Musty Crawl Space- Should I just open it up?


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Old 01-19-15, 08:59 AM
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Musty Crawl Space- Should I just open it up?

4 years ago we built a 20x20 addition off our house on sonotubes. The structure is about a foot off the ground. The builder suggested I just use some lattice to close up the opening but instead I used PT plywood. I didn't like the look of lattice and figured the plywood would help keep bugs, rodents and rain out. I buried the plywood about 6 inches down, screwed it to the structure, painted it and cut in some vents. Looked great...

Now, it is starting to get musty and stale under there. I can smell it through the carpet when I lay on the floor. I have a family and want to protect their health before this turns into a serious a mold problem.

Here is my plan: Remove all the plywood to open the space back up.
Check the floor insulation for mold. If it is moldy, tear up the carpet and subfloor and remove it. Paint all the floor joists with Killz and replace the insulation and sub floor. This time I will close the opening under the addition with lattice (with some bug screen/mesh stapled to the back).

Does anyone see a fault with this plan? Should opening the space up to the fresh air and leaving it that way prevent the problem from re-surfacing? What other concerns should I have? I realize I am now inviting small pests and frigid air to reside under my addition. I feel this solution is much better than installing membranes and dehumidifiers etc.... BTW, there is no plumbing under the floor. Please share your thoughts and suggestions. Thanks!
 
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Old 01-19-15, 09:22 AM
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Welcome to the forums.

You say there are vents in the plywood - how many and how many square inches?
 
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Old 01-19-15, 09:27 AM
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I would also treat the area for termites. The plywood should have never been in contact with the earth much less buried.
Is the floor insulated?
 
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Old 01-19-15, 09:34 AM
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The floor is insulated. I figured since it was PT plywood it would be ok. I thought by closing the space in I would be minimizing chances of termites etc...
 
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Old 01-19-15, 09:35 AM
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Tear out the plywood and then crawl under and see what you have.
 
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Old 01-19-15, 09:37 AM
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4 vents, around 12x6 inches each...Off the shelf ones from Lowes
 
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Old 01-19-15, 09:38 AM
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Glad you used PT plywood! It doesn't make a lot of difference whether or not the crawlspace is closed in when it comes to termites although they do prefer a damp environment over a dry one.
 
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Old 01-19-15, 09:51 AM
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Opening it up will as you say "I realize I am now inviting small pests and frigid air to reside under my addition." but I believe that is the best approach. The question then comes how do you air seal that floor assembly, insulate it, and secure it from critters.

There is an emphasis on air sealing as cold weather invites air flow from below up into the house. seal all holes and seams, super insulate it, then cover the bottoms of those joists with plywood. Might even use a layer of house wrap above the plywood to get more sealing.

Bud
 
 

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