[MichaelTP]

My house is in an area with a very high water table, and my crawlspace (cement floor) regularly has water in it. Sealing cracks in the floor, running french drains etc are excercises in futility where we are, so life is about sump pumps and a dehumidifer.

I'm interested in reducing the amount of wet floor I have down there...I want to tilt the floor slightly so all the water runs down to one side (from where it will then find its way to the sump pit.) I'm trying to reduce standing pools of water to reduce the need to dehumidify. I'm thinking of putting down cement (imagine a square 10 feet across) that is elevated an inch or two at one side. How do I do that? I am a cement/concrete newbie.

All suggestions and thoughts appreciated, thanks!

 

[CplDevilDog]

Is there currently a vapor barrier down such as 6 mil poly plastic or other?

Cement might be overkill, if you just slope the floor to one side, add a couple of drains and a sump. Throw plastic over it all.

Sorry, I re-read your post. Looks like there is already cement down. Is there a barrier under it? Could pour resurfacing concrete on top of what's there but if no barrier was down originally, it's still going to let humidity through.

 

[MichaelTP]

I don't know what's under the cement floor, but it lets water through so humidity is certainly also there. What I hope to achieve with an angled floor is to eliminate a ten square foot pool of water that is surely a major source of humidity down there...instead the water, once through the floor, would run in a much narrower space to the sump pumps.

My concern (having never worked with concrete) is that when it's wet it will level itself. I need to create an incline.

 

[CplDevilDog]

If the original slab is bleeding water and moisture through it or cracks in it, any concrete poured on top is going to fail.

If you're going to pour concrete anyway, I would remove the original and start from scratch.

 

[MichaelTP]

If the original slab is bleeding water and moisture through it or cracks in it, any concrete poured on top is going to fail.

I'm not concerned with it letting water in (as you said, it's going to...this is a fact of life where I am) What I'm going for is reducing the size of the puddle. With the floor as it is now I have large sections that stay wet with half an inch of water on them until the water evaporates...it doesn't run to the sump pit. With an angled floor I intend to direct the water to the pump so it's in the crawl space for minutes instead of days. So my question is: How do I lay down cement so that one side is 3" higher than the other side (ten feet away)?

 

[CplDevilDog]

Clean the concrete surface and apply a bonding agent to allow the new concrete to adhere.

Stack (2) 2x6 3" high for the "high side". Rip OSB or plywood from 3" down to nothing for the sides of the form. After some setting has occurred, remove the side boards and feather sides out with extra.

Use a sand mix with very fine aggregates. Keep your mix on the dry side and it will stay where you put it. Use a screed board to "pull" the mix across your side boards.

In two years you can use a coal shovel to remove the broken pieces and assorted slurry. One year if you live in the North. :thumbup:

 

[CplDevilDog]

Sorry, didn't mean to come off so harsh, but it is a lot of work and effort that will not last long.

 

[MichaelTP]

I appreciate the humor and the information!

Got any alternative suggestions? Water coming through the floor is a fact...the hydrostatic pressure is enormous when the water table rises. I think having a stream in the crawlspace would mean less humidity than having a lake.

The location of the entry points for water are known. Could I glue guides (any raised waterproof material a couple of inches high) to the floor to channel the water to the sump pits?

 

[CplDevilDog]

Of course there are several things to consider.

1) Budget
2) Timeline
3) Working space
4) Access

If it were my place, I would

1. Drill a test hole in a the slab to see if there is a barrier present.
2. If no barrier and the budget is there, I would seriously consider removing the floor. If you are not using the area for storage, etc. I would not replace it. I would put in de-watering system, vapor barrier
3. If the budget is not there, could you put a sump pit at the center of the low spot? Run the discharge across the floor to the low side of the foundation.

Maybe even consider cutting in french drains through the existing slab and routing them to the sump. Cover with vapor barrier and pea gravel.

 

[tpolk]

if the slab is thick enough you could cut channels for the water to follow. if possible you need to get a laser level to see real slab elevations

 

[MichaelTP]

if the slab is thick enough you could cut channels for the water to follow. if possible you need to get a laser level to see real slab elevations

Why didn't I think of that? Good suggestions (will an angle grinder with the right wheel be sufficient to cut a half inch channel?)

 

[Red Squirrel]

If you have that much water I would find out the actual spot it's coming out of (small hole in floor, or from wall?) and mitigate it from that point. Even if you were to slope it, that part of the floor would keep getting wet, and so would any items on there such as cardboard boxes and such. A source of mold right there.

 

[MichaelTP]

Red Squirrel, this is a crawlspace in a high water table area. Nothing is stored down there. Water is entering from 4-5 different points, and will not be stopped when the water table is high. My goal is to route the water to the sump pumps as effectively as possible.

 

[CplDevilDog]

Unless the water table is a pond, I still think you will have better luck with addressing the source.

Google search de-watering techniques or "lowering water table".

Depending on which solutions you choose, you may find the work is comparable or easier than just constantly fighting the symptoms. Better long-term results as well.

 

[CplDevilDog]

Here's the first result I found. I didn't bother to read it but it is a good example of how easy you can find good resources.

http://www.ehow.com/how_5959496_artificially-lower-ground-water-table.html

 

[CplDevilDog]

Also search "ground gutter" A fancy french drain.

I am putting one in now to address a steep slope to a foundation.

 

[MichaelTP]

Thank you for the thought (lowering water table) but as I mentioned at the outset, it's a fact. The home is 75 yards from a tidal inlet. The entire property is in a zone regulated by both local and state environmental agencies. Conventional remediation for crawlspace water does not work. It is a certainty that at certain times of the year there will be water coming into the crawlspace of my home and of all my neighbors homes. The best response to this that I've seen has been a well-contoured floor that causes all the water to drain to the sump pits...this is best because as soon as new water stops coming in, the space dries out fast (everyone uses dehumidifiers). I have standing water (because my floor does not route water to the pit) and that water has to evaporate (ie contribute to overall humidity) to leave. I want to pump it out, not remove it from the air.

 

[MecGen]

Hi Micheal

I used a die grinder and 3 inch cutting wheels to channel a "ditch" in my concrete, moving standing water to a drain. I would not do it again.
#1 took HOURS, dirty job, full face mask, hands vibrate for hours after.
#2 you still have to angle the pitch of the ditch, as well make it deep enough as not to have standing water in the ditch itself (is that clear?) lots of fiddling around, grinding here, just to make another high spot there.
#3 my ditch gets plugged/blocked on a weekly basis by dirt and debris.

IMHO...Cut a hole in the middle of the lake and put in a sump pump, or use a cement quick saw, cut a 2 inch wide track completely through the slab, put in a 2 inch abs pipe, cut in half or drilled will holes, sloped/graded properly to the area you want.

Not too many low cost solutions only band aids, standing water sucks

Good luck
Frank

 

[CplDevilDog]

If there is truly no way to lower the water table, that would be my suggestion as well.

Sump pump under the puddle and enough french drains around it to funnel water to it.