Fill Soil for Crawl Space With Standing Water

[donbhere]

The soil in my crawl space has standing water around the foundation and in some low lying areas. The low lying areas are approximately 4" below the the outside grade. The water around the foundation is there because the footer trench was never back filled. In the low-country, a two foot deep hole will fill with water.

Before doing anything else, I want to raise the crawl space floor to above the outside grade and backfill the footer trench. I called to bring in soil and the guy told me the best thing to use is sand. Is this correct? It doesn't seem that sand will do much for keeping the water out. The existing crawl space ground has been covered with 1"-2" of sand and then covered with a moisture barrier (which some is under water).

Water is kept away from the house except one area where the driveway butts up to the front of the house. Water does build up in that area during rains.

Thanks,

Don

 

[LCruiser]

True - sand is not going to keep the water out. However, neither is anything else. Sand will provide some stability, but the water level will not go down. (I'm making some assumptions about your situation) How about a sump pump? The volume may not be great - it will just continue until the level equalizes.

You can't keep water out like that. You have to take it. Take it and pump it out.

 

[boffintech]

Flowable fill (aka lean conrete) will keep the water out. And the best part is you can pump it to the exact location that you need it.

 

[bltseattle]

You say the footer trench has not been backfilled. Is it possible to install a perf pipe with positive drainage, then backfill with drain gravel, to daylight somewhere away (and downslope) from your house? This may be possible unless your house is at the lowest spot on the site, and a proper system would keep water from getting under your house. A ditch witch could make short work of extending your foundation trench to where it can be daylighted. This action in addition to a sump pump for the crawl space itself seems like it would be a possible long term solution... no floor raising needed

I dont' think this would be too expensive a solution but I would not try to cut corners. You don't want to let mold get started, that stuff is seriously toxic and can be impossible to get rid of.

 

[cvg]

apparently your groundwater table is very high and the standing water you see is groundwater, not from storm runoff. sand won't do anything to solve the problem, except eliminate the standing water. Neither will flowable fill.

If your foundation is constructed below the water table as it appears, installing the french drain as suggested may lower the water table a bit. However, unless you have experienced settlement or other structural problems with your foundation, it may be ok to leave it alone and not try to dewater it.

You should take care of the ponding issue on your driveway as soon as practical.

 

[Ron]

Fundamentally, you have a drainage problem! You must drain the area under your footprint or you will continue to have problems.

Having said that, you must have a positive outfall in order to use a french drain or other drainage means. The lot should have been filled to at least 1 foot above the crown of the road in front. If that wasn't done, you'll continue to have problems.

If you have a ditch or positive drainage at the road, you can cut shallow swales in your lot to provide some mitigation of the issue. I prefer swales to french drains as they don't require much maintenance and you can always see when they aren't working.

Once you do that, you can backfill with clean fine sand.

Obviously your vapor barrier isn't working. You will have problems with wood floor structures placed above your crawl space. The will likely warp and eventually rot.

Your crawl space must be vented to reduce the accumulation of moisture in there as well. In your area, you should have 1 square foot of vent area for each 150 square feet of floor area for static venting situations. However, you will likely need some forced draft ventilation to keep up with your condition. I would suggest a forced draft fan hooked to a humidistat, set to keep the humidity below a certain level, say 65%.

You'll still get condensation sometimes, but you'll reduce it significantly.

Filling with anything (sand, gravel, flowable fill, even concrete) will not solve your problem....positive drainage will.