Nasty-Smelling Crawl Spaces: A Case Study

This is the story of three waterproofing contractors’ failed attempts and the final solution to fix the bad moldy smell that had been causing headaches for the wife of a senior couple, long-time residents of a 1950s ranch-style home in the Springton area of Marple Newtown.
The home’s basement heater room was OK, but the bedrooms above the two crawl spaces were damp and nasty-smelling.
The three so-called fixes had been:
1. French drains and sump pumps had been installed in the basement and the two crawl spaces. But the sump pumps never really ran at all, and had little impact on the humid/moldy smells.
2. Three portable dehumidifiers had been installed and set to below 45% relative humidity. They made a lot of noise and heat, and the drip hoses leaked through the crawl spaces.
3. HVAC UV filters and HEPA air filters had been installed. They helped significantly reduce pollen and dust but did nothing to eliminate the musty smell in the bedrooms.
The fourth attempt to fix this problem HAD to be permanent and easy for this senior couple to maintain. This was even more necessary due to recent stay-at-home orders that affect all of us. Indoor air is normally over 300% worse than outdoor air. If COVID-19 is a respiratory illness, then breathing clean “natural” air is now more important than ever.

For homes built since the 1950s, musty or nasty smells in crawl spaces cannot be solved using sump pumps, dehumidifiers, charcoal humidifiers or HEPA UV air filters. The solution for this home’s nasty-smelling crawl spaces was this multi-phased approach:
1. In the two crawl spaces, all dehumidifiers were removed and replaced with box fans and oscillating fans. Vent ports between the basement and the crawl spaces were kept open!
2. To manage exterior surface water along the crawl spaces’ foundation walls, the perimeter that had been covered with flower mulch was replaced with sand and decorative stones/pebbles.
3. Surface water was also managed with drains and spout runoffs at critical points.
The next two proprietary corrections were game-changers and not at all expected by the homeowners. Unlike the basement, which has mold-reducing windows and vents, the crawl spaces have neither, and instead had complete darkness and humidity.
4. Added low-energy light bulbs throughout, and permanently closed open/wet foundation vents.
5. The floors and walls of the crawl spaces became clean and dry after being completely hosed down safely without harmful chlorine bleaches.
The bad foundation smells were due to organic matter (mud) composting in a damp, dark and typically 55-degree crawl space. By adding light and low air-flow fans, removing exterior perimeter surface water, and doing a one-time hose-down cleaning, the bedrooms are now quiet, and gone are the noise, moldy smell and headaches. A permanent no-maintenance solution!