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Brand new house...but basement VERY humid

Posted by nadine33 (My Page) on
Mon, Aug 20, 12 at 14:35

WE just moved into our new construction house the end of April. Shortly after we moved in we noticed that the basement felt very humid. We put some of our cardboard moving boxes down there and after a few weeks we were down there and they almost felt damp to the touch..you could feel the moisture in them. We mentioned it to the builder (we have a 1 year warranty) but he didn't think there was a problem. We have a dehumidifier that we run constantly. Because we don't have a drain, we need to manually empty it. We empty it every morning before work and it is full (and shut off) when we get home. On the weekends we can empty it (from full and shut off) at least 3-4 times per day. I don't have an exact listing, but I think it holds about 1 gallon of water. Yesterday I decided to move some things around and found a couple bags with mold growth on them. They did not have mold when we moved them less then 4 months ago. I contacted the builder and am waiting to hear back. Does anyone have any input on what we should do? I'm debating on contacting a professional myself and see what they say and then let the builder know. I also thought about getting a 2nd dehumidifier. The sq ft of the basement is approx. 1300. We do not have gutters and noticed that we have a "trench" around the perimeter of the house from where the rain falls. We also had some water in the basement during our walk-through that appeared to come from the bulkhead, but that was fixed.


Follow-Up Postings:

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RE: Brand new house...but basement VERY humid

No gutters? That's a problem because you want to get water away from the foundation. Adding gutters would be where I would start.


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RE: Brand new house...but basement VERY humid

No drain whatsoever? Do you have a sump pump? If you have no sump pump, you have no drain tile around the foundation.
You may have ground water with no way to eject.
Get after the builder NOW, while you still have a warranty.
Warranty - HA! - that's an entirely 'nother subject.
Experience shows a builder will stall until you have no recourse.


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RE: Brand new house...but basement VERY humid

You have two issues. The first in bulk water, in your case very likely the result of no gutters. It's hard to believe that's allowed in new construction anywhere! I didn't have gutters on cottages built on stilts on bedrock. Different matter.

The second is vapour diffusion, which you can't avoid and the builder evidently didn't take any measures to reduce and isn't required to.

There are approximately 300 pounds of water per one cubic yard of concrete. As your new slab and walls cure, that water has to go somewhere. As well, unless there is a sub-slab vapour retarder, moisture from the soil will be forever infiltrating, as will moisture through the walls. As well, in the summer, moisture will be drawn through the above grade sections of your basement. The hotter and more humid your environment, the more moisture you will have in your basement.

The relative humidity in your basement should be below 50% to deter moisture problems. You need a hygrometer to accurately measure it. If one dehumidifier doesn't do the job, get another one. (I run two units 24/7 in the summer--in a 50-year old house with no moisture retarders anywhere in the basement.)

Do NOT attempt to dry your basement by keeping the windows open. This just brings in more humid air. Do not store cardboard boxes on the floor. We have a lot of storage in our basement; I just knocked together 2x2s under OBS, which also saves us on the occasional minor flooding.

Here is a link that might be useful: Investigating and Diagnosing Moisture Problems


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RE: Brand new house...but basement VERY humid

There are 14 houses in this new development and none come with gutters. We are thinking about installing some, but haven't gotten any quotes yet.
We don't have a drain in the floor anywhere and I dont think we have a sump pump (not sure how to tell, but there isn't anything I can see).
We were hoping to finish the basement in the future (not for a few years..but down the road). I don't know exactly what the warranty covers, I'll have to look that up. I haven't heard any of the neighbors complaining about basement problems but maybe I'll have to ask around. Ours was the only one built this winter (foundation poured in January) and I know they used some sort of additive to help with it curing.
ANyone have an estimate of how much it costs to add a drain/sump pump?


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RE: Brand new house...but basement VERY humid

Here's a quote from our warranty. SOunds to me like we're on the hook if it's condensation???:

"We Warrant that the concrete foundation and floor will be free form seepage and leakage and surface water for a period of one year from teh closing date. However, it is impossible to assure you that condensation will not occur as this is the nature of new concrete, and therefore, we expressly do not guarantee against dampness by reason of condensation. Moreover, it is the homeowners responsability to correct any minor settlemet near the foundation, which may cause water pockets. Not covered by this warranty is seepage due to unusual flooding or rains greater than two inches in 24 hours. IN the event that it is required to correct a seepage problem, the same will be corrected at sellers expense by the installation of a perimeter drain and or pump at the sellers discretion. IT is not possible to prevent concrete from minor cracking because of the nature of the material. All major cracks that emit water are covered for 1 year from date of closing."


