated as I prepare to remove all of the the floor.
Thanks, Gus
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gus wrote:

Well some things jump to mind: 1) check under the crawl space when this wet spot happens. Run a cord under theere NOW while it's dry (unplugged). Also, you might hit your generic store for a UV light, I don't know about house molds, but I recall taht a bunch of molds that you can't easily see in regular incandescent, light up under UV. $6 at the overpriced hardware store and you can use it for your spiderman poster later ;)
2) get a second opinion on ANYTHING that might cost you $THOUSANDS.
3) nothing will prevent that from coming back, if it's there. The spores are there. ventilation and fungicides are appropriate to kill the mold.
4) get another opinion on the cause and the solution.
if it's there, like he says, then you should SEE IT YOURSELF.
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gus wrote:

A wet spot is not the same as mold or mildew. A puddle? Check the roof, especially if there is a wet spot or stain on the ceiling above, or a dripping light fixture above the puddle. We helped a friend with a leaky roof - the actual leak was warped deck on roof with a loose shingle on it. The water dripped onto a rafter and followed the rafter to the center of a bedroom, running down via the ceiling light fixture in the center of the room.

If the crawlspace is too wet, it needs to be assessed for drainage, waterproofing and ventillation. The "chimney guy" is not the guy to do it.

If the underside of the floor is rotted/moldy, and you have new flooring, you have a seller who concealed a problem. Wet subfloor should be causing older flooring to warp or show other signs of dampness.

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Spray it with bleach from the crawlspace, Does crawlspace have plastic on the floor, is it vented, is the dirt graded and gutters clean , is it dry.
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snipped-for-privacy@webtv.net (m Ransley) wrote in message

all great comments...thanks all
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