DIY Crawlspace Encapsulation
I have a few questions regarding a homeowner crawlspace encapsulation, there are quite a few things at play here but I’ll try to keep it brief while giving as much info as possible. Last year I bought a 1970s ranch in Ontario, Canada, 6A. I am a carpenter by trade and knew when buying the house that the crawlspace was not sealed and that someday it would have to be done, I figured I’d tackle it this summer (hopefully by myself, but I’m certainly not opposed to hiring professionals if necessary). The top of the footings are pretty much at grade, not sure how deep they are, bedrock isnt far, looks like there has been some movement but as far as I can tell no bulk water coming in from the CMU walls or footings. Walls are about 36″ high, ~800sqft of floor space, no signs of any standing water, slight mildew on some joists but nothing alarming. The house is heated with baseboard and wood, no a/c unit. The previous home owner wrapped the entire house with 3″ of XPS right down to grade, so it is ‘insulated’ down there, also there are additions on two sides of the house, meaning that only two walls of the crawlspace are actually ‘exterior walls’. The vents were sealed by the previous home owner, the craftpaper fiberglass was removed from the rim joist bays. There is no sump pump and probably no weeping tile on the outside of the footing, but I doubt that is a problem seeing as it is ‘dry’ down there. My plan was to clean out the debris down there, staple 12 mil poly to the sill beam, covering the dirt and taping seams, add a standard 2500 cuft dehumidifier and run the hose to the kitchen sink drain which drains into a small gravel pit in the corner of the crawlspace. Having been down there for two days cleaning an unforeseen and truly absurd amount of garbage (anyone need an old exhaust manifold?), and being confronted with a massive decommissioned oil furnace, I started having second thoughts. Here are the concerns:
1) In order to get rid of every small bit of debris I would literally have to dig out the dirt over the entire surface of the crawl. There are probably thousands of little pieces of wood/plywood/osb/fiberglass amongst and buried in the dirt. If the VB operates as it should, water will condense on the dirt side of the poly. Will that promote mold and rotting underneath the VB? Concerns that it will affect the well water quality (we are on a shallowish well)? Should I care?
2) Will the upfacing side of the VB become a condensing surface in the winter, as the warm air from the house meets the cold dirt?
3) Will the underside of the sill beam rot if I staple the VB to it? To me it is ideal as then I don’t have to hammer drill and fasten to the CMU.
4) What the heck do I do with the old oil furnace and how to I detail around it if I decide to leave it? Is there a concern with leaving it? The crawlspace opening is only 2ft x 2ft, so it would need to be removed in pieces. The oil tank is gone, it looks to have been kept outside, however there is a valve and copper pipe with an oil filter that runs from the CMU wall, so far the copper pipe looks to be in tact but will rot out some day.
5) Any concerns with connecting a dehumidifier to the kitchen drain, which just runs into the gravel pit in the crawlspace?
Thank you for reading and thanks in advance for any advice. I am a long time reader and first time poster.
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