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RE: Brand new house...but basement VERY humid

Ditto mike kaiser - Don't know in what part of the country you are, but first I think you need gutters and downspouts, for sure. Opt for the largest, you won't be sorry, 4" standard are just too wimpy. Next, be sure your grade is sloping away from the foundation and channel rain runoff away from the house for several feet with some kind of pipe, pvc, extra gutter pieces, etc., whatever works. If the slope is good you can bury it almost up to the end. Big box stores have all kinds of solutions to deal with the drain ends, little grates, popups,
etc. so you don't run over with lawn mower.
As far as drain tiles and sump pump and/or ejector pump, you need to get estimates. It's not cheap, perimeter of the foundation would have to be dug up, and a sump pit installed, but in the long run will save you headaches and heartaches.
It might not be a code issue in your area, but I still would be outraged at the builder.


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RE: Brand new house...but basement VERY humid

Rushing to spend thousands of dollars for excavating, waterproofing, drains and sumps is a mistake when all you have may be nothing more than normal condensation and moisture laden air.

Getting the bulk water away from around the foundation is a necessity though.


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RE: Brand new house...but basement VERY humid

Thanks all,

We're going to get estimates for gutters and also buy a 2nd dehumidifier for now and see how it goes I guess...


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RE: Brand new house...but basement VERY humid

My house has no water intrusion in the basement. As Worthy points out, there is lots of water used in masonry and concrete. It took my basement over a year to get to the point that the dehumidifiers were not running most of the time. Now they capture less than 5 gallons a week combined for both of them.


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RE: Brand new house...but basement VERY humid

went out and bought a new dehumidifier last night. It holds at least twice as much as our old one and seemed to be doing a much better job. I guess we'll start with that and see how it goes. According to the setting, it was able to get it down to close to 50% humidity (from around 75%). It did fill up overnight so we emptied it this morning. The humidity reading was back up high again though when first turned it back on this AM.

Thanks for the info...


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RE: Brand new house...but basement VERY humid

" As your new slab and walls cure, that water has to go somewhere."

Most of it actually stays in the concrete forever as it cures by hydration.

Any excess will come out.

You can test for condensation by taping some aluminum foil to the concrete with plastic tape (gaffers tape or packing tape work), allowing the foil to stay in place for a day or two, then removing it and seeing if there is a wet spot on the concrete, or on if the surface of the foil that was exposed to the room is wet.

The room side is condensation, the concrete side is water in or moving through the concrete.


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RE: Brand new house...but basement VERY humid

WIth the lack of gutters, your design may rely on a perimeter drain and grading to keep outside water away from the foundation. Combined with proper grading, the lack of gutter MAY not be the source of your problem. Gutters can't hurt, but they might not be your solution.

My last house had a basement with no water problems. Occasionally during a hard rain we would see some water in a corner of the basement. I quickly found the problem was a downspout which came undone and was dumping water directly against the house. The "pool" of water sitting against the house cause some seepage.

WIth properly built new construction, I would think you would need an especially wet season and/or some grading issues to cause major water problems like you describe.

One previous suggestion regarding opening window I do disagree with. I understand the reasoning, but I have had different experience.

I recently had a home built. The foundation was poured in the winter and some snow accumulated on the concrete. The house was built and the snow (small amount) was not removed.

Fast forward to the summer. The house is built, but the interior cutout for the basement stairs isn't done yet (it is a walkout basement, so we still have access via sliding doors).

I started having what I though were water problems. Dampness about 18" from the floor on the foundation and standing water on the floor. I wasn't living there yet and couldn't get to the location regularly. I would get everything "dry" only to find water next time I came there.

I called the people who did the foundation. They confirmed perimeter drain, vapor barrier, waterproofing exterior, etc. were all done. We were scratching our heads as to the cause. My contractor suggested condensation. With the amount of water I was seeing, I was tempted to laugh at him. However, I did try the aluminum foil trick mentioned above. Took an 18" square of aluminum foil (saran wrap works just as well) and duct taped it to the wall in several place.

Oddly enough, I never got to test this trick. The day after I taped the sheets is the day they cut the hole for the basement stairs. Contractors were working on the house all week and the doors/windows were open. (Granted, it was not a humid week and we had a good breeze). After that, I have had NO water problems.

Moral of the story - the house was built so tight, the original water was trapped in the basement. It would continually evaporate and condense. WIth no air flow, it had no where to go. Once we had some air circulation to/from the outside, I was able to get rid of the water. Since I had no real seepage/leakage problem, the water never came back.

One last thing... they make dehumidifiers with a built in pump. I like the "Winex" model. It has a standard reservoir plus it can pump water up to 15ft vertical. Much easier than emptying a bucket every day.


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RE: Brand new house...but basement VERY humid

"they make dehumidifiers with a built in pump"

Or you can just connect any dehumidifier with a drain hose to a condensate pump purchased separately.

The pumps are not very expensive.


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