Concrete Odor in Basement

[woodburn]

About 16 months ago I had a 16 x 30 addition put onto the house. We put a basement beneath that area. The rest of my existing house has no basement. Anyway, the basement has a very strong, peculiar odor in it. Everything was properly waterproofed, no high water table, no water issues at all! I do run a dehumidifier becuase without it, it will get humid down there, but that's normal. We have no pets and the smell is not musty or mildewy. In fact I cant really describe it, but it's so strong, I can't leave the basement door open, and everything we put down there gets the smell on it. A few people I have had over tell me it's the concrete itself, but it's been well over a year now since it was poured, and to me, it doesn't really smell like freshly poured concrete. Some other info.- It is a very confined space- 16 x 30 and three of the walls are 10 inches thick, and the butress wall (the one next to my existing house) is 12 inches thick. I drylocked the floor just to seal it, and used Zinsser Watertite(masonry waterproofer) on two of the walls. The other two are unsealed on the inside. I have two small windows down there. I keep them closed most of the time, but they have been opened, door left opened, and multiple fans running on high to try to purge the smell. I can't get rid of it! Please help!

 

[hh3f]

This is only my opinion-sounds like the concrete is still curing. That is where the odor is coming from. Because it was poured under a building it will be a longer cure time. If there was a tar sealant put on the exterior and your application of waterproofing on the inside this might take some time because you have locked in the moisture and not allowing for a natural cure. How often do you have to empty your dehumidifier? I would run 2 dehumidifiers if its a lot and wait a year for another application of sealant.. or don't wait at all and put more coats of sealer on. Good luck

 

[woodburn]

Thanks for your input. Because of how thick the walls are, you may be right about the concrete still curing. This is what I have been telling myself all along, but I now that we're going on a year and a half, I am getting worried. I keep the dehumidifier set to 55% humidity level, and I change the bucket once every three or four days. When you say put more coats of sealant, I'm assuming you mean on the two walls that are bare. The two that I've already sealed have two coats already. Another coat on those wouldn't do anything as far as I know. But maybe sealing the other walls will stop the smell of the concret? (if thats what it is)

 

[colebrookman]

Thanks for your input. Because of how thick the walls are, you may be right about the concrete still curing. This is what I have been telling myself all along, but I now that we're going on a year and a half, I am getting worried. I keep the dehumidifier set to 55% humidity level, and I change the bucket once every three or four days. When you say put more coats of sealant, I'm assuming you mean on the two walls that are bare. The two that I've already sealed have two coats already. Another coat on those wouldn't do anything as far as I know. But maybe sealing the other walls will stop the smell of the concret? (if thats what it is)

Yup, that's what I would do but maybe try with more outside ventilation. It's harder now with winter but you can't beat cross ventilation if possible or small fans with open windows. It takes time; it has to dry but you need the air to get out as well. Just one opinion.
Ed

 

[Highbeam]

Concrete smell will last a long time. Inside large dams you can still smell it strongly decades later. As long as the concrete is exposed to that interior space and the interior space is not made stinky by another smell like people and furniture, it will keep smelling like concrete.

 

[d.n.f.]

As opposed to running a dehumidifier (which is a power hog), I am switching to a setup mentioned in last months Fine Homebuilding. The guy ran a six inch duct from about 4" above floor level and exited it out the wall to the outside. Midline the duct was a very low power fan which sucked a lot of air. Screen on the outside to take care of the outside bugs. Said he has done a bunch of installs and it solved the moisture problem. There is some web link to the fan, but I am sure there are others out there.

 

[woodburn]

So it seems most people here feel it's not so uncommon that the concrete is still smelling so much time later, but is the strenght of the smell normal? When I leave that basement door open- you can smell it through the whole house- even upstairs. This is during the nice weather when I had all the windows in the house open, plus FIVE skylites. Also, does anyone else have any thoughts about sealing the other two walls and if that will help?

 

[bostonbaked]

I would as a matter of course seal all the walls and floor with Dry-Lock water proof sealer. Not cheap but effective. It can be purchased in 5 gallon buckets. It will seal out odors and prevent any water infiltration. In my opnion it is a must do first step in a finished basement or any basement where moisture is an issue. Good stuff. Look it up and see what it can do.

 

[backpack09]

Run a fan out your basement window in good weather that will aid in getting rid of that chalky smell.

Personally I love the smell of fresh concrete. I am an engineer and build a lot of concrete seawalls. The smell reminds me of the beach and making money.

 

[woodburn]

I think I might seal the bare walls, but I have also heard that doing that can actually be BAD. Any moisture that is in the concrete, or any dampness that penetrates from outside, normally leaves the concrete by evaporating into the basement. But if the walls are sealed, the moisture will have nowhere to go but up through the top of the concrete, where the sill plate is. This can cause very humid conditions and mold in the upstairs walls. Backpack- you said you are an engineer. What do you think about that? Also, has anyone heared of a waterproofing product called PENETRON? This is what was used to waterproof on the outside, then a layer of tar was put over that before backfilling. Here is a link to the Penetron website. It's actually very interesting- worth a look. Watch the video if you check it out. http://www.penetron.com/en/

 

[bostonbaked]

I'm by no means an expert. That said if they sealed the out side of the foundation that's good. If you seal the inside that's good. The amount of water that has not worked it's way out of the wall I doubt would cause all the stuff your describing. If you look at a can of sealant it does give guidelines as to how long to wait for the (green)concrete to cure before application. It is not a huge amount of time 6 months maybe a year. I have been told by people in the business that concrete cures for decades and develops more strength through it's life time. Some one I'm sure will know if this is true. I'm going by what a form contractor once told me. If the foundation is sealed the only water within the wall is what's left from the pour I would think. I think your making a mountain out of a mole hill for yourself. Relax !

 

[woodburn]

Thanks. You're probably right about the mountain thing! Maybe the problem with inside sealing is more for if you have a problem with leaks from the outside. Then the constant wetness may cause the issue I described. Again, this is just what i've heard. You are definitely right about the concrete gaining strength over time. I think it's something like 40 years! Then it slowly loses strength until it will eventually begin to crumble under the weight of a structure. Also- drylock says the concrete must cure for at least 30 days before application. That's absurd if you ask me!

 

[bostonbaked]

If you have waited all that time don't worry about it. Use the DryLock and you will be happy with the improvement I'm sure.

 

[woodburn]

Thanks. I'll probably be doing that within the next month or so.

 

[Gooserider]

A minor trick I've done that helps with the dehumidifier - I never could remember to empty the bucket, and when I did it was always a bit messy... Our HVAC unit is in the basement and the condensate drains into a little pump with a float switch that probably holds about 1/2 gallon or so between cycles... The hose runs up and out through the sill next to the lines to the outside AC compressor. I decided since the pump was already there, I might as well take advantage of it.

I put the dehumidifier up on a shelf, and found that it had a garden hose thread fitting on the drain outlet (I understand that this is fairly standard). I took a junk washing machine hose, put it on the drain outlet, (removing the bucket) and cut it so the other end just fit into the condensate pump's outlet. Now it's no longer an issue to deal with the bucket, the only difference is that the house now "pee's" a bit more often...

The pumps are standard items and fairly cheap at the local HVAC supply house if you don't have one in a convenient place...

Every couple years I do have to take the pump apart - it starts growing alien life forms, which plug it up and I have to clean them out, no big deal...

Gooserider

 

[woodburn]

Thanks. I'll check it out. Not having to change that bucket would be a plus.