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Cinder block basement damp - advice appreciated!

Posted by Nic77 (My Page) on
Fri, Mar 15, 13 at 22:58

Hi, this is my first post. I have been researching ways to dry my basement, and luckily came upon this site. I've read lots of your advice to other home owners and I'm hoping to get some opinions here from experienced folks like yourselves.

About this house: Built in the late 60s, one story ranch about 900 square feet. Basement is unsealed cinder block foundation, and the basement was partially finished when I bought it 5 years ago. Just adjacent to the front of the house is a porous rock hill.

About the problem: The house has always been damp. I run a 60 gallon dehumidifier year round. In the summer I have to empty it twice a day, in the winter, every few days. Mold is growing behind the plastic/sheetrock in the finished parts of the basement. It has even grown in small patches upstairs. Mildew grows on my shoes in the closets upstairs, and my clothes have a musty odor. In the unfinished sections of the basement where the cinder block is exposed, I can see that it was not sealed and there is a lot of efflorescence with lines up to about 3 feet. In three areas when there is a lot of rain or the ground becomes really saturated I get some water on the floor. Not a significant amount, I'd call it a small puddle.

What I have done so far: I had three different "basement specialists" look at the problem. Two recommended interior french drains and the third recommended trying a sump pump only in an effort to save money. One used some type of dampness measuring tool on the exposed areas of cinder block where the water gets up to 3 feet and he said it was very high. I can't remember the exact number. I replaced all the windows in the house this fall - the old ones were wood, riddled with mold and so drafty that they were constantly wet throughout the winter with the temperature difference. I have also fixed my drain spouts to run away and down the hill from my house.

What I plan to do: Replace basement door - it's just plywood and let's a lot of cold and wet in. Fix the grading this spring. But, what I really need to focus on is the water in the cinder blocks, the mold and improving the air quality in my home.

Questions: Based on the amount of water stored in the walls, is the only way I can get my basement dry and improve the air quality in my home by installing interior french drains with a pump and back up power source?

Would an exterior french drain along the south facing side of the house/hill help? Is there anything else I should do or consider doing outside?

Is sealing the cinder block an option or is it too damp for that to work?

Thank you for reading!

Follow-Up Postings:

RE: Cinder block basement damp - advice appreciated!

It would help to know your climate zone, though I figure it's mixed humid or otherwise you wouldn't be running run a dehumidifier year round. (60 pints, not 60 gallons?)

Your basement water leakage problem is exacerbated by the poly vapour barriers in the walls. Unfortunately, the only answer is to remove all the finished walls back to the block. You may have the same problem abovegrade too.

North American Hygrothermal Zones Building Science Corp.

RE: Cinder block basement damp - advice appreciated!

Oh, yes, that would help! I'm in Northwest NJ - close to PA and NY state border. Based on that chart, it looks like I am in "Cold" zone but it gets pretty humid. The part of town I live in (I've lived here my whole life in another part, and the basement was bone dry) is very damp. I'm on top of a hill with the one hill behind me, but my neighbors with land below mine their yards often turn to standing bodies of water / swamps when it rains enough.

Yes, you are right - 65 pint. Gallons would be a real problem, I suppose!

I also left out that I do plan to remove all the sheet rock and plastic in the basement as well because of the mold anyway, but good to know that that might be what's causing the pooling of water.

I found this site in another post on here and think maybe I need to seriously consider the grading outside and creating swales to redirect the flow from the hill? It seems like a really big job!

RE: Cinder block basement damp - advice appreciated!

First, try to ascertain where the water table is. Just because you're on a hill doesn't mean the water table isn't high. If the water table rises above your footings at any point, an interior system might be indicated. That's because water could be coming up through the slab or at the joint where the wall meets the poured footing.

If the water table isn't that high, the only sure cure would involve excavating all around and using one or more of a number of different waterproofing products. These include spray-on membranes, bentonite, plastic bubble membranes, peel and stick and crystalline products.

If there's a surface water problem, yes, swales might be helpful.

But before that, look closer to home. Are your eavestroughs clean and functioning? Where do the downspouts exit? They should be sending water at least 10 feet away from the foundation. Is there a good slope down from the foundation to surrounding soil. I've seen many homes that sit in a depression--either because the original builder put the first floor too close to grade, or subsequent owners altered the grading. Not to mention the gardening types who load up on thirsty plants next to the foundation and water away like crazy.

Next time it rains, go outside and check what's happening.


Mildew grows on my shoes in the closets upstairs, and my clothes have a musty odor.

This is a separate problem and very likely the result of inadequate insulation on the closet walls. So moisture condenses inside--or even on--the interior walls during the winter. You can usually solve this problem by keeping the closet doors open during winter or providing an additional continuous source of heat. It's a reason to avoid placing closets on outside walls of a home, and especially corners where three and four stud framing cuts the R levels drastically.

This post was edited by worthy on Sun, Mar 17, 13 at 16:49

RE: Cinder block basement damp - advice appreciated!

Thanks worthy! Do you have any recommendations on how to find out about the water table? A basic internet search is not really turning up anything useful.

Eavestroughs and downspouts are clean and functioning, and take the water at least 10 feet away from the house, down a hill so I'm sure the path of that water is moving away from the house. Something that just occurred to me as odd now that I'm thinking of it is that this house only has 2 downspouts, on the side of the house where the land goes downhill. Maybe that was the previous owner/builders preference because of the natural landscape with the hill, but now that I think about it, the exposed wall that has all that efflorescence up to 3 feet is on the side of the house without a downspout... I just always figured the 2 downspouts were doing enough because surely the previous owner/builder would know better, hmm. Do you think that putting in two more on the other side of the house could help?

I definitely need to fix the grading this spring. Here's another thought - on the two sides of the house without the downspouts there are also slate walkways right up against the foundation. Would you recommend removing them and choosing a proper grade instead of the stone?

Thanks again!

RE: Cinder block basement damp - advice appreciated!

This site links to real time observation of water table levels in wells throughout the state of New Jersey. The northwest observation currently shows a water table depth of 16 feet below grade. However, any particular location may have a higher water table due to local conditions.

Since you don't mention bulk water leakage into your basement--though it has filled the blocks three feet high--your problem is more likely poor drainage combined with a complete lack of waterproofing.

The two downspouts on the downhill side of your home may be inadequate to handle the flow. When it's raining heavily go out and check what's happening.

Walkways up against the foundation can cause problems if they are not sloped away from the home. Poured concrete is a big culprit as the ground next to the house has been excavated and unless it's compacted all the way up to grade will inevitably settle towards the house.

I'm living for the moment in a home built in 1964 where the front porch slab of about 20' square was done just that way. The section adjacent to the front wall has dropped about four inches.

This post was edited by worthy on Mon, Mar 18, 13 at 1:21

RE: Cinder block basement damp - advice appreciated!

" They should be sending water at least 10 feet away from the foundation."

what is their altitude relative to the basement floor?

The distance is not as important as the height relative to the floor.

When houses with basements are built, they are constructed in a hole (or maybe a cut into a hill).

If you discharge gutters into the hole (now back-filled) and the soil around the old hole does not allow the water to escape, it runs right back to the foundation.

RE: Cinder block basement damp - advice appreciated!

Pictures would help!

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