I pulled up some water damaged particle board underlayment to replace it with plywood and found some damaged subfloor boards. The subfloor is 2x6 T&G which is nailed to some giant beams every 48". some of the subfloor boards appear to be eaten by carpenter ants. Many of them have some white stuff on them and I am not sure it if is some mold or dryrot or if it is just old construction debris from when the house was built about 35 years ago. I think some of the boards with significant damage will have to be replaced, but I do not want to replace all of them if it is not structurally necessary. I think the crawl space has had a lot of water problems in the past but we are having a french drain and sump pump put in which should fix that in the future. I really do not want to pull up any more of the particle board underlayment as it is in serviceable condition in the rest of the house. What do you think, should I just replace the boards that are most damaged, or is this white stuff something to be concerned about?
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