Controlling basement moisture


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Old 10-10-13, 11:48 AM
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Controlling basement moisture

I've read quite a few threads and articles on controlling basement moisture. My situation is that I have high humidity in my based (above 65%) even in dry weather. I currently control this with a dehumidifier. I've done tests with clear plastic patches taped to my walls and floor. The walls are concrete block and the floor is poured concrete. I do not get any collection of moisture on either side of the clear plastic. Nor do I have water pooling or collecting anywhere. During really heavy rains, I do get some seepage in 2 spots. But I do not think I have general problems with grading of the soil outside. One spot is the sump exit pipe (which I'll move) and the other is where the water main comes in, so I think the soil is different and I can correct that.

I'm planning on sealing the block with either DryLock or RadonSeal (not sure which yet). I'm also planning on fixing the broken cover on the sump pit. It is currently only partially covered. I will also extend the sump exit pipe away from the house, since this is one of the areas that causes seepage in heavy rain.

One part of my moisture problem, I think, is that I have an open trench 2-3 inches wide around the basement wall. There's nothing I can do about this, and I think moisture comes up through the soi. But covering the sump pit and sealing the walls should help.

The main issue I've been having is that there is no one single major issue to solve. I think it's a combination of smaller things. Living in NJ, I do not think I will ever get to a point where the moisture is below 50% WITHOUT a dehumidifier, but not sure on this. Because I am not getting any moisture on the plastic patches that I tested, I'm under the impression that this isn't a huge issue with the walls as much as it might be the sump pit and trench.

Any advice or additional suggestions to this are greatly appreciated.
 
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Old 10-11-13, 11:22 AM
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Welcome to the forums!

The sump pit/trench are a big cause of moisture, as you said. Are the rim areas insulated with fiberglass (air/moisture permeable) insulation? Is the basement air-sealed (at floor deck) to the exterior/rooms above? Plumbing/wiring holes, etc. allow moisture to the attic with the "stack effect", feeding the attic moisture; http://www.wag-aic.org/1999/WAG_99_baker.pdf

Rim joists move in thickness with the seasonal changes; BSI-023: Wood Is Good . . . But Strange — Building Science Information letting in/out air.


Are you planning on finishing the basement or just reducing moisture? How far away from the concrete wall is the trench?

Gary
 
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Old 10-11-13, 01:24 PM
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If you have any water in the old fashioned, cheap trench leading to a sump, you have a general moisture problem around your foundation. That trench is NOT a waterproofing measure, but just collects water that has already leeked into you home or living space. A sump can easily be sealed.

What ever you put on the walls (inside or outside) will be far more effecting if the moisture outside the space is reduced. Drain tile (interior, exterior or both) will dramatically reduce the moisture level AND the pressure of the walls that causes structural problems (slab and walls) and failures of coatings that always deteriorate.

That little trench with water in it is a sure sign of high moisture levels. The water can come from outside the walls, under the footing under the wall of from under the slab. Drain tile with the bottom below the bottom of the footing will lower the soil moisture level and allow it to temporarily soak up some moisture fron the pesky 2 or 3 rains. - The drain tile works 24/7 to collect water and reduce the pressure that causes many problems.

I had contractor friend that built over 3000 homes on many sites and never wanted a complaint of water penetration, so he autocratically put in both interior and exterior tile (linked) in every home, whether needed or not, as a standard item for every home and would not build a home without it. - It was cheaper than complaints and other material failures.

Dick
 
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Old 10-15-13, 07:56 AM
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ultimately, I'd like to finish the basement. But I'm taking baby steps at the moment. The trough around the outside wall is about 2-3 inches wide, but it's right at the base of the wall. So there's the concrete block wall, a 2-3" trough, and then the concrete slab floor. The rim joist has the fiberglass insulation in place, although I've noticed it's not perfect. There are a few areas, namely where vents or plumbing go out through the rim joist where there are very small gaps so that I can see through to the outside (1/32" or smaller). So I can seal those up pretty easily. There are also 3 windows, if you want to call them that, in the basement to the outside. They are the typical 1'x2' window.

I've never actually seen water in the trough around the walls except maybe once or twice in the past 10 years, and that includes hurricane Sandy. But while there is no standing water in it, I'm sure that it is at least damp with moisture, so that there is moisture evaporating into the basement. I don't actually see any moisture spots on the walls or floor, including the trough. I will be regrading the exterior in the spring just as added insurance against the moisture.

I would love to reseal the exterior wall or put a drain/tile system in place. But, partly because I don't see any standing water, I'm not sure if this will have a big effect. And I don't want to spend that money without knowing it will work.

The frustrating part is that I DON'T see a big pool of water somewhere that I can remedy. So that's why I'm assuming it's evaporative from the sump. To that point, I just sealed it up 2 days ago. So that's one less item to worry about. Next up is sealing the gaps to the outside. But that obviously won't help if I'm getting moisture from the trough.

Would it make sense to put a drain/tile system in place and then fill in the trough?
 
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Old 10-19-13, 09:00 PM
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As Dick said, most of your water will be stopped outside with preventive measures in the future. Back-up systems, interior; 4,5; An Overview of Solutions to Basement Moisture Problems
Air seal the basement, all gaps in rim as little as 1/16" can admit moisture (smaller than air particles), insider storm windows (hair-dryer plastic shrink), is HVAC down there, with an outside air supply, etc.?

Gary
 
 

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