Water in my crawl space: how best to drain it?

Investorguy · Mar 24, 2006

Okay. I chatted about all this w/ my father in law.

He said the cement idea sounds the best to him. He is 100% convinced that it's the water table.

He said if you pour cement UP TO the water table, then the weight of the cement will displace the water without danger fo floating or breaking up. Obviously my little pad of cement isn't going to raise the entire area's water table. even if the water were to rise up though the cold cracks where the new cement meets the old cement, as long as the top of the cement was above the current water table, we should be okay.

This would be somewhere between 6-8 inches of seven sack concrete. Good thing there is that it could be pumped in via a vent and w/ a hose we could put it exactly where we need it. Wouldn't likely take more than a day.

Obviously we'd have to wait until it dried. He says that we could then throw the concrete right on over the vapor barrier.

I have to admit that I gravitate toward these more simple solutions. It would probably be ideal cost wise to spread a couple inches of crushed rock down there as well below the concrete.

So, given that analysis of the water table situation, does that sound reasonable?

How many yards is 6-8 inches by about 1600 sq feet?

I'd run this by an engineer before I did it, of course.

This would also solve the problem of having to rebuild the cripple wall. And posibly create a nice little (or rather large, I guess) storage area. If I go to sell I could advirtise an "unfinished basement". Well, maybe not. /forums/images/graemlins/smile.gif

Investorguy · Mar 24, 2006

( Is there any pitch to the concrete. Some place where if you did put a sump pump it would drain to it? )

No, it's all pretty flat down there. There's two large lakes and one long skinny one between the two cripple walls.

inveresk · Mar 25, 2006

6" of concrete over 1600 feet is 29.6 cubic yards. 8" is 39.5 cube. Concrete pumping would certainly reduce labour and get the stuff to where you want it and a vibrating poker would help you move it around some.

I think your solution will work as long as you finish the concrete above the highest level of the water in the basement.

Having my point of view ridiculed makes me mad but it also makes me stubborn. So I undertook a little desk exercise using your photographs. I imported one of the house and road into a CAD programme and adjusted the size so it was to scale. I then marked the approximate positions of the existing floor zone assuming a depth of 12", your crawl space, assuming a depth of 4' (base of crawl space is the red line) and an assumed position for the curtain drain on the basis that the top of it would have to be lower than the solum level if it were to reduce the water table to below it. Here I've assumed 18" lower.

I've projected the line of the curtain drain to the road and the yellow line gives a guide of where the road surface is, contiguous with the outside wall of the house on this side which is where the curtain drain would be. I've assumed that the leg of the circuit drain conducting water away from the building falls a modest 1o, the rest of the curtain drain around the foundation being level.

Given these assumptions, and the relative inaccuracies of the method I've used here, I calculate that the curtain drain would discharge at a point slightly more than 4' below the level of the road. Maybe I'm missing something but if this were the case, or even if I were out 12" or more, I can't see how it would work. This would surely be below the level of the bottom of the road ditch which must have standing water in it during at least part of the year and so, in turn, be below the water table.

Unless there's another ditch or channel you can discharge into elsewhere, the solution you propose - or a sump pump - are surely the only options?

I invite my logic to be shot down in flames but please let's keep it mannerly.

CurlyDave · Mar 25, 2006

1. You need a different Engineer.

2. I think this is a potentially very expensive problem. RFB has it right, you need to take easy, inexpensive steps to mitigate the problem and then force the builder to fix it.

Possibly we have the order reversed here -- go see a good Real Estate Attorney, and let him recommend an engineer. Someone who has dealt with construction defects previously will know the right engineers. Any attorney should give you a free hour.

As it has been noted an "as is" purchase does not absolve the builder from liability for hidden defects. This could very well be a hidden defect which only manifests itself in wet years. If you had the building inspected in a dry time and the inspector said "no big deal", all that means is that either he made a mistake, or it is only a big deal in wet years.

The bottom line is that there is a very good possibility that that he really does not "own" this problem, but that it belongs to the contractor. If I were the owner, I would be speaking with an engineer AND an attorney.

Another reason to talk to an attorney is the inspector InvestorGuy says looked at it, saw the water and said "it is no big deal". It seems to me that if the inspector was paid and if it turns out that what he said was "no big deal" is a big deal, then the inspector has liability for this. Maybe he has errors and omissions insurance, most professionals do. Anyway, another set of pockets to look into. And no issue of a warranty expiring.

I would advise against pumping concrete into the crawl space. A 7-sack mix is going to be lot stronger than the usual 4-sack mix and until you are 200% certain this is what is going to fix it, you should consider this as an irreversible step. Getting that out is going to be a long, backbreaking job if it is not the right way to go. Suppose an engineer ultimately says: "sump pump", but the place to put one is covered in 7-sack concrete...

Also, just because concrete can be pumped, it is not a self-leveling fluid when it comes out of the hose. It has a density just about twice that of water and a consistency like an underripe banana (without the peel).

