Fixing a Wet Crawlspace

Upon opening the crawlspace door, the author saw large, obvious patches of white wood rot and black mold.

Before the remediation

The OSB ceiling looks considerably better at the end of the job, after the crew has scrubbed it with a borate solution.

Every surface in the crawlspace was dripping wet, including electrical outlets.

Even the staples holding insulation batts in place were rusty and gleaming with moisture.

Droplets of water were also visible on the filaments of this white fungus.

Moisture condensing on the cold masonry columns on the perimeter of the crawlspace was wicking into the adjacent cripple wall framing and insulation batts.

There was fungus even on the surface of the treated wood wall plate.

In the worst parts of the crawlspace, wood and insulation facings were covered with slick black coatings of wet, slimy mold.

Mold on the face of insulation

The presence of mole crickets also indicated that the space was constantly damp.

The entire crawlspace was equipped with just two small vents. One is shown here as viewed from outside the crawlspace under the exterior deck.

OSB and Tyvek between the crawlspace and the floor protected the floor structure from damage, saving the floor (and perhaps the house) from total ruin. The OSB was heavily attacked by fungus, but could still be cleaned up with brushes and a borate solution.

The author's old battery-powered sprayer is small enough to drag into hard-to-access spaces.

The sprayer allows him to saturate the underfloor OSB with a solution of Tim-bor borate, killing mold, rot organisms, and insects without toxic risk to people.

To finish off the space, the author's crew seals the vent openings with duct tape and mastic.

The crew applies a poly ground cover, sealed to the base of the crawlspace wall.

Carpeting protects the 6-mil poly in the area near the access, creating the perception of a space that should be treated with care.

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