house concrete slab moisture

Korey

I live in Southern California. We had an unusually wet winter this year. The house was built in 1963 and has a concrete slab. It is a patio home so other than the front of the house, cement pretty much surrounds it. It has a step down living room which is lower than the rest of the house which is not moist. The concrete slab is moist and has created a mildew smell in the house. There is also a earth smell coming up from my garbage disposal. There is effervescense under the carpet in the upper level room adjoining the lower living room and also in the bedroom. The kitchen floor is tile and moisture can't be detected. I have had commercial dehumidifors and fans going for a month with no results in drying it out. The plummer has found no leaks in the pipes in the house or the sewer line. The insurance company is having a soil engineer come out to see what the water level is in the soil. The soil is sand and clay. The insurance company has said if it is a water table problem it's not covered. My neighbors on both sides have not had any problems. Has anyone had this problem? Is this something that I can fix? Is there something the plummer is missing. There has not been any calcium chloride testing or RH testing.

Bud Cline

Is your subfloor all bubbly and happy or is it producing a white powdery substance?

ef·fer·vesce

   /ˌɛfərˈvɛs/ Show Spelled[ef-er-ves] Show IPA
–verb (used without object), -vesced, -vesc·ing. 1. to give off bubbles of gas, as fermenting liquors.

2. to issue forth in bubbles.

3. to show enthusiasm, excitement, liveliness, etc.: The parents effervesced with pride over their new baby.

ef·flo·res·cence

   /ˌɛfləˈrɛsəns/ Show Spelled[ef-luh-res-uhns] Show IPA
–noun 1. the state or a period of flowering.

2. an example or result of growth and development: These works are the efflorescence of his genius.

3. Chemistry . a. the act or process of efflorescing.

b. the resulting powdery substance or incrustation.

Korey

Hi Bud,
The substance from the moisture is fluffy yellowish white power and seems to grow. It smells like mildew. The plummer said it's not mold or mildew. It is not in my living room which has the largest amount of dirt across the front of the house and during heavy rain get's the most flooded. It definitely is not bubbly and happy.

Bud Cline

That is efflorescence. Efflorescence is basically the rising of natural salts that occur in the cement products. It rises due to the presence of moisture. The moisture is naturally seeking to evaporate so it rises and carries the salts with it along its journey, and once it arrives at the surface it tends to blossom and bloom. If left unrestrained it can almost look like cauliflower in some cases. Anyway that's very basic explanation.

The existence of moisture can be totally natural and normal. You don't necessarily have to have a sub-grade water leak to be experiencing efflorescence but a water leak could also be the driving force causing the efflorescence.

Concrete is also a natural magnet for moisture so to speak. The depth of the water table can have an effect on the moisture in the concrete but so can the environment.

Based on your comments about a "wet winter" and your neighbors not being aware of the same issues, this points to an isolated problem with your property. More than likely your landscaping.

I think your insurance company will back away from this problem shortly and leave you to deal with it. The musty odor is likely from a mild mold/mildew condition. You are doing most everything you can at this point. Dehumidifying is probably going to be your best bet.

Calcium chloride testing will tell you how much moisture is in the slab at the time of testing but that doesn't mean that degree of moisture is there year round. Normally it won't be, it (moisture) can and does change with the seasons. Ca Cl testing may be a waste of money.

The house is fifty years old but how long have you been there. Out of curiosity...where are you in California? East or west of the hills?

Korey

Hi Bud,

Thanks for the 101 on moisture. The water system around the house is a drip system and along with the sprinklers for the front lawn only runs three days a week for 5 minutes a day.

I've been in the house 20 years and haven't experienced this problem before. I live in Orange County, CA. Almost central between LA and San Diego.

I had a water filter leak behind my refrig. and the insurance company sent out a water repair company. When they removed the bottom shelves in my cupboards next to the refrig. they found standing water on the slab. I don't know how long I had the leak. Then they probed the floor in the room behind the refrig. and found it moist, and then the bedroom. There is no dry wall damage because there is a space between the wall and floor.

The insurance company said damage could not be that extensive from a water filter leak.

They sent out a plummer who checked all my house pipes and the sewer line. They didn't find a leak.

I think I'm going to get stuck with the bill.

Thanks for your information. It's helped me understand what's going on.