Most people would say that any amount of water in the crawl space is too much.
The reality is, that most have some amount of water—-even if it is condensation trapped under the ground cover—-where any effect it could have on the house structure is minimized. Many crawl spaces show signs of past moisture—-with high water marks on the foundation and other structures, while others have actual standing water in them—-sometimes even on top of the plastic ground cover.
It is very important to the health of the home to control moisture levels. The high water line in the crawl space pictured below is pretty obvious—-and may actually date to the time of construction. The hole in the foundation at the center of the picture is a “gravity” drain that was installed to drain the crawl space during construction—-before the roof is installed. These gravity drains prevent the “swimming-pool effect.” These drains can just as easily flood crawl spaces from the outside if exterior water sources aren’t controlled properly. They can also act as an emergency outlet in the event of burst plumbing pipes.
In this next picture the high water mark visible on the chimney (and on the support post to the left) happened since original construction. The water would have been at least 5 feet deep—–most likely accounting for the new water heater visible in the background.
Take a look at this next picture. The grey “socks” on all of these support posts are stains from long standing, but seasonal, flooding—-perhaps every winter this crawl space becomes a swimming pool.
When conditions in the crawl space get this bad, in this neck of the woods, it can be a big problem. Water evaporates and becomes—-“water vapor” (a gas). As the water vapor rises through the home, it condenses back into water on the first surface it reaches that is cold enough. This might be windows in the living space or the roof sheathing in the attic. When this happens in the attic, the roof structures can be destroyed just as badly as the structures in the crawl space itself. In this next picture you can see how all of the roof sheathing is black with fungal-growth—–mold—-even right next to the vent. Even in well vented crawl spaces and well vented attics, this much water in the crawl space is going to be a problem for the house.
Too much water in the crawl space is never enough—-it is too much.
Charles Buell, Seattle Home Inspector
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