Damp foundation?


  #1  
Old 08-02-05, 01:03 PM
ahimsa1961
Visiting Guest
Posts: n/a
Damp foundation?

We're converting an unused guest room into a nursery. In the very center of the room, under the old bed, we found that bottoms of the plastic storage bins we had there had a lot of condensation and mold on them, and that they'd obviously been getting that way for several months.

Once we took out the carpet and padding, we patched a couple of very minor cracks in the concrete, thinking that must be where the dampness had come from.

The floor has now been bare concrete for a couple of months while we painted and decided what kind of floor to put down. In the meantime, I've noticed that wherever a can of paint or anything sits for more than a couple of days, the bottom of that item starts to collect condensation. A couple of the paint cans have even developed a little rust.

The floor itself FEELS dry, except for where something solid has been sitting. This happens in the very center of the room. There are no visible cracks, and the floor is more-or-less level. The house was built in 1995.

I know that if we put down wood laminate, we're supposed to put down a moisture barrier, but that's not normal for carpet, and whatever we put down will be ruined if the floor continues to be so damp.

Do you think it's possible that the concrete was just so wet before we patched the little cracks that the water is just still evaporating out, or is there something more going on? How could so much moisture be coming through the foundation?

I'm worried that it's a serious problem, and am not sure where to start for help, but we don't want to waste money on carpet or laminate until this is resolved.

Thanks for any ideas.

Monica
 

Last edited by ahimsa1961; 08-03-05 at 07:10 PM.
  #2  
Old 08-07-05, 12:06 AM
rdn2113's Avatar
Member
Join Date: Oct 2002
Location: Wally World
Posts: 431
Upvotes: 0
Received 0 Upvotes on 0 Posts
Hi Monica,

Before I offer a possible cause, it would be helpful to know more about the room and the condition.

Is the room in a basement? Or is the entire house built on a slab? Is this the only room that has a condensation problem? Does the condensation occur everywhere in this room, or is it limited to a certain area? (You mentioned the center of the room, but are more areas affected?) Is the house built in a flood plain or area where run-off is likely to occur? What do you know about the topography of the property itself - is it infill, lowland, or???? Was there moisture in places where furniture sat, and/or under the carpet pad as well? Do other homes in the neighborhood have the same types of problems?

I know that's alot of questions, but it helps to see the big picture along with the details to help clarify the problem. Also, we need to know both the proximate cause and the origin to determine the problem so we know what to do to fix it.

One way to test the size of the problem in the room would be to snap chalk lines in a grid pattern on the floor, then place containers (paint cans, plastic bowls, etc.), in the squares of the grid. This will give you a good idea of the size and "shape" of the affected area.

OK - now for a suggested cause. Moisture that appears as condensation through a concrete slab is caused by water lying beneath the slab that passes through the concrete. Unless a proper vapor barrier was installed BEFORE the concrete was poured, any moisture under the slab can wick through the concrete. This much you have learned.

Knowing this doesn't help, however. We need to find out where the water is coming from to determine if it can be eliminated or diverted elsewhere. This is why I asked so many questions earlier.

A few thoughts:

> If the house is on a slab, water supply lines are sometimes run under the ground directly under the slab itself. If a small leak occurs, the ground under the slab in certain areas can become very wet over time. If there is no vapor barrier, or it has become compromised, it can cause the effects you describe.
> If the house was built in a "low lying" area, on infill, old stream bed, etc., water can accummulate underneath a concrete floor. Again, without a vapor barrier, the water can wick through.

Run-off can come from multiple sources depending on a number of factors such as those I asked about earlier - even from rain water or irrigation water leaching under the house. These sources can sometimes be diverted, but other times their origin can't be pinned down.

Leaks can be roughly determined by making sure all taps, toilets, etc. are leak free. With all water in the house off, take a reading of the water meter. After about an hour, check it again. If the meter has advanced, there is a leak somewhere. However, it may not be in a location such that it is causing your problem.

It's really important to know where the water is coming from to determine the best course of action. However, assuming it is caused by natural accumulation and not a leak or divertible run-off, then the concrete can be treated and sealed with a product made by UGL called DRY-LOK. It is available at Home Depot. I recommend you treat the floor with this (or something like it) regardless of the type of floor you decide to put down. This is a fairly inexpensive yet effective solution.

