Foundation Stabilization and Moisture Control in Manquin, VA

Challenge

This Manquin, VA homeowner contacted us with concerns about their foundation and crawl space. They had noticed a bowing wall inside the home and wanted to know what could be done to address it.

At the inspection, our team found that the girder stopped about 20 feet short of the foundation wall, meaning part of the home did not have any support in this space.

We also found that high humidity and excess moisture had created several issues in the crawl space. Water vapor rises from the ground, which is exposed due to the existing vapor barrier being torn and displaced. Open crawl space vents also allow hot humid air to flow into the crawl space raising the relative humidity and resulting in mold and mildew growth.

Moisture is absorbed by the fiberglass insulation in the joists, and by the wood substructure. Moisture damages the fibers of the insulation causing them to separate and fall. As the wood absorbs moisture, it can begin to rot or soften, wood rot usually begins to occur at about 19% wood moisture content further compromising the structural stability of the home.

Solution

To address the bowing walls, we need to stabilize the foundation. To achieve this, we first added supplemental beams to span the 20-foot gap to the foundation wall. We also installed foundation support jacks to support the beams. To install the jacks, we first dig and pour a footer for the jack to sit on. The jacks are adjusted to stabilize the foundation and can be adjusted if there is any future settlement.

Now that the foundation is stabilized, we can address the moisture problems that can compromise the home’s foundation. To protect the crawl space from moisture, we need to control the relative humidity in the space. After the crawl space was cleaned of all debris, the old vapor barrier, and fiberglass insulation, our team treated the wood substructure with an antimicrobial to kill the mold.

To stop moisture from flooding into the crawl space, we began by sealing the crawl space from the earth’s moisture. This is achieved by laying down a heavy-duty vapor barrier that can withstand service persons working in the space without being damaged. The liner is sealed at all seams, attached, and sealed to the foundation walls 6-8 inches above outside grade, and all piers are wrapped and sealed. The next step in sealing the crawl space from outside air is to block all vents, seal the rim & band, sill plate, and any penetrations through the foundation wall to outside.

Then we insulate the foundation walls with closed-cell spray foam insulation. Insulating from the foundation walls extends the thermal boundary of the home to the floor of the crawl space and reduces heat transfer through foundation walls. A 2-inch viewing strip is left at the top of the foundation wall for termite inspections.

The final step is to install a dehumidifier. Though we have prevented as much humid air as possible from entering the space, air and moisture can find its way through exceedingly small spaces, so we need to control the humidity under the home. The SaniDry Sedona dehumidifier does this by cutting on when the relative humidity increases over 55%, keeping the humidity below 60%, the point at which microbial growth can occur. This unit pulls excess moisture from the air, filters the air, and circulates dry air throughout the crawl space.

This solution has allowed the homeowners to stabilize their foundation and protect it from future moisture damage and rot.