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Community and Q&A

Legacy Sleepers-over-dirt Crawlspace Situation

Jeff_m191 | Posted in General Questions on


First, love the site, I’m not a building professional by trade (but am technical), and I find the discussions and resources here invaluable as I work on my own home. 

Question for you all about how to “satisfice” on a project of mine:

I have a kitchen add-on (“shed”) built ~1920 or earlier, where the floor is made  of 2×6 sleepers laid on dirt. The original builder put a layer of tar paper-faced 2x10s over that. So it sort of has a vapor barrier? 

I’m calling this space where the sleepers live my “crawlspace”, fully aware it’s not to code (no 18″ gap, untreated wood on dirt, no vapor barrier over the dirt, etc etc). But it’s been there for decades, so it passes the test of time at least. 

My question: as reading this site would predict, the crawlspace is humid, and musty smelling. A humidistat reads in the low 60s usually.

Should I:
1) Ventilate the crawlspace to the basement (directly adjacent) where a dehumidifier will remove the moisture? 

2) Push air from the basement into the crawlspace to dry it out; worried about the smell migrating to my living space in this case.

3) Pull air from the crawlspace and ventilate it outdoors? Will this draw in moist air from outside? 

4) Something else?

Again, I’ve read enough here to know none of these are the “ideal”, but given I have no room to work under this space to do the proper thing, wondering what the next best alternative is if that makes sense?

I’m in Philly, so zone 4a. 

Thanks for any advice!

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  1. plumb_bob | | #1

    Hard to predict results for a situation like this, but I would consider running both supply and return air into the space. This would hypothetically balance the pressure while exchanging air, which would remove moisture and freshen things up. Putting this space into either positive or negative pressure would be an experiment.
    There are HRVs designed for small spaces, you could look at installing this into your crawl. This would also help mitigate radon if present.
    Hope to see what others chime in with.

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