Mold on exterior sheeting that has been exposed for 6 years

We just purchased a cabin that is just framed in and the outer sheeting (pressboard plywood) is on. The roof is on and there are overhangs which has helped protect some of the wood. It has been exposed to the elements as is for 6 years. Some of it has turned a little black, as wood does exposed with no finish on it, but the wood is strong and not flaking or rotted. It is out in the open so well exposed to winter snow and summer sun. We need to decide if we should replace the sheeting before putting the siding on. We have had several opinions - keep it and replace it and now we don't know what to do. A builder said there is so much glue in the sheeting that if it is mold it would not have penetrated it. Not sure I believe that.
I am allergic to mold. Because of this we are wondering what we should do? Some have said scrub with bleach, some have said replace. I also thought of power washing, but was told this would tear the pressboard apart. I thought of sandblasting with a home sand blaster I saw for removing paint, thinking this may be able to be adjusted. Just looking for opinions and ideas. Also thought of painting it to seal it. Is this a bad idea? Does it need to breathe?
The cabin has half log pine siding waiting to be installed over the sheeting. We plan to use Tyvek under it. Although I just don't want to take a chance with mold, we would also like to avoid the labor and expense of tearing off all the exterior walls and replacing them. We are torn as to what to do. The interior will have insulation, drywall and probably some sort of wood paneling or planking for the walls. We want it well insulated against the winter weather and summer heat. The cabin is in an area where it is exposed to heavy snow and very cold temperatures in the winter, as well as sand and hot and sometimes humid in the summer.
Any thoughts welcome...
Thank you
Autumn
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Please, please, please don't fall into the "scare story" syndrome. There will be some here that will quickly jump into that category.
I deal with these issues professionally and I am fairly well read on the issues. Please do not take my word for it, and don't take the word of alarmists. There are many sources for good technical information, but this one is especially good and comes from a fairly believable source: http://www.epa.gov/mold/i-e-r.html#Remediation Please read the entire article.
Mold exists. Mold has always existed. Mold will continue to exist. It is in the air all around you and on everything you touch. Maybe the boy ( A John Travolta movie) that lived in the special bio tent was free of mold, but the rest of aren't.
Mold can become a problem for humans when it is actively growing.
Black stains on exterior wood exposed to the sun is exactly that - black stains. It may be rust from nails, some may have been caused by mold, or other discoloration.
Bleach kills mold and there are commercial mildewcides/biocides. It is not typically considered productive to kill mold. Any mold that you kill with bleach, etc will be replaced by new mold. Mold can only grow if it has food, water, proper temperature, and dark (hidden from UV). If you remove any of these, especially the water/humidity source, the mold can't grow. It is still there in a dormant condition, but not actively growing.
The builder was telling you that the way wafer board and other man-made sheathings are made is to saturate the chips, dust, by product or whatever with resin and press and cook them into sheets. Is it 100% mold free?, probably not. There are some newer exterior sheets and drywall that are impregnated with borates and/or other mildewcides or biocides.
If this thing is exposed to the sun and the walls are dried out, I wouldn't pull it off. If you would feel better spraying everything down with bleach or other biocide, do so. Please read the EPA or other technical source information and make intelligent decisions. Don't knee jerk to scare mongers.
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Autumn wrote:

I wouldn't be all that concerned with mold. I would be much more concerned about the structural integrity of sheathing that has had 6 years of exposure to the elements. As long as it is truly sound structurally, I would go ahead and apply the log siding. However, I probably would spray the outside with some wood bleach just to clean things up and spray it off with a hose. You can use a pressure washer if no hose is available, but use a wide pattern and stay a couple of feet away from the wood as you spray. You want to rinse off the bleach and dirt, not blast off the wood itself.
Matt
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Autumn wrote:

I clean mold/mildew/whatever else accumulates on my house trim every spring with a product called JOMAX. It's about $18-$19/gallon at Lowe's, ACE, H.D. 1 part JOMAX to 5 parts bleach & 20 parts water .. .. spray it on with a pump-up garden sprayer, and watch it disappear !! !! !! I'd be willing to bet the stuff on your siding would respond favorably to this treatment, and it certainly can't hurt to kill off anything parasitic before burying it in your walls. Very fast & easy to mix up and apply .. why not give it a shot ?? ?? ??
<<<__ Bøb __>>>
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Sounds like the jomax is a ripoff to me. The 1:4 bleach and water will do what you said.
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Steve Barker


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Did a little research. Seems that this so called JOMAX is nothing more than $20 a gallon bleach. Here's the msds. Just as I suspected.
http://www.zinsser.com/pdf/MSDS/jomaxmoldmildewremovermsds.pdf
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The msds is misleading, as it lists the resulting mix after the user adds bleach. There is no bleach in Jomax according to the label on the container. The "active ingredient" in Jomax is "0-Phenylphenol, sodium salt". It's my opinion that Jomax does add to the cleaning capabilities of bleach and allows a lower concentration, hence safer to surrounding shubbery, of bleach to be effective. It is expensive and if not for the shubbery arround my house, I would use a higher concentration of bleach and/or add TSP to the mix.

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Excuse me, I found the MSDS you were referring to. It depends on which "JOMAX" product we are talking about. The one you spoke of is merely vinegar. Another $20 a gallon scam.
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Vinegar is acetic acid http://en.wikipedia.org/wiki/Vinegar The active ingredient in Jomax is a biocide. The two are quite different. At least to some of us.

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It says right on at least two of the MSDS's "acetic acid".
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Steve Barker



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I've got the jug right here in front of me. There's no bleach in it. What are the contents of the jug you have?

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I'm looking at their website. And the official documentation. Not the lying label. The MSDS is the only real way to tell what any product has in it. The labels are always disguised with laymens terms.
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Steve Barker wrote:

Sorry, but I've used bleach & water AND I've used JOMAX+BLEACH+WATER .. .. .. the JOMAX blend is much quicker-acting and thorough without a doubt. Try just a quart of it for yourself and I think you will see there is a difference.
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I have some lumber that came with some green mold. I may just do that.
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Steve Barker


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Watch the weather forecast. Do this when 3 or more days of dry weather is anticipated. Use a powerwasher with bleach added. You don't need extreme pressure. Wait 8 hours. Rinse well. Wait 3 days. Apply your Tyvek or whatever.
If the mold is actually growing on the backside of the sheathing and on the studs, you may have to replace it due to your sensitivities. Pull one sheet off on the worst area you find to find out.

If you were, you would not be breathing now. Maybe more sensitive than the general population is more appropriate?
When I was young, I was overly sensitive to "cedar" pollen during cold weather snaps. Actually is juniper ashe in south central TX. Made me miserable. My body has adjusted to it over the years. Have averted from "allergy" medication.
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Jonny



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Thanks for all the replies. I know we will use one of these. I really feel the wood is strong and hope this cleaning will take care of it.
Autumn

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