Mold (?) In Crawl Space

arnheimacres

I have a problem with mold (I assume) forming on the joists and underlayment in the crawl space on a new house construction. Cleaned it once with a soap a couple months ago, but has just started reappearing. Plastic was put down early on and it is dry. I have considered putting a dehumidifier under the house. Anyone out there have this problem before, and if so, how do you get rid of it and stay rid of it? Thanks.

slickshift

It's not that dry if you're getting mold

If it is dry now, the soap didn't kill it and it came back
...and you must kill it
50/50 bleach/water or my favorite X-14 (cleaner) will kill it
I's also consider sealing in the affected parts with shellac (BIN) after killing it

And you must be sure it's staying dry

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arnheimacres

Thanks Slickshift. There is no moisture as far a being able to touch it, but there is humidity. The mold seems to be worse around the vents. Can the bleach/water combination be sprayed on, or must it be rubbed in? Thanks again.

slickshift

You can put it in a spray bottle and spray it on
Usually a good soaking will get it just fine
If it's really into the wood fibers a stiff brush may be needed to work it in
But as it sounds pretty new, it shouldn't be that bad yet

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slickshift

Mmmm... yeah it's got to have food, moisture, and warmth to grow
Raw wood is good food
After you kill it, I'd seal it with BIN if possible (eliminating the food), and do what you can about the moisture

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Top Cat

Mould is sometimes caused by condensation from airconditioning. It's important to seal between areas of different tempuratures and make sure there is a vapour barrier on the warm side between two zones that are maintained at different tempuratures.

Mold has become a real big problem ever since aircondition use became common and vapour barriers are on the wrong side of the tempurature transition line.

arnheimacres

TC - I think you may very well be correct. This has occurred since the AC has been cranked up during our recent heat wave. I think I have enough good advice here to take care of the problem. Thanks again to all for your advice.

copusbuilder

They actually say a 10% bleach water solution is more effective in killing mold than straight or higher combinations. This was what they taught us in my Mold Remediation classes.
There is a product called Microban that they sell in gallon bottles. This is the one they are using to treat all the buggies etc.

Tight housing is what they blame for the rise in mold in Houston. No breathing!

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maj

Exactly

With the tight building techniques going on, there MUST be some type of air exchanger. The moist air must be exchanged somehow with drier air. My guess with armheims problem is the warm, humid air in the crawlspace trying to get to the cool, dry interior conditioned space. There should be a moisture barrier on the crawlspace floor, continuing up to the mudsill, then sealed tight at the mudsill. Boxsill should be insulated with rigid foam & caulked tight.

maj

Humidity MUST be below 40% to prevent mold growth.

Double-A

I think that has happened only once in Houston in the Cenozoic Era.

Driving from just north Houston to League City (south of Houston) with no A/C in the summer, I'd have mold growing on me. Little Rock is not much better. I actually think its "hotter", just because there seems to be little to no breeze so much of the time.

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maj

I'm refering to INDOOR humidity. We can't control outside humidity, it's the indoor humidity that needs to be controlled through the use of air exchangers or dehumidifiers.

Double-A

I followed that maj My only point was that in Houston, the humdittie is so high all the time that if the wind stops blowing and you're standing in the shade, you're gonna grow mold.

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Zack

There are many ways that you can approach this problem. There are a lot of variables that can come into play when you are taking about mold. Check out this website www.IAQM.com for more information about mold growth and remediaton. I have seen mold in a lot of different places caused by many things. That website will help you better understand what you are up against.

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obermeier

You can spray the entire area with an octaboraite, either TIMBOR or the much less expensive TERMITE PRUFF. This will not only kill the mold and prevent it from comming back but will also effectively insect pruff and termite pruff the home so long as it is not washed off. It is enviromentally frendly and has no known ill effects on people.\
MIKE Obermeier

Savdog01

I ran across a similar situation recently. Upon inspection of a crawlspace I noticed the wood around a lot of the floor registers and a good bit of the duct work wet and dripping from condensation. The entire ground is covered with a black plastic moisture barrier.This home is located beside a river and we are in a high humidity area anyway. I contacted my HVAC contractor and he said that he has been running into this recently with the extreme heat we have been having combined with the humidity. To correct (?) the problem, he has had to close up all the foundation vents and install a whole house dehumidifier in the crawlspace. He said this would not pass our building code but it was what he had to do to take care of the moisture. I would assume this would also prevent any mold growth.

ApgarNJ

i have the same problem but haven't addressed it yet. we just framed an addition on the back of a ranch house. the main house has a full basement which is actually a 3 car garage, (it's on a hill) and our addition has a crawl space. well. the access holes from the full basement to the crawl weren't cut in, until we had it completely framed. when the mason came to cut the openings, i saw a lot of lying water on the crawl space floor, and some mold starting to grow underneath the subfloor sheating. we now keep all the garage doors open and the access holes are pretty big, so there is plenty of air flow now. i plan on running a dehumidifier once we get the windows/ext doors in this week. might have to go in there and spray some bleach solution on the ply. there are no crawl space vents because the grade is too high outside. the foundation has a curb on the top course so we sunk the floor into that cavity. what a pain to frame.

AndyJones

Best way to combat mold is to prevent if from growing in the first place. Check out this product, www.bluwood.net. It is applied to lumber (can be put on OSB, plywood, framing lumber, Engineered wood, everything) BEFORE the home is built and prevents mold from growing in the first place. Sure, it adds cost (about 20% to the cost of the lumber), but no more down days trying to figure out how to get rid of the mold.

ApgarNJ

never seen anyone using that stuff. you put it on at the jobsite or do you special order lumber already coated?
i would only think you'd need it on the underside of subflooring and the joists/rim of the basement. not that mold can't grow other places but those are the common problem areas. not very often do we find any mold just in peoples walls. at least not in this area of the country.
and very little ever found in attics.
all depends if they vent the attic or not.

AndyJones

You have to have your lumber yard order it pre-coated. I've seen people only do portions of a house (like just the sub-floor) and I've seen them do the whole house pack. Apparently, it also protects against termites and other insects from attacking the wood, is no more corrosive to hangers and fastenrers that regular framing lumber, and can be left at the job-site or in the lumber yard uncovered for up to 6 months in the elements and the warranty is still intact. Looks like the warranty is a life-time deal, and I think its transferrable from one homeowner to the next. Looks like a pretty good insurance policy to me.