Building Code Says 6 Mil Is Fine. That Doesn't Mean It's Good

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So let's start with something that most contractors use as their excuse for installing six mil plastic, building code.
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According to the International Residential Building Code, the minimum requirement for a vapor barrier in a vented crawl space is six mil polyethylene plastic.
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That's it.
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6 mil.
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Now here's what contractors want to.
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Minimum means minimum.
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It's the absolute bare minimum that you can get away with and still meet code.
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It doesn't mean it's good.
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It doesn't mean it's going to last.
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It doesn't mean it's in your best interest as a homeowner.
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Think about it this way.
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Building code also says you can build a house with 2x4 studs.
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But most builders who believe in quality use 2x6s because it provides space for better insulation, for improved comfort, and soundproofing.
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It's stronger, and according to the internet, R21 insulation in a 2x6 versus R13 insulation in a 2x4 may reduce utility bills by up to 57%.
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It's just a better house.
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Same thing with vapor barriers.
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The building code for vapor barriers was written decades ago, and it hasn't kept up with what we know about moisture control, building science, and long-term durability.
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The code is really designed to keep you from building something dangerous.
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It's not designed to give you the best possible solution.
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And I can tell you from 20 years of experience in thousands of crawl spaces across seven states, six mil plastic is not a long-term solution.
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It's barely a short-term solution.
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Now let's talk about the number one problem with six mil plastic.
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It's too thin.
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Six mil means six thousandths of an inch.
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To put that in perspective, that's about the thickness of a cheap trash bag.
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Actually, it's thinner than most contractor grade trash bags.
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You can easily tear it with your bare hands.
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No tools, no sharped objects, just your hands.
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Now, do you really want something this fragile as the only barrier between your home and ground moisture?
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Here's what happens in the real world.
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Your crawl space isn't some sealed off area that nobody ever goes into, although you may not personally go in there.
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You've got the HVAC contractors going down there to service your heating and cooling system.
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You've got plumbers going down there to fix leaks.
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You've got electricians running wires.
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You've got pest control technicians.
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You've got home inspectors during real estate transactions.
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Every single time someone or something crawl across that six mil plastic, they're creating stress points.
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They're creating tears.
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They're creating punctures.
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And once you get a little tear, it just keeps getting bigger and bigger.
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I've seen six mil vapor barriers that look perfect when they were installed, and six months later, they've got tears.
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One year later, they look like Swiss cheese, and two years later, they're completely destroyed.
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And this isn't an isolated problem.
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This is the norm.
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This is what happens with six mil plastic and moderate to high traffic crawl spaces, which by the way is pretty much every crawl space.
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In fact, I'd estimate that 70 to 80% of the 6mm vapor barriers I inspect are damaged within the first two years.
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That's not a long term solution.
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That's a temporary band aid that's costing you money.
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And I'm Michael Church with Crawl Space Ninja, and I hope you make it a happy and blessed day, and we'll see you later.