Two Types of Vapor Barrier Underlayment for Your Crawl Space | Ask A Ninja #55

#AskANinja 055 – Are you concerned about your vapor barrier being damaged by gravel, rocks, or other jagged materials located on the dirt floor of your crawl space? Did a contractor tell you to install gravel to help with crawl space flooding and now your vapor barrier is being damaged?

Great Article – Crawl Space Vapor Barrier Underlayment

Vapor Barrier Underlayment

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9 thoughts on “Two Types of Vapor Barrier Underlayment for Your Crawl Space | Ask A Ninja #55

  1. Work has begun! Vapor barrier out, vents sealed, dehu is drying out the crawlspace since Friday. I am very excited to see it when it's all complete. It's like Christmas in July! I might grab my sleeping bag and camp out down there for a night, lol.

  2. If you are using your crawl space for storage there is no question that drainage matting combined with a 12 mil fiber reinforced liner over the rocky sub-base is the way to go. Every crawl space is different and should be evaluated on a case by case basis when developing a custom protocol for moisture control. Crawl spaces that have a mixed grade and/or sloping lot often have low spots where water accumulates. Perhaps the clay soils are hard and consolidated. A rocky sub-base at a low spot or inside an old pit can be helpful in controlling water intrusion issues. Adding 3-4" of washed stone creates a natural drainage field. The water can then migrate under the rocks and get into the installed drainage tiles and/or laterals protecting the liner above. Deploying extra gravel around a sump pit is also very effective. Keeping the water under the rocky sub-base also helps with the moisture problem. If the crawl space is tight and the customer has a specific budget, drainage matting can also be deployed partially at the crawl space entrance as well as around HVAC equipment to protect the liner from dimpling and tearing in high traffic areas.

  3. Do you have a video showing how to wrap corners a pillars with 10mil vapor barrier? Must be like wrapping Christmas presents, for which I never been good at… Iol at me…

  4. And just a thought to anyone looking for the fabric, I have not looked at what Michael has available, but you can find wide rolls commonly sold as a road base liner so your not working with 4 foot width. Good info Michael.

  5. What's your thoughts on putting down the dimpled underlayment with an 8oz Non-woven cloth on top. Having them go wall to wall and up 6 inches on all walls then have a virgin poly 3 inches down from joists for termite inspection then wall to wall on top of the other two. Have lots of large bolder, rock and unusual bends looking to protect from ripping and potential damage to the encapsulation. I'm looking for a more water wicking cloth material currently just planning on using the same cloth as the french drain fabric.

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