Basement Moisture & Installing A French Drain
The house that I am closing on next week has some water damage and mold in one corner of the basement. The home inspector advised that we install french drains in that area to help this problem. The drain needs to be about 8 feet deep. Any advice on how to do this? How do I make sure the drain will not collapse under the pressure being at 8' below? I also need to seal that concrete block. Any good methods or products? Thanks in advance for any advice.
[addsig]
What they do is take a backhoe, and dig right down beside the foundation of the house, put the pipe in it, and put gravel on top of it, then bury it. Also, while they've got the dirt moved, they put like polyurethane (plastic sheet) against the outside of the blocks. It's kinda pricey to have this done. I had a water problem in a basement once and solved it by piling topsoil up against the base of the house to turn the water away, and installing guttering, with a drain to drain the water away, then I sealed the inside of the basement wall with Dri Lok,(get it at Home Depot, or any building supply place) a thick paint kinda substance, but the wall's gotta be dry when you install it, or it won't work. You might want to get a contractor out that specializes in sealing basements, and get their opinions...
Good luck!
The other technique is to do it from the inside. You cut out the concrete floor around the interior walls in the basement, install the drain pipes and have them lead to a sump pump.
Installing french drains around the perimeter on the outside of the basement at the basement floor level means the water has to get back up to the surface to drain away or you better have a walk out basement where the pipes can use gravity.
As stated above the cheapest fix first would be to see if there is a gutter and surface drainage problem around the outside of the house. That will be the very cheapest fix before you are forced into an expensive french drain fix.
Read this article from NCYank first.
http://www.thecreativeinvestor.com/modules.php?name=News&file=article&articleid=492
Hi Laura,
There are basically three ways french drains are installed,(1) interior french drains (which are a total waste and unhealthy) (2)exterior french drains (up against the house, laying on the footer) and (3)exterior french drain placed away from the house, as much as 10 feet or more, designed to catch water draining from steep grade / incline before it gets to the house.
The third method is the cheapest but may not apply to you, it is best to speak with several professional companies that specialize in this field. Make sure they offer a warranty of at least 10 years or more. Check references and ensure they carry sufficient workers comp. and general liability insurance as well.
Initially I would look at addressing the existing grade and guttering of the house and try an interior sealer at first, however if this does not work then be prepared to fork out some greenbacks.
NC_Yank
PS. In instances where the water table (ground water) rises INFREQUENTLY.....a sump pump can be employed. This happened last year in the Carolinas.
The problem with relying on sump pumps for continual / on going moisture problems is that all the moisture that collects under your crawl or basement will eventually effect the structure / footers of your house.
Recently I was speaking with my insurance agent about reoccuring foundation problems that were due to the rise in the water table, she informed me that the majority of those claims will not be honored. Its like flood insurance.....unless you have a rider policy chances are you are out of luck.
Bottom line is that any and all moisture problems need to be addressed.
Good luck
NC_Yank[ Edited by NC_Yank on Date 03/28/2004 ]
NCYank,
You mention what to do if the water table is low. But what do you do if it is high? I'm looking at a property that sits on low ground next to a creek. The creek never overflows(the house is basically located a few feet down from where a large spring comes out of a hill side), bet the ground is only about 1 ft. above the water level. I assume that the ground water table is only 1 ft down also since the creek has never run dry. The house is 50 years old and doesn't have any visible damage, but it is obviously very moist in the crawlspace. Do you just cover the ground well with a thick plastic?
Quote:
On 2004-03-28 14:24, davmille wrote:
NCYank,
You mention what to do if the water table is low. But what do you do if it is high? I'm looking at a property that sits on low ground next to a creek. The creek never overflows(the house is basically located a few feet down from where a large spring comes out of a hill side), bet the ground is only about 1 ft. above the water level. I assume that the ground water table is only 1 ft down also since the creek has never run dry. The house is 50 years old and doesn't have any visible damage, but it is obviously very moist in the crawlspace. Do you just cover the ground well with a thick plastic?
When you have a constant high water table, then you need to completely seal the crawl space. In the event where you have great amounts of water coming in....then I would employ an interior french drain, HOWEVER I would still seal the crawl space by putting down a thick, up to 50mm cover on the ground, around any piers, up the foundation walls and taping and sealing the crawl space so that it is air tight. In some cases you can even put a dehumidifier in place as well as conditioning / controlling the temperature of the crawl space.
Get a hygrometer (check humidity levels) and annotate the readings you get to determine if there is a problem and what patterns there are if any...
The key is to give the crawl space an air tight seal.....even closing off those ridiculous foundation vents that allow humid air into the crawl.
I recently wrote an article about the "stack effect" that comes with crawl spaces........I suggest you read it and any follow up that I gave.
I love crawl spaces but they can be problematic in areas with high water tables.
Let me know if I can answer any more of your questions.
