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Everything beneath your home, explained.

Crawl spaces, basements, foundations, water and moisture: what you’re looking at, what usually causes it and what to do next.

An independent publication. We don’t sell repairs or refer contractors.

Poured concrete foundation walls of a house under construction, with openings for basement windows

What are you seeing?

Start from the sign, not the repair.

The guides

Eight sections, from the soil up to the floor framing. Every guide answers first, then explains what changes the answer.

Tools

Each tool lives inside the guide that explains it, so the number comes with its limits.

  • Dehumidifier size calculator

    Enter the area and how damp it is (or your hygrometer reading). You get the capacity range from ENERGY STAR’s sizing chart, in pints per day.

  • Dew point calculator

    Enter air temperature and humidity, and optionally a wall or pipe temperature. You get the dew point and whether that surface will condense.

  • Can I clean this mold myself?

    Five yes-or-no questions based on EPA guidance. You get one of three answers: do it yourself, call a professional, or fix the moisture first.

Who writes this

Our guides are written by a contractor who works on moisture, water and mold in Virginia. Structural information is reviewed by a civil engineering graduate who evaluates existing homes.

How we research, review and correct our guides

Robert Stulpt

Author

Licensed contractor in Virginia who specializes in moisture, water and mold. Five IICRC certifications.

Daniel Mercer

Structural Contributor

Civil engineering graduate (Virginia Tech, 2008) with more than 17 years evaluating existing homes in Virginia.

Below the Sill is an independent educational website. We don’t provide inspections, engineering or repair services, contractor referrals or estimates. About our experts and contributors.