Building a basement in an area w/a high water table

I live in Savannah, GA and the area is situated on marshlands. This gives us a very high water table. Dig just a few feet and you’ll hit water. Basements are rare except in the downtown area (which is just built up over the river lever).

If I wanted to build a house with a basement in such an area, what would be involved? I’m sure it would be very expensive.

Well, if you want an indoor swimming pool, you’ll have made a good start of it.

There’s a reason why nobody builds basements in places like Savannah, as you already understand. Water seeks its own level. It is also patient. No matter how much of a seal you put on your basement, it will eventually fail and you will pay the consequences.

These days, I’ve seen houses built (on This Old House and on Hometime) in which the foundation is built, then a sealent in the form of a sheet of high-tech plastic or a spray is applied to the outside of the house. Of course, to do that, you have to dig a trench around the foundation, and if the lot has water table higher than the floor of the basement, you (or your contractor) will find himself swimming in mud very very quickly.

There is also the problem of condensation. The sealant may keep the water out, but it won’t keep out the condensation, which will give you a mildew problem, which in Savannah means sudden overnight appearances of mold-based civilizations that will want to negotiate sovereignity.

This is a problem in which the best solution is to not to cause the problem in the first place. Add an extra floor on top, to make up for the one you won’t have on the bottom.

What you would need is to install de-watering wells at the 4 corners (or more depending on the size) and draw down the water table around the basement. The water could be discharged to a stream or even to a recharge basin away from the wells.

Around here people who build in the old river towns import a small mountain of earth, then build the basement inside it.

The best exterior treatment for basement walls is bentonite clay ( cheap, non-toxic, long-lasting, and water impermeable), which you can buy in bags from any well driller. You mix it into an oatmeal consistency, trowel it on, then cover it with plastic so it stays moist and doesn’t flake off before you backfill. Then place styrofoam panels, at least 2" thick, to discourage condensation from the temperature differential.

Place drain tile by the footer, and maybe halfway up the wall if you want to be really anal, and backfill with as much sewer rock as yu can afford.

I don’t know Savannah, but this DOES work in southern Wisconsin, with humid summers.

When I lived in Woodbridge Township, NJ the water table there was very high also. Just about every house in the area had a sump pump in the basement.

I live in Richmond Canada. We’re actually below water level by a foot or so. (Large extensive network of pumping stations and dykes keep us nice and dry). No on here has a basement. It’s just that simple.

I suppose with enough money, one could easily build a basement. All you would need to do would be to dig a very large stainless steel box (or another rust-resistant metal) into the ground, and that would serve to keep the water out.

It sounds like k2dave and leroy have some solid advice for you. The gist is that it can be done, but it will cost money.

I live in Houston which has a high water table and where the downtown area has an extensive underground tunnel system that works well. During ghastly weather emergencies it can become a mess (as when Allison hit us a couple of times last summer). And, although they’re rare here, I do know a person who had a basement here. It definitely had that “place that’s been wet” smell. If you do it, don’t keep your valuables there.

As you have seen from previous comments, you can have a basement. Building a hill is the only method I would recommend. You would have a problem getting a reputable contractor to build anything below the water table, because water will ALWAYS find a way to get in. If you pump it out, you will have moisture. Where there is moisture, there WILL be mold. And mold is not nice if you have allergies, or so I’ve read. I’m a carpenter, and I have actually worked in Richmond,BC. There are very good reasons for their by-laws forbidding basements. Their first level is sometimes referred to as a basement.

Leroy and Lauri have it. Un-level the ground (so to speak) by making a hill to bulid your house on (and basement in). Put in a sump pump that dumps a distance away and down from your house.

Of course, this is a procedure best carried out when a parcel of land --usually large— is set up for building a whole set of homes. I lived in Waldorf MD, in an area that has wetlands in and around it. When they opened up the land for development, they bulldozed where the roads would go and heaped the earth by the sides of the road and into little “hills” where each house would go. The net effect is that most homes have basements of one sort or another that are underground, but are more or less at or above the street level. And the cement foundations/basements are by code sealed on their earth sides (outsides) to prevent or at least preculde seepage of groundwater. There are drains that let water falling down the “hills” and go back into the creeks, etc. It worked well.

You could get a really big parcel of land and dig a big hole for a pond or lake on one part of it, using the excavated earth to make yourself a hill in which you could put your basement. You could do this if you had the money.

…Or you could build your own little hill on a smaller parcel of land and let the runoff go into your neighbors’ homes. That would last about one or two good rainstorms, assuming you got it past the building inspectors in the first place.

Bottom line: As a practical matter, you probably have to incorporate the desire and design for a basement into the design of your entire housing development, as opposed to just a single home.

I’m going to agree with benlormat.

One of my first jobs was installing sump pumps in basements. If you pick a lot with some elevation, have a “good” contractor use the proper sealant methods, and install a sump pump it should be relatively easy.

Now if the water table is so high it’s pushing up caskets and such it may be a bigger problem. In places like Houston where flash floods are expected you may be looking at building a hill and or serious pumps like the others have noted.