Poindexter versus damp subarctic crawlspace

[AlbergSteve]

Found some grey/black slime growing in the condensate tank this morning. Rinsed that out with with some white vinegar and prefilled the tank with a pint of 50:50 vinegar/water poured in through the condensate path.

I haven't found a desirable adhesive for attaching plastic vapor barrier to poured concrete. I spent a bunch of time at Lowes-Depot reading labels on adhesives. The short version, my findings, only the most expensive glues are rated for plastic to concrete, and none of them are rated for damp environments.

I do have another local store still stocking tremco "black death" acoustic sealant. Seems like my best current bet, but will need to wait until spring so i can pull the worst of the vapor outgassed from that out of the crawlspace through a ventilation fan that doesn't exist yet without stinking up the house so bad.

Interim, I did crawl the perimeter where the floor vapor barrier meets the poured wall and pushed the plastic back onto the glue line.

Hygrometer set due Monday. I do have one contractor at my church who is willing to excavate foundations and grade lots as part of his landscaping business. I hope to speak to him tomorrow.

For now I am maintaining RH in the crawl at <40%, at 60-65dF, and pulling 50-60 pints out of the dehumidifier weekly. Dehumidifier should settle down once the ground freezes. I know I will be running the dehumidifier again from when the ground thaws until I can get vapor impermeable barrier on the exterior foundation wall.

After that I will still have capillary transport from under the footer into the sill plate. Planning to place drain tile at the exterior perimeter to minimize that as much as possible. Without lifting the house off the foundation to place a capillary break, that is all I can do to keep the sill plate dry.

My rim joist is dry, except for what gets carried through the sill plate. Planned interventions to keep the sill plate dry:

1. Grade lot so sill plate is 4" above grade with 2" in 12' slope away from house on all sides, gravity drain surface water to street.
2. Water impermeable barrier on exterior foundation wall to top of rim joist, with insulation.
3. Drain tile at footer, full circumference, gravity drain to sump adjacent to utility easement.
4. New vapor barrier on floor of crawlspace. I think I am going to put the vapor barrier as low as possible on the poured wall. I know there is water in that concrete. If I can get any of it out the side wall without carrying it through the sill plate first I think I would rather do that.
5. Dehumidifier remains on standby.
6. Possible seasonal ventilation fan. I am not opposed, but I think the number of days i can operate one without pumping net water into the crawlspace is probably very low.

Excavating around the foundation is the best way to attack this problem - deal with it from the outside. Drain tile is a must. When we do drain tile here in BC, we're required to place the pipe in a bed of clear crushed 3/4'' drain rock wrapped in filter cloth. The filter cloth prevents the soil fines from entering the drain tile over time. If it's not too much work, I'd probably remove the old insulation from the foundation, seal any cracks and form tie ends with (broken link removed to https://www.xypex.com/products/details/xypex-concentrate), apply several coats of damp proofing, and reinsulate with rigid insulation and cover with Delta drain. This is how we've been doing it here for the last few years. I'd seriously consider pouring a concrete ground seal on the poly in the crawl space.

There are some helpful tips here, although they don't show the use of Delta drain in in any of the diagrams, I wouldn't build a basement without it. Note also they recommend 10% slope for the first 6 feet away from the house. The code in BC for grade against the house is 8'' to bottom of sill plate, 4'' if it's to a hard surface, ie. a concrete sidewalk.

I'm starting my own basement reno next year, blank slate on the inside right now.


This stuff is your friend, I'll be "painting" all the concrete with Xypex.

 

[Poindexter]

Thanks @AlbergSteve . I was kinda leaning towards a thin layer of concrete in the crawl over the vapor barrier - until I found a couple spots of standing water above the dirt but under the vapor barrier in the crawl a few days ago. Largest is about 2x2 feet and half an inch deep.

First question every pro asked me "Do you have standing water between the dirt and vapor barrier?" and I always honestly answered no.

I did have a guy out last weekend to look the thing over. He thought total $2-3k for just the dirt work. I would have to scrape the UFFI off the exterior foundation, apply whatever product, put the drain tile in the trench and come up with gravel with no fines in it for the drain tile and a bunch of landscaping fabric, and a PVC pipe to go down in the cistern, and boulders to fill the cistern, and more landscaping cloth there.

For now I am on hold waiting for freeze up. Once the ground is frozen I can turn the dehumidifier off.

Come spring I will punch some holes in the rim joist, install a couple fans and then use a nasty glue to secure new vapor barrier to the poured concrete. Run the fans to pull the glue vapors out from under the house. Once the ground is thawed we will excavate and blah blah, have all winter to choose products for the exterior.

Hopefully one year from now I will have no musty smell coming out of the crawlspace, and not be running the dehumidifier to achieve it.

 

[AlbergSteve]

Thanks @AlbergSteve . I was kinda leaning towards a thin layer of concrete in the crawl over the vapor barrier - until I found a couple spots of standing water above the dirt but under the vapor barrier in the crawl a few days ago. Largest is about 2x2 feet and half an inch deep.

First question every pro asked me "Do you have standing water between the dirt and vapor barrier?" and I always honestly answered no.

I did have a guy out last weekend to look the thing over. He thought total $2-3k for just the dirt work. I would have to scrape the UFFI off the exterior foundation, apply whatever product, put the drain tile in the trench and come up with gravel with no fines in it for the drain tile and a bunch of landscaping fabric, and a PVC pipe to go down in the cistern, and boulders to fill the cistern, and more landscaping cloth there.

For now I am on hold waiting for freeze up. Once the ground is frozen I can turn the dehumidifier off.

Come spring I will punch some holes in the rim joist, install a couple fans and then use a nasty glue to secure new vapor barrier to the poured concrete. Run the fans to pull the glue vapors out from under the house. Once the ground is thawed we will excavate and blah blah, have all winter to choose products for the exterior.

Hopefully one year from now I will have no musty smell coming out of the crawlspace, and not be running the dehumidifier to achieve it.

Yeah, standing water in there is not a good thing! 2-3k for the excavation seem like a really good price.
Most landscaping outfits will have 3/4'', free draining crush, or your local concrete ready-mix supplier.
There are latex based acoustical sealants with low/no voc's that you could use to seal the VB to the concrete.
And don't forget the Xypex, it's amazing stuff. I've used it to stop/block running water in an elevator pit that was 4 feet below drain tile.
Keep us updated.