NC_Yank[ Edited by NC_Yank on Date 03/29/2004 ]
one product i have had sucess with is zypex, mixes with water, then you spread it quickly with a rubber glove, its cristaline in properties and grows in to the concrete, great sealer, many hard ware stores have it
John
NC-Yank,
Thanks for the info. One other question comes to mind though. You mention taping the plastic or other material you put in the crawlspace. Are you using a certain type of tape for the plastic seams and another type to attach the plastic to the foundation? I read one place about using polyurethane caulk, but I think I would have to take out a loan to buy enough of that stuff to do all the seams and around the crawlspace walls. Also, while I'm thinking of it, what have you found to be the most convenient width of material to use? I'm not sure if there is a common distance between piers under most houses that would make it easier to use a certain width roll, or if it's better to just get the widest stuff possible and start cutting and splicing.
Building in the Hills of Hollywood exposes you to many and wonderous solutions to all kinds of problems.
If I am first in line and build the house I always install the drain french with the little holes and stuff right up against the upoutside of the retaining wall or foundation line. I also make damn sure that each end of the drain reaches past the line of the dwelling and is then connected to solid pipe that drops at least 1/4 inch to the foot. All of which is laid in a layer of small rock which is then covered with great care. Thus the water coming down the hill if it gets below soil level it runs into la drain french who slurps it up through its little holes and carries it along either side of the dwelling and down to the street of record. Sometimes I have a ground drain line installed usualy a 5 inch or on some occasions 6 inch pipe.
Now that takes care of the under soil stuff. If I am up against a foundation line I have lined the entire back with plastic and it is attached to the foundation line with a gunky black stuff very similar to 208 of roofing fame. Seems to work. No problems over the last 20 years.
Of course when I am not first in line and I come in after another builder whose basic concepts of construction are learned in nomadic structures resembling Yurts, then I have a problem. I cannot begin to describe the various events we have viewed. The basement which resembled a large swiming pool. Seems the entire hillside was discharging water into it by virtue of a small hole the original builder left in the foundation line. Said something about a vent stack er something.
My new all steel container houses are of course 22 inches above grade. In some instances I may go higher to 24 inches. Yes I have gained some weight . In one of the applications on a slight upslope lot we are pouring a slab at 4" under where the house will sit on its little concrete pilings. The plumber and electrition will slide to work on those little sliding trays that mechanics use under cars. There is even a lighting system so you can see everything. Yes you can tell the houses erected by ex plumbers.
I hope this is of help. Lucius
"On 2004-03-29 23:11, davmille wrote:
NC-Yank,
Thanks for the info. One other question comes to mind though. You mention taping the plastic or other material you put in the crawlspace. Are you using a certain type of tape for the plastic seams and another type to attach the plastic to the foundation?"
NC: tyvek tape will work fine.
"I read one place about using polyurethane caulk, but I think I would have to take out a loan to buy enough of that stuff to do all the seams and around the crawlspace walls."
NC: It is pricey because the manufacturer knows it works. Give up a few candy bars for awhile (smile) and put it toward the caulk.
" Also, while I'm thinking of it, what have you found to be the most convenient width of material to use? I'm not sure if there is a common distance between piers under most houses that would make it easier to use a certain width roll, or if it's better to just get the widest stuff possible and start cutting and splicing."
NC: Use what is most economical as well as efficient at laying it down. There is know need to get the largest width roll if you are going to have to cut it anyway.
I am listing a few site that you can read and see what I am talking about....especially the various methods.
The site below is conducting tests here in North Carolina......as far as I can tell they have not released the final results.
At anyrate the method and principals to work....you just have to evaluate for yourself what would be best for your situation.
You can do a google search about sealing crawlspaces and basements to find a reputable company in your area.
NC_Yank.
http://www.advancedenergy.org/buildings/knowledge_library/crawl_spaces/field_test/homes_and_experiment_setup.pdf
http://www.advancedenergy.org/buildings/knowledge_library/mold_and_moisture/crawl_space_rain.html
I have had great success in connecting the drain to the existing sewer. When the sewer line is under the concrete( if you have a cement floor it is fairly easy to cut out a drain and expose the pipe and tie your drain into it. IF not I put in a sewer ejector and use the sewer main that way. Costs a few hundred if you do it yourself. French drains are ok in certain conditions but still leave the water in the soil and under the house. IF the water table is say, 2' below the crawlspace then I don't care if you have a 10' drain hole it will not drop below 2'.
In bentonite/sandy soil frenchies work well in basement cralspace areas.[ Edited by Stockpro99 on Date 03/31/2004 ]
NC Yank- curious why you consider interior french drain systems a total waste and especially why you consider them unhealthy?
This is pretty standard method of correcting foundation issues caused by bentonite soil and water issues here in Colorado, companies are installing this system everyday and codes is signing off on them without any problems. Engineering firms are also useing this type of remedy in their proposals to homeowners as the second condition along with foundation jacks to bedrock to fix houses permanently that have movement problems due to expansive soils coming into contact with water. Warranty companies are also inspecting and accepting this a a viable solution.
I have also never heard of any health issues, even if you are talking about radon coming out of the sump well, they can cap these to eliminate that. I can't imagine what health issues there are. A gallon of water sitting at the bottom of your sump well?[ Edited by The-Rehabinator on Date 03/31/2004 ]
It will be interesting to see what NC_Yank's answer is to the question above about interior French drains. It does seem that it would be much easier to install one on the exterior obviously, and it seems like it would accomplish the same thing. A drain on the interior still has to draw water from everywhere under the house, so it seems like pulling down the water level just outside of the foundation wall would have the same effect. How could you have a low water level at the foundation wall, and have a high water level just inside?
