Repair Wet Crawlspaces The Right Way Part II

A wet crawlspace can be a big worry to homeowners and because of this, there are a lot of ideas and advice out there regarding repairs. Last month we learned about some common causes of moisture in the crawlspace and discussed some of the ways that people try to repair wet crawlspaces. Unfortunately, going about this issue in the wrong way can cause more problems than it cures. This month we will look at a few more examples of bad or outdated advice.

  1. Improper drainage system installations – Many crawlspaces have water standing on the ground floor after heavy rains. There are many reasons why water enters, and several solutions to prevent or remove the standing water. The worst solution is to ignore this recurring problem, or repair the problem with a standalone pit and pump. A sump pump alone cannot pump all the water that pools around the perimeter or in the middle of the crawlspace. A perimeter drain system is necessary to intercept the water before it enters under the footings and into the crawlspace or basement.
  2. Venting the Dryer into the Crawlspace – This is only considered a repair mistake because homeowners quit trying to replace the dryer duct in the crawlspace after it breaks or clogs. This will pump gallons of water into the crawlspace air causing it to move upward into the wood components because warm air rises and the vapor in the air will condensate on the structural components and sub floor causing mold and deterioration.
  3. Insulating Heat Ducts in a Crawlspace with Fiberglass – Ducts in a vented crawlspace will condensate and the fiberglass will soak up all of this excess water causing mold to grow around the duct in the fiberglass.
Repair wet Crawlspaces

Additional Problems

Improper Gutter, Downspout and Perimeter Drain Maintenance – Gutters are designed to take roof water away from your home and foundation. Allowing clogged gutters to over flow water will result in more water entering the crawlspace. The biggest mistake of all is allowing the downspouts to drain the water right up against the foundation. The downspouts should be extended at least 6′ to 10′ away from the home to prevent roof water from entering the crawlspace. Your Perimeter Drains should also be inspected for clogs or damage and undergo routine maintenance/flushing to ensure they are directing the water away from the foundation.

Renovations without Vapor Barriers– There are many older homes that have survived just fine with their current crawlspaces/basements until they are renovated to improve the energy efficiency by air sealing and insulating. Older, less efficient homes allow a lot of the water vapor in the crawlspace/basement air to be moved out of the home through convection from outside air. When the home is sealed and insulated, that water vapor is still rising from the crawlspace/basement but now it has nowhere to go. This is what causes condensation, and eventually mold issues, in the home. To avoid this, it is essential that you ensure your crawlspace is properly vapor sealed, mechanically vented, and insulated before you renovate.  Moisture and humidity issues are not completely eliminated once the crawl space is sealed. In the sealed environment a small amount of moisture or humidity can cause a significant moisture problem unless provisions are made for some level of air exchange with conditioned air. This is accomplished with mechanical ventilation of the crawl space in essentially two ways:

1) An exhaust fan inserted into the crawl space wall removes a small amount of air from the crawl space and it is replaced by drawing a small amount of conditioned air from the living space (through cracks and other openings in the floor above into the crawl space).

2) A small amount of conditioned air (minimum 1 cfm per 50 sq. ft. of crawl space floor area) is blown directly from the heating and air-conditioning system (from equipment located in the living space above and ducted to the crawl space, or directly from HVAC equipment located in the crawl space).

All crawlspaces are different, and should be properly evaluated in order to come up with the specific system that will work for it. If you have concerns about your crawlspace or any other components of your home please call Discovery Inspections to get an in-depth inspection and consultation

For more information on repairing wet crawlspaces go to:

US Environmental Protection Agency

Island Basement Systems

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