Friday, May 7, 2010

Top 5 Crawl Space Repair Mistakes

Many homeowners that search the internet for crawlspace repair information end up in home repair forums. While there is some good information out there, there are many examples of bad and outdated advice related to fixing your crawlspace. I have witnessed firsthand the results of bad crawlspace repair and would like to set the record straight on what I consider to be the worst 5 crawlspace repairs I've seen.

1. Adding more foundation vents to the crawlspace - Old buiding codes and bad advice have resulted in homeonwers adding more vents to their crawlspace in order to dry the high moisture content in their crawlspaces. The thinking behind ventilation was that air circulation would force the moisture in the crawl space air to end up outside. Through testing, it has been proven that warm, humid outdoor air brought into the crawl space through foundation vents in the summer can lead to increased moisture levels in the crawlspace. Also, the air movement in a home does not move side to side through the vents, but instead upwards (Stack Effect). This Stack Effect draws air inward from every crawl space vent and up into the living space of the home. A properly encapsulated crawlspace is the only solution to reduce high moisture levels in a crawlspace.

2. Spray Foam a wet or damp crawlspace foundation wall - While spraying open or closed cell foam in your home is one of the most efficient forms of insulation, it is rarely applicable in a crawlspace. Spray foam insulation traps water and moisture in the block wall or between the wall and the foam. This moisture has nowhere to go but UP, especially since a building's air movement is upwards (Stack Effect). Up above the foundation are wood components (sill plate, floor joist, bandboard, and subfloor) that are susceptible to wood rot and mold growth. See my post on spray foam insulation in a crawlspace for more information.

3. Staple a vapor barrier to the floor joists - I have not seen a single crawlspace repair mistake more responsible for wood rot and mold than when plastic is attached to the floor joist system. The thinking behind this is to stop moisture intrusion of the crawlspace air from entering the wood components. There are many problems with this; but the most important to know is that most crawlspaces are vented and the cooler surfaces such as duct work, pipes, and the floor will condensate in the summer. The plastic will trap the condensation up against the floor structure causing mold and wood rot to occur.

4. Insulating a damp crawlspace with fiberglass insulation - This is another example of outdated advice resulting in mold growth. Paper faced insulation is "mold candy". Please read Do not insulate your floors with fiberglass insulation for the complete scoop.

5. 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 stand alone pit and pump (especially a pump in a five gallon bucket). A sump pump alone cannot pump all the water that pools around the perimeter or in the middle of the crawlspace. A perimeter drain is necessary to intercept the water and facilitate it to the pump.

Crawlspace Repair Mistakes that didn't make the Top 5:

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.

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.

Improper Gutter and Downspout Maintenance - Gutters are designed to take roof water away from your home and foundation. Allowing clogged gutters to overpour 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 10' to 15' away from the home to prevent roof water from entering the crawlspace.

Stapling the Vapor Barrier to the Sill Plate

If you live in Indiana, Ohio, Kentucky, or Illinois, and have experienced bad crawlspace repairs, give us a call 1-877-409-2837 or SIGN UP ONLINE for a FREE ESTIMATE.

Thanks for reading the rambling thoughts of a crawlspace inspector,
Larry Ralph Jr.



  1. I mosied on over here after you commented on a posting on my site...

    Excellent information! Not only do you tell us about the problem but you tell us how to "fix" it. Great service to homeowners.

  2. Great tips! If more of the public used the tips you have suggested here, there would be far less of the moisture related problems that we encounter all the time on our home remodeling projects.

  3. Larry, this is an interesting post. We've seen the same issues here in Atlanta, and in the climate here, mold quickly becomes a serious problem. While mold remediation provides us with steady business, it would be better for the homeowner to do a bit of prevention instead. Keeping a dry crawl space is a lot cheaper than paying us to remove mold from your subfloor, floor joists, and crawl space walls.


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