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

[Investorguy]

Okay, we bought our house just about a year ago. It was built about a year before that. It was perfect when we got it, except for a good 3-4 inches of water all around the crawl space. House is still new so there was no mold. However, vapor barrier is not meant to float on top of water, so something has to be done.

There are a few important details to consider.

*I'm in a very wet area. See this thread for more details. As an example, if I go walk out in my field, even 30 feet away from my house, I'm not walking in standing water, but you squish with each step like you're walking on a sponge. If you listen, you can literally hear the water running over the surface of the land.

*I have a 5 foot crawl space. At least that much. It's more like a "walk-hunched-over space". So it'd be very easy to get work done in there.

*The 3-4 inches of water is about 2-3 inches from any wood. You can see the highest the lines go when it's dry; there's not danger of the water actually touching the wood.

*The water level appears to stay pretty constant throughout the wet season. Doesn’t really go up or down. Its pretty much either there or it’s dry. It dries out in about May I think and gets wet in November.


I have no visible mold yet, but I need to get this taken care of permanently this summer. I’m not all that handy (but I’m working on it) with tools and such, but I’m good enough at making people money on their investment portfolios that afford to pay people who are much better at this stuff than me. Clearly I want to keep costs to a minimum, but it’s much more important to get the job done right.

I’ve had these solutions presented to me:

1. Pea-gravel. My father-in-law is a pretty handy guy w/ contracting experience. He suggested I blow out a foundation vent and put a spread 3 inches of pea gravel all around. This won’t do anything to the water, but it will allow the vapor barrier to sit on something solid instead of floating on water. He seems to think that would allow the vapor barrier to do its job and the problem would be effectively solved. Sounds pretty simple. Almost too simple.

2. I talked to a guy who dug some drainage ditches for me last fall. He supposedly was an expert in this field (even though I caught him putting the berm on the wrong side of my ditch). He said he’d solved numerous water problems and would solve mine the same way. He would dig a small trench around the inner perimeter of my crawl space, then do the perforated pipe thing w/ rocks and gravel and send it out to the road or connect into my footing drain pipe. I am skeptical of this fix b/c I think the foundation was simply dug beneath the water table. The footing drain pipe runs constantly all wet season. I think they may have put the footing drain too high, but that’s another story. Anyway, I asked him if he would guarantee that it worked. I haven’t heard back from him on that.

3. The most interesting solution appear to be one suggested by a crusty old guy that goes to my church and seems to know something about everything. I love people like that; I hope to be one when I’m old and crusty. Anyway, he said that I need to “7-sack” waterproof cement and get a truck to pump a floor into my crawl space. He says if I get a few inches of that all around then the water won’t be able to come up and the problem will be solved. I really don’t know much about working w/ concrete, but it seems like this is promising. I wonder a bit if the new cement will create a waterproof bond with the old footings? I know that putting some really heavy rock on land will squish the water out and away to areas. This stuff should be pretty heavy. However, if it doesn’t work, then it’ll be REALLY hard to drain the crawl space. Also, wouldn’t I need to put down crushed rock or something first? Or will I need rebar or some kind of wire mesh? The floor won’t be carrying any kind of weight from above, but the water will be pushing on it from below.

So there is my predicament. I want to get things rolling to get this all lined up to permanently deal with this summer, so I thought I’d throw it out to the most knowledgeable group of folk I’ve met yet on the internet.

Thanks for reading!

 

[CurlyDave]

You might not like this response a lot, but you really need to get an engineer out there to take a look.

I have a 5 foot crawl space. At least that much. It's more like a "walk-hunched-over space". So it'd be very easy to get work done in there.

The problem is not doing work in the crawl space, the problem is doing the right work in the crawl space.

It is going to be a whole lot easier to put things into the crawl space and spread them around than it is going to be to get that same stuff back out if it is the wrong thing.

From your point #2, you clearly have existing drainage ditches and a footing drain. Does the footing drain work by gravity, or is there a sump pump?

I am an engineer, who built his own house (with my own two hands) and somehow I suspect that the real answer to this problem is going to involve a french drain around the outside of your foundation, with either gravity drain to a lower point, or a sump pump, lots of drain rock (either pea gravel, +3/4 -1 1/2", 1" drain rock, or 2" drain rock) depending on what is most cost effective locally. All will do pretty much the same job. A vapor barrier, a couple of inches of sand on top of the vapor barrier and then re-bar and 6 or 7 sack concrete, pumped into the crawl space. Do not allow anyone to tell you that the 6-6-10 wire mesh is as good as rebar. It might be in theory, but every job I have ever seen done with it promptly cracked, whereas every job done with the right amount of rebar has not cracked.