You need to move the hose to distribute it, shovel it to repair the issues from not moving the hose perfectly, settle it with a vibrator, and level it with a scree board -- minimum. It would be better to float it afterwards.

I have pumped concrete, many times, and with 5 or six guys and good access to the job, 1600 sq ft would work out OK. With this kind of access it is going to be a nightmare.

inveresk · Mar 25, 2006

Investorguy, can you sling a tape in the crawl space and confirm the clear height?

Investorguy · Mar 25, 2006

@inverseek

Surely your construction kung fu is greater than mine. However, and do correct me if I'm misinterpreting, but you'r saying that is it unlikely that, due to the depths shown in the picture, draining the crawl via methods mentioned in previous posts would work due to the fact that my crawl extends too low?

I might be able to help w/ a few things. First, the footing drain (likely the downspouts too) empties into a ditch 225 feet away from the property. That would be approximately another 200 feet in back of the perspective of that picture. It empties into a ditch that does not ALWAYS have standing water. It only has standing water when it rains. However, my drain, 3-4 in corrugated pipe sticks out about a foot below the ground, emptying into that ditch. It is always running. Even when it hasn't rained for a week (which isn't often up here). That pipe stops flowing in May, which, I'm assuming, is when the water table receeds.

So, about how much per yard is 7 sack concrete?

Investorguy · Mar 25, 2006

( Investorguy, can you sling a tape in the crawl space and confirm the clear height? )

I'll try to get some more accurate measurements, including square feet, tomorrow. But it may not be until Sunday as I think my wife has my time pretty well committed tomorrow.

Investorguy · Mar 25, 2006

@CurlyDave

I have an injury lawyer who is a good client. I'll see if he can point me in the right direction as to whom a good RE lawyer may be.

I fear that I may be stuck w/ the problem though. We had it inspected, the inspector noted the water. We asked, as part of our offer, for a few grand to fix the problem. They said no, as they had 2 offers waiting in the wing, both of which were for more than ours. Given that this was the ONLY rural acreage available in our price range at the time, we felt compelled to worry about it later.

Later is now. Given the above circumstances, if i were a judge, I would probably say that I should have walked away from the house. But my father in law said that it wouldn't be too bad and it was fixable via the "fill in and raise the cripple wall" method.

As far as the concrete is concerned, I would hire that out if that ultimately becomes the solution. Not worth messing that up.

But I will talk to a lawyer next week.

I appreciate everyones paitence and willingness to offer advice, even conflicting advice.

We got my tractor out. I'm confident this problem can be fixed too.

Egon · Mar 25, 2006

Been following the thread for the last several days.

Overall situation indicates you are basically sitting on a flat area with a very high water table and a crawl space that is finished below the water table.

Yes you could use several different types of perifial pumping methods to keep the house area dry. These would require continual operation and really do not appeal to me. They are usually a sort term construction type solution.

Filling in the crawl space and capping with concrete is another method. Highly labour intensive and still leaves room for failure but seemingly the best option offered. Also requires redesign of the center wall.

Another option:
Get proper soil analyasis and then design from there using people with qualifications.

Another option may be to raise the house [ not as dificult as it may seem] Pour new walls that are much higher than the present. Backfill inside and outside the walls to well above the water table. Insulate the concrete walls and have dehumidifiers with some heat in the crawl space.

Another is to raise house, install pillings, build up an aggregate pad well above water level, poor concrete grade beams and full concrete slab to set the house on.

Then again maybe a "For Sale" sign may be the best way out.

Whatever the method used find people certified in your area for design and alteration methods.

Egon

inveresk · Mar 25, 2006

Investorguy, the only way to be sure about levels is to do a level survey which will tell you the relationship of the solum to your discharge ditch. Bear in mind that the further away the discharge point is from the house, the deeper the drain is going to be at the outfall because it will need to have some sort of modest fall. At 225 feet, a 1 : 60 fall will mean a slope of 3.75 feet. If the circuit drain starts off, say, 1 feet below your solum and has to drop a further 3 feet plus, where is the discharge ditch in relation to this level? If your land is pretty flat, this may be well below the sole of the ditch.

Curlydave is right about the mix. You just need a lean mix here, not high strength. You could also order a wetter slump than normal which will help it self level some and you could ask for a retarder to be included so you have more time to work it. Last thing you want here is to have a load of concrete go off on you in the crawl space before you've levelled it. I think to do this job in a day is pushing it.

Point of information - my crawl space has a concrete slab and about 3'6" clearance. If I remove the slab and dig down a bit, I'd end up with your situation. Slabs in the crawl space are mandatory here because of earthquate risk. They're mandatory in the UK where they're normally finished with a couple coats of cold bituminous solution to help waterproof them. There's no risk of the slab having to come out if you were to add it. However, the one thing you don't want to do is to pour a slab then find the top is still below the water table and you haven't solved the problem so you need to be sure just how much concrete to add. This is not a job you want to do twice.