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WillK 04-30-2012 10:49 PM

Crawlspace update
Okay.. I wanted to see if anyone can explain something about how things are happenning with my crawlspace and how that will change with addition of plastic sheeting and sealing the walls.

Our house built in 1917 does not have a foundation wall. The crawlspace is enclosed by stonne fascia which was installed over tongue and groove boards, the boards are mostly rotted away. The crawlspace floor is dirt. The furnace is installed horizontally in the crawlspace, it is 80% efficient gas burning forced air heat with no AC. When we bought the house there was no sump pit or pump, gutters were inadequate or improper, the crawlspace has 2 vents.

Since buying the house I've redone the roof and installed new gutters, plumbing problems which was resulting in sewage backup from a standpipe have been fixed, and I've installed a sump pit and pump with holes I put in at the bottom to allow water from the ground to be drained away.

So my observation since installing the pit is that the water that gets into the crawlspace (if any) during heavy rain does not cause the sump pit to run, but in the winter the sump pit runs regularly even when it is below freezing..

So what that leads me to believe is that the house is warming the ground around the house enough to melt snow which then infiltrates the crawlspace dirt.

The observations seem to suggest I don't have problems with rainwater drainage or surface runoff.

Long term the solution will be an exterior perimeter drain which will go in along with a foundation wall. I'm between jobs, that won't happen any sooner than next year.

First question: am I guessing right about what is happenning?
Next question: will the envelope of ground being heated by the house change when I install plastic sheeting on the ground in the crawlspace? My concern is that if that happens, groundwater under perimeter footings might freeze where it remained warmed before, and I might get frost heaving...

joecaption 05-01-2012 12:12 AM

Not going to change the temp.
It will help stop rising moisture from causing fungus and mold, also by helping to keep it dryer it will lower the chances of termites and powder post beetles.
Not stop them just slow them down.
All that rotted wood down there is a sure way to draw in termites.

WillK 05-01-2012 09:18 AM

Good point... as I'm cleaning out debris in preparation for the plastic sheeting I'll remove all the rotted wood from the perimeter wall, the stone layer seems capable of holding itself in place from the areas I've already taken the boards off anyway.

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