Perforations in the vapor barrier from existing piers would have to be dealt with in some manner, and I just don't know what the best local practice is.

If this sounds expensive, that is because it is going to be.

What I can't tell without looking at it is where to drain this all to, and whether or not a sump pump in your crawl space will be necessary.

You do not want to take a chance on getting black mold. I have read about houses which had to be abandoned because of mold, and insurance companies do not cover this any more.

After you get an engineer's report and an estimate for all the work you can decide what to do. You may have a claim aganst the original builder, or the seller due to an undisclosed defect.

Anyway, if you pour concrete in there before you have put the proper material underneath it, you will have a very difficult time getting it out.

On the grand scale of things, I think I would rather have my mother-in-law move in with us than have to fix a slab poured without the right material beneath it in a 5 foot crawl space. Which is going to be closer to a 4 foot crawl space after all is said & done.

Another reason for getting an engineeer: If you pour concrete in the crawl space and do manage to make it watertight against the footings and the piers, you will have constructed something which looks a lot like a swimming pool. I have owned real estate off and on, and once had an apartment building where the building inspector convinced the manager that the markings on the bottom of the swimming pool had to be re-painted. The idiot manager drained the pool in the middle of the rainy season, and it floated up about 6-8 inches. This tore up all of the plumbing, and busted up the concrete. We ended up abandoning the pool and filling it with sand.

Imagine the havoc if your newly-constructed, very watertight basement floats up a few inches in the next wet season.

 

[Investorguy]

Thanks Dave. I guess no on else is up at this hour.

The current footing drains just work by gravity. I've been told to avoid solutions that involve a sump pump.

A few people have suggested that the footing drains were improperly placed, too high on the footings, thus allowing water to get under them. Maybe. I think that the water table is just too high. The crawl space was just dug deep that it should have been dug.

What kind of engineer should I talk to? I've talked to tons of people and I've gotten just as many VERY different opinions.

Although there is a slight downward grade from my house to the ditch out by the road, I don't think that the water will be able to be drained out of the crawl space due to the water table issues. I think that's just where the water is. I think the solution will involved filling in with something.

And I agree, the last thing I want is "floating basement" floor.

I'll be sure to use rebar if that's the proposed solution. Another guy told me to use 7 sack concrete and not let them talk me into 6 sack b/c it's not as waterproof.

Dave, given what I've told you about the likely height of the water table, do you think that french drains of any time would likely have the desired effect, whether or not the footing drains were done right?

 

[Paddy]

InvesterGuy,

I'll bet you have had enough of the rain by now with your tractor stuck and now the crawl issue.

The situation is not good but a few points. If you are below the water table, you will never be able to drain it. But if you have an area within a few hundred feet that is lower than the bottom of your crawl, a drain would work.

Is the plastic completely dry on top?? If yes, it's working. Way back in my construction days before I became an eninerd, I came upon a house with the same story. I was asked to go down for some other reason. There was 4-6" of water under the heavy platic. Dry on top!
The plastic will be fine untill the first hole appears. So I wouldn't travel to much on it if it's working and good conditions.

As far as to the house floating: The pool floating is like a soup bowl floating inside another soup bowl.

 

[EddieWalker]

Investorguy,

From you previous post about your tractor being stuck and now the water issues at your house, it sounds like your living in a very low area. Maybe bordering on a swamp.

No point worrying about what the builder of your house did wrong or should have done. That list will just keep growning and what's done is done.

Putting rock or cement in your crawlspace wont address your problem.

Your problem is water is gettng to your house. You must first address this by stoping the water and sending it away. The people you talked to should have told you this.

There are a few different ways to do this, but the first and most important is that you need a SLOPE AWAY from your house. Just a few degrees will work. Lets say 5 degrees to keep it simple.

Now this is gonna take some effort with a tractor to remove the dirt and relocat it someplace. It will also destroy your landscaping and lawn. How far away from the house you go is up to you, but I'd think ten feet would be about the minimum. 20 feet woudl be even better. At ten feet, you need a to be at least 6 inched deeper than your foundation. At twenty feet, you need to be one foot deep.

Next you need to create the slope back up and away from teh house. The more gently you make it, the slower the water will flow and the more apealing it will be to the eye. It will also be that much more dirt.

