Insulating a crawlspace prone to flooding
 

Hi everyone,
I live in an 80 year old house located in the floodplain of a small creek. I am not exactly sure why, but but flooding wasn't a problem until about 2 years ago when I moved in. I think this is just a case of correlation, not causation. There has been development upstream from my house for the past 10 years--the biggest culprits I think are parking lots. Downstream, the city operates a pumping station that pumps the creek over a levee when water levels are high. The pump is as old as my house and we think it is getting overwhelmed.

Suffice it to say my crawlspace and partial basement have flooded 3 times in the past 2 years. The most recent time, water levels went above my crawlspace wall.

I am looking at sealing and insulating my crawlspace with an eye to:

1. Reduce the risk of flooding
2. Get rid of water when it does get in
3. Insulate the crawlspace and add it to the conditioned space

I have started by putting down 6mil plastic on the dirt floor to make it a more pleasant working environment. Next I guess I will seal the plastic on the floor with some sort of adhesive, insulate the walls with foam board, insulate between the floor joists and the foundation wall, and run a vapor barrier from the top of the wall to the floor.

There is a pretty good slope to the crawlspace and water collects in a low point. I guess a sump pump is in order.

Anyhow, has anyone dealt with a similar situation or have any suggestions?

Can you waterproof the outside of the basement walls?
Otherwise what you are doing sounds about right, use foam board that is intended for use below slabs (usually blue), water will not soak into it.

Does the house have proper drain tile and sump that works good?

Lots of work...
 

I could waterproof the outside - any suggestions on what to use?

It does have a drain to the sanitary sewer in the basement, but no sump. I think getting the sump in is probably my next step. It is going to have to wait until the deck is finished though.

If the walls are masonry or concrete, you could paint on an asphalt emulsion, If they are stick built it may be more difficult, what is the outside finish on the basement walls?

The foundation is solid concrete--though it is cracked in some places from settling over the past 80 years. I would have to cover the asphalt emulsion with something (not feathers) to keep the wife happy--I don't think she would go for a tar covered house. I did something similar at my last house below grade. I used tar and then attached a thick rubber sheet to that.

For the outside you should seal the cracks, I found that 6" wide butyl rubber tape with foil backing for going around sky lights works really well for going over cracks after you repair them either with mortar or with polyurethane caulk that is designed for concrete repair.
On my house after I sealed the cracks I taped 6 mil plastic up a few inches on the walls covered over it with ridged foam going down about a foot below grade, brought the 6 mil plastic out away from the house about 6 feet, sloping away and at that outer edge of the plastic put your drain tile, over the plastic put your 2" foam tape the seams and put another layer of 6 mil plastic, that way you keep the foam protected from roots and have dual layers of water protection that push the water away from your house towards the drain tile, the foam also insulates the ground around your house so your foundation walls never get cold.
The above grade foam can be covered with stucco, latex stucco, fiberglass foundation covering, aluminum flashing or you can even buy foam insulation that already has a pea gravel or sand covering on it that is bonded to the foam.

I like what Ryland says, esp using urethane caulking on the cracks, you could use an elastomeric paint on the outside, even comes in pink if swmbo demands, there are several brands, dryvit is probably one of the high end products, you could even do an outsulation job using foam and latex stucco.
I have found that plastic tarps can be bought cheaply if there is a surplus store or farm supply discount store near you, and they are much more durable than plastic sheeting.

Do you know what this product is called (brand or generic name)? I have heard of this, but I wasn't able to find it searching online. I think I will need a gravel coated foam sheet or something similar to insulate our home's concrete footing.

Thanks,
Tim

No idea what the product or brand is, I just bought a sheet of it to cover over what used to be a basement window and it was about $11 for a 1" thick 2' by 4' sheet... most home improvement stores should have this stuff, or be able to order it, but the sheet I bought just had a bar code on it.