Water in the Crawl Space: Causes and Solutions | HomePro by Frontier Basement Systems

Judy and Layne have over 35 years of combined experience in the home building and remodeling industry, and are now using that knowledge to help answer homeowners' questions with this new HomePro Q&A video series.

In this episode of HomePro, they help a customer who is in the process of selling his/her house. He recently had a home inspection, and the home inspector told them that there is a pond under the house, in the crawl space. He wants to know why that happens and what can be done to fix it.

Layne explains that to build a crawl space type foundation a hole is dug in the ground. "How do you build a pond?" Layne asks. A hole in the ground will always invite water in, unless proper grading and adequate drainage are provided. Water can come from many sources and a combination of factors might be contributing to the accumulation under the house. It can be rainwater diverted to the crawl due to poor yard drainage, improper grading, absent or clogged gutters, or downspouts discharging too close to the foundation. It can also be a plumbing leak pouring water into the crawl space.

When water gets into the crawl, it needs a way out. If you don't provide it through adequate foundation drainage, you will have a pond under the house. You need a good drainage system that will collect the water and divert it away from the crawl and as far away from the house as possible. In houses that sit on flat lots, the best way to achieve this is by installing a crawl space drainage system and tie it to a sump pump. The sump pump will get the water out and away.

Only in a few cases, when the terrain itself slopes away from the house, can the drainage rely on gravity to get rid of the water. In that case, the discharge line to the drain should be extended far out into the yard, and you should be able to see the water coming out.

Water in the crawl space is always bad news. It evaporates into the crawl increasing Relative Humidity levels, which leads to mold, dry rot and eventually, structural damage. The humid and filthy air from the crawl is also carried into the living space, ruining your indoor air quality and many times, triggering mild to severe allergy symptoms in sensitive people.