Write back and let me know how things are going.

Thanks - and best wishes.

Rick
 
  #3  
Old 08-07-05, 06:50 AM
ahimsa1961
Visiting Guest
Posts: n/a
Rick,

WOW and thanks.

We were away for a couple of days before school starts on Monday, so give me a couple more days to try to answer your questions. I should have mentioned we're in Central Florida, and most neighborhoods around here are built on reclaimed wetlands. (Can you say SWAMP?)

I'll go through all the papers I have an try to answer as many questions as we can. In the meantime, we're going to try the water-leak test today, so I'll have an answer for that, as well.

Thank you again for all the ideas. I'll get back with you when I have some better details for you.

Monica
 
  #4  
Old 08-07-05, 11:52 PM
rdn2113's Avatar
Member
Join Date: Oct 2002
Location: Wally World
Posts: 431
Upvotes: 0
Received 0 Upvotes on 0 Posts
No worries Monica. Life takes time. Let me know what you can when you can and we'll try and figure it out.

Thanks!

Rick
 
  #5  
Old 08-08-05, 01:56 PM
ahimsa1961
Visiting Guest
Posts: n/a
Hi Rick.

We read the water meter yesterday, then left the house for about four hours. Much to our relief, the meter hadn't moved, so I am pleased to say that we can rule out the leak.

The other good news is that we've had a lot of rain the last couple of days, and the floor doesn't seem to be getting damp at all. In fact, the paint cans I've left sitting around the room are all dry.

I wasn't teasing about the location of our house. I don't know (yet) too much of the real history of this area, but I've heard that areas very near us were swampy areas that took a lot of fill dirt to build up enough to put houses on. I wouldn't be at all suprised if that were the case with us.

We don't pay for flood insurance, so I'm reasonably sure that we're not in a flood area, but I'll verify that, as well.

One thing I didn't think to mention before is that this house didn't have any gutters at all when we moved in, and we didn't ever think about the consequenses of that until we found the wet carpet. We had gutters put all around the house about two months ago, so that might be keeping some of the water from standing around the base of the house.

When we do get a good rain (which is often), our grass is spongy, and we can see areas where the yard puddles for a while (maybe 45 minutes) after the rain stops. Greg's dad told us something about French drains (I think), but I don't really understand what that is, or how it would help.

Okay. That's all I've got for now. I'll write more when I can answer the rest of your questions. I had a feeling these things might factor in somehow, though.

Thanks again.
Monica
 
  #6  
Old 08-09-05, 12:28 AM
rdn2113's Avatar
Member
Join Date: Oct 2002
Location: Wally World
Posts: 431
Upvotes: 0
Received 0 Upvotes on 0 Posts
Hi Monica,

Sorry for the late reply, but my computer crashed.

I'm very glad to hear that you don't have a leaky pipe anywhere. That's great news!

French drains may well be needed. You can read all about them here:
http://landscaping.about.com/cs/lazy...nch_drains.htm

It was very wise to install gutters - be sure that any downspouts are constructed in a way that allows the rain water to be carrier as far away from the house as possible.

I'm glad to hear that things appear to have dried out. However, since the condensation has occurred at least once before that we know of, it could happen again. I took to heart what you said about the "swamp". So it sounds like this in infilled wetland. Also, the water accummulation on the lawn is a good indicator of how the land drains. A few thoughts:

> It could be that the builder failed to install a vapor barrier before the slab was poured. I know it's hard to believe a builder might omit a vapor barrier considering the type of ground, but stranger things have happened I'm sure. What this means is that the condensation will likely reoccur.
> Please leave the paint cans in place for a while longer. The movement of water through infill can be very unpredictable. It could take hours or even days for the condensation to reappear after it rains.
> The topography of your neighborhood is important here - runoff from surrounding properties may be a source of the water. Water can move underground a long way, and/or contribute to the underlying level of the water table. In this case, with your property being built on wetland, the water table is likely near the surface, so it wouldn't take much to raise the level enough to cause the moisture problem inside the house. French drains could be very helpful in this case.

Regardless of what you decide to do outside, I would still recommend using the Dry-Lok on the floor. This would provide you full protection should water get past any preventative measures you've taken outside.

Let me know about the other things when you can.

Thanks Monica.

Rick
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: