Mold on pressure treated floor joists?
AlexT
| Posted in General Questions on
Hey all – I had a shed delivered to my property that I’m turning into a house. It has pressure treated 2x8s for floor joists, on piers about 1.5-3ft off the ground.
I’m getting ready to put mineral wool and then polyiso boards to insulate the floor, but noticed many of the joists have block spots that look like mold? The moisture reader reads between 10-14% on the joists. Is this a problem to insulate with or how should I approach? It’s been outside for about three months with varying humidity, etc. Thank you!
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Replies
The mold is probably just growing on some surface debris stuck to the joists. You can probably clean that off with a brush and be fine if it's concerning you, just be sure to wear a respirator while doing that. You can get mold killing primer too if you want to ensure no further mold growth, but I don't think it's necassary here.
Bill
Greenhills,
A single bottle of Concrobium will cover all of that.
Thank you Bill and Malcolm, it seemed like it was coming off pretty easily with some vinegar and wiping so thinking it's not too far deep down, but wiping all the joists was a daunting task for the entire floor system, so I did just spray a bottle of Concrobium and hope that does the trick. Thank you!
I doubt the mold is really into the wood to any significant amount. There are various metal salts essentially soaked into the wood during the treatment process that should prevent mold growth within the wood.
Bill
I'm not sure if folks will see this - but just curious, I did a bottle of Concrobium on all the joists and subfloor and then a couple days later a bottle of RMR 86 to try and remove any potential staining so I can inspect things in the future better and make sure no growth is reappearing. But there is no visible change at all unless I scrub or wipe.
It's a lot of surface area to cover, but I'd like to minimize the staining, as well as end with a layer of Concrobium which is supposed to inhibit future growth. Any issue with using a brush or something to gently wipe away the stains (maybe with just white vinegar) or do I need to worry about that cross contaminating. It would be a lot to do in disposal wipes. After I wipe them down, I would do one final spray of Concrobium before installing the batts and foam boards.
It's possible to kill the mold but still see the stains on the wood left behind by the mold (and possibly also by the cleaner). White vinegar can kill mold, so can bleach, and so can the purpose-made mold killing cleaners.
If you're really concerned, Zinsser makes a mold killing primer that you can paint the joists with, but then they'll be white. I'm not sure if you can get that particular primer tinted. I have used this primer before, and it does prevent future mold growth. It can also be applied right over existing mold. Works great, but it will change the look of the wood if that matters to you.
Bill