Many homeowners searching 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 While there is some good information out there, there are many examples of bad and outdated advice related to repairing crawlspaces. I have witnessed firsthand the results of unprofessional 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 homeowners 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 - In a dry below-grade crawlspace this method is the most energy efficient.  The problem is that in most below-grade crawlspaces, the foundation or ground floor of the crawlspace are NOT dry.  In fact, a majority of the crawlspaces I run across with spray foam have some form of dry rot in the structural components because the foam has trapped the moisture in the wood.  Sill plate repair is needed if they original plates are untreated. It is not uncommon to see the spray foam become separated from the wall from the moisture intrusion.  Unless the crawlspace has external footing drains, a foundation waterproofing membrane, a foundation sealant, positive grade, and downspout extensions, I cannot ever recommend this method of insulation. 

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.  Floor joist repair is commonly needed after the joists are soaked with moisture.

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". The fiberglass will absorb the moisture from the air, become heavy, and fall to the ground.  Worse yet, if the insulation is stapled, it will hold moisture up against the wood components of the crawlspace.

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. 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.

6. 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.

7. 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.

Additional Problems:

Improper Gutter and Downspout Maintenance - Gutters are designed to take roof water away from your home and foundation. Allowing clogged gutters to over pour 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.

Larry Ralph Jr.

Indiana Crawl Space Repair

Indianapolis Crawl Space Waterproofing

Views: 165851

Tags: crawl, crawlspace, mistakes, repair, space, venting


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Comment by Greg Mitchell on April 30, 2015 at 3:53am

Rotting sill plate and band joist typically is not caused by insulation, but rather inadequate siding, improper flashing, and water intrusion due to high water from floods or snow melt.
Spray foam is not a cause of sill plate rot, but might appear as the cause to those not understanding the likely water source, and repeat exposure to water. Note the fiberglass used in this crawlspace, which again is not the cause of damage to the wood.  The stoop was installed incorrectly and the pavers trapped water against the siding, without being flashed correctly.  Landscapers are often to blame in these instances. This home had a foundation too low for the surrounding landscape, and with a slight pitch toward the house, each large rain or snow melt repeated the slowly progressing damage.  

Comment by Greg Mitchell on April 18, 2015 at 8:48am

Spray Foam should be used in crawlspaces.  

To learn about closed cell foam in crawlspaces please read link below.

Spray Foam Magazine Article discussing seamless crawlspace encapsulation using closed cell foam on walls and sill boxes and sprayed Polyurea liners on the floor.

Comment by Greg Mitchell on April 13, 2015 at 5:48am

Spray Foam Insulation is the most effective, and protective insulation available - especially for a crawlspace.

I do agree that foam cannot be sprayed on a wet surface, which frankly is the same for any insulation option. First and foremost the water or moisture source needs to be eliminated, and any wood replacement that is necessary.  Moisture can be a result of exterior grade problems and water over the foundation, or something to do with the siding or poorly flashed stoop or deck. Another possible source of moisture in sill boxes is condensation, which is a result of high humidity in the crawl and cold wooden sill boxes in winter.  All these issues would need to be addressed before using any insulation. Spray foam is NOT the cause of mold and dry rot.  The water is, and these problems need to be identified and repaired before insulating - what ever choice you make.

Using spray foam the right way does incredible improvements to a crawlspace, and is ultimately going to create warmer floors and lower utility bills.  Closed cell foam is a vapor barrier after 2 inches, so instead of hanging plastic with tape and nails (as I see most crawlspace companies doing) why not use foam.  True crawlspace encapsulation requires insulation be placed on the walls (foundation) and into the sill boxes, which then allows proper mechanical ventilation with HVAC systems, much like a basement.  This is the code requirement for a closed, conditioned crawlspace.  

Again, hanging plastic on the walls has nothing to do with insulating, but everything to do with getting a good before and after photo.  

 Your blog singles out fiberglass and spray foam as being "the worst" repairs for a crawlspace, but you fail to mention your alternative.  I just went through your website, and also did not see what your method of insulating is either.  

I too have seen mold beneath wood in crawlspaces, as well as in other places in a house.  The problem here lies with installation by reckless spray foam companies, not looking at the whole house issues or pre-existing mold and rot.  It has nothing at all to do with choosing spray foam, or fiberglass for that matter.

A good example of proper spray foam insulation installed in crawlspaces can be seen at .

Comment by Kendro Lee on May 26, 2014 at 2:37am

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Comment by jonna lee on April 9, 2014 at 1:24am

Hello guys! I am newly engaged and My fiance and I was wondering what to do. To buy a old house or to build a new house then suddenly I found this blog. Were located in Gold Coast. I will now convince myself to build a new house because of this worst crawl space repairs, this will be my one of the reason why I should invest with a new house. I'm preparing myself for DIY activities and at least I can decide  about ideas in crawl jobs:)

Comment by Bob Daley on January 25, 2013 at 9:56am

Ugh! I read #2 and shuddered--spray foam is great but it should NEVER be used on a damp surface! What a nightmare.

Comment by tedkidd on April 12, 2012 at 7:16am

LOL.  My aunt and uncle have four 50 gallon electric water heater in their summer home, with a recirc, that runs 24/7/365.  I suspect the same goes for the electric floors in the 5 bathrooms.  


I've been down the path of investing time and energy to save other people money they don't care about saving, its not fruitful or rewarding.  Again, "chasing savings here represents negative return on time invested for them" and therefore, for you.  I believe the meat of the energy saving market is people with incomes under $150k, for these people the savings matters more than the time it costs to achieve it. 

Sell them a Navien or leave the heater's alone, adjusting settings only opens the door to complaints.

Comment by Tom DelConte on April 12, 2012 at 6:16am

Hello Ted: just remembered I talked this particular owner into turning their gas water heater down. Even this has backfired on me, 'cause every time I visit I must remember to turn it back up! Have a great weekend, t

ps: my offspring is purchasing a new home from KB Homes, energy star awardee. thank the lord!

Comment by tedkidd on April 5, 2012 at 11:41am

LOL.  Please give me his number!

Seriously, I think people who earn under $150k per year ARE interested because spending $1000 - $3000 too much on energy is a big deal to them.  But they simply don't know the opportunity is that big.  They have no way to measure. (I have a simple calculator, and blogged about this)

With On-Bill financing people can now update and increase the comfort and value of their homes, gain some control over future energy obligations, and not change their cash flow situation by $1.  The energy savings pays for the improvement.  

But I have relatives and friend with nose bleed incomes, and chasing savings here represents negative return on time invested for them.  So if that's your primary client I'd say even calling the utility co attempting to discover total cost probably is time you'll never earn compensation for. 

Comment by Tom DelConte on April 5, 2012 at 11:30am

Ted, yes, it's not my energy bill, the homeowner's not complaining, and they don't care about the cost. This is not a paradigm. This is typical behavior of people in the U.S. It's just not a place where people want to save money on energy costs. It's a status symbol to have high costs to some people! I'm not responsible for this. Remember when John McCain was asked how many houses he owned? Turns out it was 13! All due to the fact that his wife is the daughter of a beer distributor! He's the next customer you want, that's a real opportunity, not me or the people I assist occasionally with light maintenance.

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