Once you've created the minimal drainage AWAY from your house, you can address how to get rid of the water. What you've accomplished so far is to put your home on a dry island and surround it with a mote. House is dry and the water needs a path to go away.

You can either keep digging a very wide shallow channel away from you house to drain the water, or you can trench in some drain pipes.

I think you don't have any options on creating the drainage away from your house, but getting rid of the water gives you a few choices depending on your area. How much dirt would you have to remove versus how long the drain pipe would have to be??? Both have their pro's and con's.

I thought about a french drain around your entire house close to the foundation, but don't really like this as much as digging away the dirt to create drainage. A french drain would have to be right next to your foundation, which means digging around your entire foundation. I'd prefer not to do that. You could put it further away, but you still have to slope the land away from your house to the drain to keep water out of your crawl space. The french drain would have to be deeper than a five degree slope, requireing deeper trenching to lay pipe to remove the water, and it would have to be all pipe until you got to a low spot. This could all add up to allot of money.

Open drainage is just a low area around your home that is covered with lawn that you mow like any other lawn, but it's also keeping the water away from your home. No upkeep or repairs besides mowing. Very simple and effective. It's my prefered way to do things.

After you get the water draining away from your home, than you can lay some pea gravel over your vapor barrier if you like, but I'd wait until it got all nice and dry under there first. I might even pulle the vapor barrier out for awhile to ensure it dries out. All moisture is bad in a house, so you don't want it to be kept under the barrier if you can help it.

Good luck,
Eddie

 

[jeffinsgf]

Just to clarify things a little, from a couple of things you mentioned in your posts, it sounds like your perimeter drain is above the grade level in your crawl space. Is that right? If so, and the house is a couple of years old, I would start following the advice to contact a construction engineer with experience in your area. The next person I would contact is a lawyer. I am not by nature a person who turns to legal action to solve problems, but if the builder put the perimeter drain above the crawl space grade level, he needs to called to account for his actions. The perimeter drain should be sitting on top of the footing -- absolutely no higher.

I am not an engineer, but I have built a few homes, a few commercial buildings and lots of pole barns and other ag buildings. I don't think adding gravel is going to solve the problem. You need a drain below the level of the crawl space grade that runs down hill to daylight.

If you are having trouble finding the right engineer to contact, start with a home inspection company. A home inspector can judge just how serious a problem you have and direct you to some experienced local help. In Missouri, home inspections are optional in a sale. I am really glad that we sprang for the extra expense. Got a few things fixed by the seller and got a lot of peace of mind.

 

[CurlyDave]

I think jeffinsgf has a good idea to start with a house inspector. This is a $200 to $300 cost around here, and a good inspector will be able to point you toward the right engineer.

Otherwise, look for: Foundation Engineer or Geotechnical (Soils) Engineer. When I built my house I had the plans drawn by an Architectural Engineer (maybe he was an Architect, I am not certain of the difference) who required that I also hire a Soils (Geotechnical) Engineer to be certain he got the drainage and soil load bearing capability right. I took his design, doubled the foundation bearing area and trippled the amount of re-bar he wanted. In 15 years we have had no water problems and no settling. I am in a hilly area so drainage is not an issue.

If you have a gravity drain to a lower point you may be able to get a solution, but from your description of the property and the wetness everywhere you may be in a low lying area.

The thing I find worrisome is that your house is only two years old and already you can see high-water marks in the crawl space. While they may be low enouigh to live with now, and this may have been a wet year, it is nothing like the wettest year on record.

The house has to be able to take the wettest conditions it is going to see for the next 50-100 years, and somewhere in there it will get a lot worse than this year.

I've been told to avoid solutions that involve a sump pump.

This is good general advice, and I agreee with it. Sometimes there gets to be an "as built" condition where a sump pump is the most economical solution, especially if there is not sufficient natural grade.

As much as I respect EddieWalker and agree with him that you need a slope away from your house, the solution of lowering the grade level around the house may not be the one you want. If the water table is high enough, you may just create a moat around the house, which will not solve the problem and may make it worse.

Get a professional to look at it. The real solution may have been to import material at the time of construction and raise the level of the house.

I would really start keeping records of everything you do. Water like you describe is a serious and potentially very expensive problem. If an engineer thinks there is something you can do on your own which will resolve it for a few thousand $, go for it. But, you may be talking $10k to $100k for a permanent fix and if it should ever happen to come down to a legal issue, the opposing team is going to claim that any remedy you tried on your own without licensed & registered professional design made things worse rather than better and therefore the liability is yours.

