question about mold on wood subfloor

Hi;
I am doing a tile project - installing ceramic tile over an area that was originally carpeted. It is in a bathroom, on a second floor.
Under the carpet there is the wood subfloor. I planned on just removing the carpet and pad, installing backer board, then tile.
When I pulled up the carpet right along the shower, there is black mold on the wood subfloor. I'm pretty sure it's not a leak, just the shower usage and dripping when the shower door opens. There is maybe a square foot area with this issue.
The wood seems OK structurally, it doesn't look rotted out at least and seems to just be mold on the surface.
Is there anything I can or should do to clean it up? Can I bleach it? Seems like putting any liquids or cleaners on wood is not a good idea. Maybe put a layer of the Killz primer on it?
Cutting out the section and replacing is probably not feasible, at least not for me to do, I'd have to go get a contractor for that I guess. The whole shower would have to be removed I think.
Thanks for any information.
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snipped-for-privacy@aol.com wrote:

the wood. I would brush on a mix of water/bleach, not too strong, wipe, rinse quickly, wipe, let dry, and proceed. I would not let the bleach stand for long or soak into the wood, as it probably, over time,would cause some deterioration. Since the wood is sound, the amount of leakage has probably been minimal.
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Bleach wont hurt sound wood, it evaporates to salt, I would pour it on and let it soak and dry by itself, it will just kill anything in the wood.
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Not mentioned by others but be sure it's not going to be too heavy. Some tile types are quite heavy. I'd tend to the vinyl tiles in a 2nd floor. You can find out for sure with a structural engineer but they are pretty pricy.

Is the wood firm as the rest? Not soft in spots? Then you are probably right and it can be covered after treating.

Bleach will be fine if the wood isnt rotted. Use a spray bottle with 50% bleach and 50% water, wipe up well, and reapply. Actually pouring it may not be a good idea if you dont have a tight water seal against the wood and wall (or might be shower it seems). You dont want it dripping down through that to whwatever it may hit underneath.

As long as the wood is ok, just stained, you should be alright. Seriously though, careful on the weight of the tiles. You didnt mention how big the room is or the floor joisting, only a shower which to me seems to indicate an added bathroom in an older house. If it wasnt built to handle the weight of a full tub, it may not take well to ceramic tile either without reinforcement. Vinyl tiles will not be a problem at all.
Looked at an old house once, Mom was thinking to refinish. We backed out before signing once we checked that aspect out. They'd added a 3rd floor bathroom and then tried to tile it and put in a tub. They overloaded the weight bearing and you could see cracks that had developed in the ceiling and walls below it. It was the upper limit of our finances to get that one and a really big job, but we could have fixed it (had structural engineer look, hadnt been edited for the bathroom long and the damage was mostly cosmetic at that stage but would not remain so). The fix would have been to remove the tile and tub and put in a smaller pedestal sink and a plastic type shower enclosure (then replace some 19 sheets of drywall).
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Thanks very much for the responses.
I was also thinking that the spray bottle idea would be best, to just allow the bleach to touch the mold, kill it hopefully, and to avoid soaking the wood with it.
Thanks for the comment on the weight concern.
The house is actually a newer home, built around 2000. There is also a bathtub, but that is separate from the shower and there is no water damage at the tub because we hardly ever use it. Thats why I did not mention it.
I have read a lot in the research I have done in preparing for this project about checking the floor joist spacing, subfloor specs, and deflection; I do have pictures from when our house was being built showing the joists and framing and everything, but Im not sure I can tell what the spacing is from them. However, I do note that the builder was installing tile in the bathrooms, upstairs and down, as well as marble and granite floors, countertops, shower enclosures, etc these were all upgrades.
We just went with the basic and didnt upgrade anything, because the options were outrageously priced and we had already seen the sh*t work that the contractor and subs were doing we decided that if we had to have the upgrades we would do them ourselves later. But there is also something to be said for just getting it built the way you want it.
Anyway, so I havent worried too much about the additional weight since a lot of the homes were built with these heavier materials on the seconds floors by the builder. But maybe Ill go ahead and check into it to be a little more sure, I forgot that the builder was pretty much a bunch of crooks. Ha ha.
Thanks again.
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