Location: Asheville NC
Crawlspace: Dirt Floor, Block Walls (semi-buried as I am on a hillside), Wood Floor Joists above. Exterior walls above block walls are Masonite.
Size: 30×30 with about 10×30 usable with 7 foot ceilings – the other 20×30 is about 4 ft high.
Environment: Water heater and central air pump are located down here. I think the builder left large gaps where exterior siding meets the foundation walls which allowed way more ventilation than I ever wanted (or perhaps this is just poor carpentry). I installed a dehumidifier when I moved in 5 years ago but it has been a constant battle to keep it below 50%. Recently, I have already sealed the vents, electrical plugs to exterior walls, and holes for plumbing, electric, cable, phones into the interior walls overhead. It is mid Feb and temps are rather warm in the 50s but the temp in basement is about 60. Much improved over the low 40s temps I was getting. I have 40% or lower humidity readings now. The goal is to get the humidity readings down to 30%. I intend to use this as a workshop and pantry area so having it semi-conditioned is the goal.
Radon: Tested for Radon 3 years ago and will do so again after this plan below is finished.
Please provide critique/feedback on my plan. I want to make sure I am not making mistakes or missing other opportunities. I have been researching here and other places like crawlspace.org and came up with this approach. I also have a few questions below.
Floor: Cover dirt floor with 6 mil black poly. Seal the seams with 3M duct tape. I will stake the poly to the floor with 6 inch landscape stakes and cover those places with duct tape. I will cover part of the floor that is usable with a 10’x30′ treated wood floor built on concrete stone supports. This will have black poly underneath as well.
Walls: 6 mil Black poly with 3 inches expose at top of the wall for termite inspection. Will paint that 3 inches with white sealant paint for easy termite inspection and to provide vapor retarder. All seams on the black poly sealed with 3M duct tape.
Foundation Wall to Floor Joists area: Where the floor frame sits on the wall there is of course a small < 24″ area where the exterior side is mounted to particle board. This is either un-insulated in some places or at the least under-insulated. I plan to cut and piece in foam board there and put some additional backed insulation pieces. This should cut down on the cold floors the house seems to have. Ideas here are particularly appreciated. Questions: Opinions on the above plan? What should I use to glue the black poly to the walls? Double sided Tape/DAP adhesive/other product?? Should I attach foam board to the black poly walls to add additional insulation to the space to add to the conditioning of that space? Thanks JW
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