Eddie says: A french drain would have to be right next to your foundation, which means digging around your entire foundation. I'd prefer not to do that.

I don't like the digging part either, but I have done it before, and it was successful. I got ready for the job ahead of time, waited for a dry part of summer, and dug in short sections, which I lined with landscape cloth and then backfilled as I went along. Didn't have a tractor & backhoe at that point, so it was done by day laborers with shovels and an electric jackhammer with a clay spade. This is a very cost-effective, and safe method of trenching around an existing structure. The day laborers were $10 an hour and they did 80' of trench 3' deep in either one or two days. I think it was one, but that was 5 or 6 years ago. That included backfilling with drain rock.

 

[RFB]

I think that Dave has given you sound advice, and without putting words into his mouth, you have a potentially serious problem that may not be financially practical to solve.

Pumps and grading are all predicated on finding a way to move the water far enough from your house so that it does not replenish the existing supply. Just moving the water into the "reservoir" that is feeding your crawl space is no solution. If you are in a depression with no natural drainage, you have a substantive problem. (Think New Orleans)

Dave's point about the costs/effort required to unfix a bad fix is a fix you do not want to get into.

Keep your mind open to the possibility that there may be no cost effective remedy.

 

[Highbeam]

"Although there is a slight downward grade from my house to the ditch out by the road, I don't think that the water will be able to be drained out of the crawl space due to the water table issues. I think that's just where the water is. I think the solution will involved filling in with something.

Dave, given what I've told you about the likely height of the water table, do you think that french drains of any time would likely have the desired effect, whether or not the footing drains were done right?"

You can lower the water table around the house with proper drainage below the elevation of the desired water surface. The water will constantly run so long as the surrounding water table is higher than the pipe as it should. In the same way, a sump pump would constantly pump to keep the water table down below the surrounding soil. The flow rate of the pump or gravity drain will depend on the type of soil and how fast water moves through it. Usually, swamps have clay and water doesn't move too quickly through it so a sump pump with a substantial reservoir isn't out of the question. Gravity is always better though so long as you have a dependable lower area to drain it. Realize that without some sort of check valve, the water from the ditch could back up into your crawl space.

Eddie hit on an important point. The first thing you do is be sure that your downspouts and the grade of the ground aren't sending water towards your foundation. Unless you are built into a hole, you can grade away from your house. Our building codes require that.

Then your footing drain must be deep enough to drain the water to the desired level which is below your crawlspace floor. Here's the question, when in your crawl space can you see the whole footing, the wide concrete strip below the stem wall? The builder may not have backfilled inside the crawl at all and the footing drain is resting on top of the footing. Leaving you with an undrained depth between the top of the footing and the earth. Worse yet, he may have plumbed your downspouts into the footing drain which effectively pumps the roof water into the footing drain and then around your foundation.

Several builders here in the valley have begun using gravel fill in the crawlspaces. It is a fine way to hide the water and the vapor barrier will still be effective at stopping the water vapor. The vapor barrier is not supposed to seal water out. It can have some holes in it and overlapping seams without glue. It is only to stop steam.

I would not pour concrete at all. No good reason that I can see for that.

First make sure the sirface drainage is not adding to the problem, and then lower the water table around your home with proper drainage ideally by gravity. After that, you can mess with gravel if you still see the need.

I assume that when you say you have a 5 foot crawl and the wood is still 2 inches from the water that you have some sort of support posts or something rather that 4'10" of water.

All the engineer types described above (architectural, soils, foundation, geotechnical, hydraulic, etc.) are civil engineers. The architectural one is an oddball, he wouldn't know which scale to use.

 

[Investorguy]

I'll take some pictures of my house today. It was built up on a mound of fill.

I'll also take some high res pics of the crawl space w/ a flash to give you guys a better idea.

I really do appreciate all your advice on this. I'm not willing to believe that there's not a solution. It may be an expensive solution.

One thing I've started doing is NOT putting in those styrafoam foundation vent blockers. I pay a higher heat bill, but I keep plenty of ventilation all year round.

I'm not sure about the footings. I'll take some pictures today. It will be apparent I'm sure. The vapor barrier is mostly dry, except for a few areas where I've stepped on it. That would be one benefit to the pea gravel solution; the barrier would have something to sit on if I need to go down there (which isn't all that often).

Am I guaranteed to get mold under there unless I COMPLETELY drain the crawl space? Will the vapor barrier combined w/ foundation vents prevent mold? There is zero evidence of any mold so far and looked pretty hard last summer.