Hi Rehab......
You can check out the article I wrote and is posted here in TCI........but I will try to condense it for everyone here.
Houses to in fact breath as we all know....when warm air rises then it is replaced by air from somewhere......guess where it is coming from......in all likelihood your basement or crawl space. It is called the "stack effect".
Think of it in terms when you start up a wood fire place....you open up the damper in order to "draw" air into the flue in order to get the fire going.
Same thing happens with a house. No matter how much insulation you put in your your floors....they are not air tight.
This is evident by the expansion and contraction of wood floors.
There are methods that can get fairly close to achieving this but few builders do this because of cost.
Only in cases where you have a high water table....would I recommend a french drain. In most cases the problem needs to be addressed where it is happening at............the outside.
Yes, I know that most rehabbers will not address such issue......which is fine.....however the problem will not go away by simply ignoring it......it is often passed on to the new unsuspecting buyer.
Imagine you call me and say your roof is leaking.....I bring a bucket over, collect the water and dump it out.........and of course charge you for it........you would kick me in the butt and throw me and my bucket out the door. This is what interior french drains do..............the moisture is still in the air. High moisture content is what is needed in order for mold, mildew, termites and other bacteria and spores that you can suck into your lungs and enjoy. If I am going to live a house with such problems, I think it is to my advantage to fix it permanently.
Do I think that every house should be completely sealed........No.......but if you have a smelly, musty, mildew crawl or basement then you are likely breathing it.
As to code officials, many I have come across have very little experience in building.......they learn to look for about dozen or so common problems and move onto the next job.
Engineers.......I love engineers, ............(at least more than architects) I use them frequently to check my designs and recommend them for certain issues on home inspections................but lets face it.....they are often called upon when something goes wrong....they then tell you why it failed and come up with a solution to fix it.
Let us also remember engineering encompasses a large field....dont look for a structural engineer to address a bio-health problem.
And now since we are speaking of health......it time for a healthy bowl of ice cream........cheers all.
NC_Yank
Quote:
On 2004-03-31 10:11, davmille wrote:
........How could you have a low water level at the foundation wall, and have a high water level just inside?
The majority of water coming in from foundation walls is a result the improper sealing of the exterior foundation wall as well as improper grading on the outside of the house........a high water table is typcially God's work......and since He created this planet and is the owner of same.....He can do with it as he pleases. (smile)
I do remember Him telling us about building our houses on a "firm foundation".......if we don't listen....as was the case with Adam & Eve.......then whoa unto us.
.....back to my ice cream......
NC_Yank
I can understand now a little bit why you would have your opinion, however your case doesn't apply everywhere.
Drainage here in the west is to prevent expansive soils from coming into contact with water to prevent foundation movement and water in the basement. Moisture and humidity don't enter into the equation. There is little to no moisture or humidity here. In fact people install humidifiers to their central air systems to inject moisture into the air here.
In your case you are seeing any moisture in the house as a problem. However I would really have to be convinced with some hard evidence that there is a difference in an interior or exterior drain system even in your part of the country. All the water orginates from outside the house, the only difference between an exterior or interior drain in on the interior system the water moves 12 inches or so from the outside, under the foundation wall, into a drain tile and is then pumped out of the house. The floor where the drain tile has been installed has been repored and sealed so there is no pools of water sitting under the basement floor or anywhere else.
Regardless, I understand your perspective on the situation based upon your local conditions as compared to ours.
Out here if the basement is unfinished space it can be cheaper, less intrusive and more effective to install the interior system, then getting back hoes into place, destroying landscaping and digging down 8-11 feet to install an exterior drain tile around the perimeter of the house, especially when you take into consideration driveways, sidewalks, existing decks and pools.
Afternoon Rehab,
I look at it as a case by case basis regardless as to what part of the country you are in.................all one has to do is get a cheap hygrometer (about $15.00 or less) and periodically check the humidity levels in their crawl space or basement.
If the readings are consisitently over 50% - 60% AND it is effecting the crawl spacel / basement (mildew, mold, etc), then it needs to be addressed. The solution is to get rid of the moisture in the most economical, practical and permanent means as possible. The only solution may be an interior drain.....however this is often done because of cost.
I have seen interior french drains installed......typically for about 20% - 40% of the cost of an exterior drain......but I also can note that with the majority of these interior drains you still have very high levels of humidity in the area in quesiton.
My intentions are not to scare people that have crawl spaces / basements.......its to educate them with my findings and experiences that I have observed in various places I have built.
At anyrate, any untrained person can look for mildew and notice the smells.......if they are there then they should address it.
NC
This stuff sounds alot better than using a standard French drain and the price seemed very reasonable when I called about it. I haven't tried it yet, but I think I'll give it a try on a house I'm closing on. Maybe someone here has used it or has heard about it.
http://www.varicore.com/index.html