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Difficult Crawlspace Access

user-1091831 | Posted in GBA Pro Help on

I have a Vermont customer who has requested that the crawlspace below their kitchen be insulated to improve to reduce cold floors and general discomfort. My biggest issue is the clearance in the crawlspace between the soil and the floor joists. I’ve recommended 3″ of closed cell foam to the crawlspace walls and rim joists/box sills. I would recommend poly across the dirt floor and up the walls first, but my issue is the clearance. It simply isn’t feasible to properly layout poly along the floor as there is less than 1 foot of clearance in most areas. We have to excavate around the perimeter just to get to the crawlspace walls.

What I’m questioning is the possibility of mold growth and moisture since the crawlspace floor will still be exposed, and the walls will no longer be leaky. I am aware of potential soil gases. It is about a 300 SF crawl with just one point of access from the basement, so I don’t suspect there to be much air exchange there. The crawlspace walls from the outside appear to be poured but it appears to have been done over an existing rubble foundation. Any thoughts? The thought of open cell foam has crossed my mind, despite its lower R-value.

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  1. GBA Editor
    Martin Holladay | | #1

    The first step is excavation. You need to lower the crawl space floor. This is done with an entrenching tool or a short-handled hoe, and the dirt must be removed in 5-gallon drywall buckets. Do you know any teenagers who work for minimum wage?

    Once the floor has been lowered, you can assess the situation and properly address moisture issues, floor poly, and wall insulation. I'm a great believer in lighting crawl spaces well. If the budget permits, get an electrician to wire 6 or 8 lights.

    More information here: Building an Unvented Crawl Space.

  2. user-1091831 | | #2

    Hi Martin,

    Thanks for your response, ideally this is what I would like to do but there are a few stipulations preventing me from doing so. 1) This job was one taken over by a former employee who generated a proposal at a cost that simply does not include the time and material for all of this excavation. The customer has based their budgeting on this cost and is not open to increases, despite our reasoning. Frustrating. 2) There are stone piers that seem to reinforce the floor joists and I would be hesitant to excavate near and around those for obvious reasons.

    So I guess to rephrase my question, since there is no budget to do it 100% correctly, do I risk mold development within the crawlspace without installing poly on the floor? I'm in a pickle where not doing any insulation to avoid an issue isn't an option either. Thanks

  3. GBA Editor
    Martin Holladay | | #3

    Q. "Since there is no budget to do it 100% correctly, do I risk mold development within the crawlspace without installing poly on the floor?"

    A. Yes.

    When a client says, "I can't afford to do it right. Please do it the wrong way, because that is all I can afford" -- that is a clue that it is time to walk away from the client, saying, "Good luck finding someone to perform the work the way you want it done."

  4. davidmeiland | | #4

    I wouldn't do it either. The house is too low to work under. If you have any choice at all, find somewhere else to work. If they were talking to me, I would be presenting options for lifting the house a foot or two, which is easily $10K if not a lot more. After that's done we can properly repair framing, plumb, wire, insulate, install VB, etc.

  5. user-1091831 | | #5

    Thank you both for the responses. I wish lifting the house or walking away were options for us. The first is WAY beyond the given budget and the latter is not an option as they are a long time fuel customer of ours and walking away wouldn't look good. Looks like we'll probably lose our shirt on this project to take the time to do it right for the client. Thanks again.

  6. davidmeiland | | #6

    I'm just curious, if you can get a spray foam installer under the house to spray the rim, can't you also get the plastic on the ground? I know it's tedious, but cut and unroll the piece(s) first, then push them ahead of you as you slide along toward the far corners. Or, slide all the way to the far corner and then use a rope and a spring clamp to pull the material towards you. Yes, it will be as bad a day as you ever had at work, but it can be done.

  7. user-1091831 | | #7

    Thanks for the advice, much appreciated. To get the installer in there we had man hours figured to excavate around the perimeter of the crawlspace so that they could at least insulate and seal the walls. As I eluded to previously, with the budget the customer has set, there was no additional labor time available to excavate any more than that, hence the difficulties of laying poly in an 8" space at the middle of the crawl.

  8. davidmeiland | | #8

    I gotta be honest, that type of trenching around the inside of a foundation concerns me. I would do some test digging to make sure you're not going to be undermining the footing anywhere, and there's also the risk that the new low area you create will attract surface water that didn't used to migrate in. The whole thing could easily get worse for all the trouble. Don't ask me how I know.

  9. nvman | | #9

    Do you have good insurance if something goes wrong if the work you attempt does not go right?
    Is it worth the risk to attempt a job that has a chance of failing?

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