Expert: Stephen Major (Owner--Major Design Group) - 3/31/2007

Question
MR. MAJOR, I DO HOUSE REMODELS, REPAIRS,AND PAINTING. I'M SKILLED IN ALL AREAS OF CONSTRUCTION INCLUDING CONCRETE. I WAS ASKED TO INSPECT AND LEVEL A FLOOR IN A HOME OF A FRIEND. THE HOMES IN THIS AREA WERE BUILT 25-30 YEARS AGO ON AN OLD DRY LAKE BED. I'VE NOTICED MOST ALL HAVE CRACKS IN THEIR CEMENT GARAGE FLOORS. I BELIVE THAT NOT ENOUGH COMPACTION WAS USED WHEN THESE HOMES WERE BUILT. I WENT UNDER THIS HOUSE TO SEE WHY THE FLOOR HAD PUSHED UP ALONG THE MAIN CENTER BEAM. THERE WAS PLASTIC VAPOR BARRIER DOWN ON THE SOIL AND UPON PULLING IT UP I FOUND THE SOIL TO BE WET TO A DEPTH OF MORE THAN A FOOT DEEP. YOU CAN ROLL THE SOIL INTO SOLID MUD LIKE BALL. NO STANDING WATER JUST HARD MUD. MY QUESTION IS HOW DO I GO ABOUT DRYING THE SOIL OUT SO I CAN PROCEED TO LEVEL THIS FLOOR. I HAVE TRIED PUTTING 4 BOX FANS UNDER THE HOUSE BUT LITTLE DRYING HAS TAKEN PLACE. I PULLED BACK THE PLASTIC TO EXPOSE THE SOIL. I FEEL THE SOIL MUST OF SWELLED FROM THE WATER IN IT. THERE ARE NOT RAIN GUTTERS ON THIS HOUSE WHICH I WILL INSTALL WHILE TRYING TO DRY OUT THE SOIL. IT HAS JUST ONE BEAM DOWN THE CENTER OF THE HOUSE AND CEMENT FOUNDATION WALL AROUND THE EDGES. THE BEAM IS SUPPORTED WITH 4X4 POSTS ON CEMENT FOOTINGS.

Answer
Russell,

From your description I assume you are describing a crawl-space foundation.  I'm interested to know where this house is, since location and climate both affect soil conditions.  

The best way to dry the soil is with industrial dehumidifiers. You can normally rent these.  Start with companies that specialize in fire and water damage restoration.  These companies usually have a fleet of dehumidifiers and blowers.  Don't try to dry too quickly or too long, as this can cause excessive joist shrinkage and splitting.  Just get the moisture out of the top foot of soil.  

I can't say if the wetting (and soil swelling) has caused the footings to lift.  Some soils do react this way.

You are smart to try to manage water around the foundation.  Gutters can go a long way here, as long as you can effectively divert the runoff away form the building.  Subsurface drains could help here as well.  The original footing drains may have failed or may be absent.

When you are finished be sure to correctly reinstall the vapor barrier to prevent to possibility of excessive moisture accumulating in the space and causing mold, etc.  I recommend a double layer of 6 mil fire-retardant poly with seams lapped 4' and edges adhered or strapped tightly to foundation walls.

Good luck with this project.

Steve Major