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12 mil vs 20 mil crawl space vapor barrier, which will I need?

You may find it tough to decide between the 12 mil and 20 mil crawl space vapor barrier. Now, every homeowner doesn’t understand vapor barrier thickness and that’s fine. Think of it like a blanket and cover. As fall approaches, a thin sheet is enough to keep you warm. When the deep winter sets in, you need something thicker to protect you. This is when a big thick cover works just fine. You see, the 12 mil crawl space liner can protect a crawl space but the 20 mil vapor barrier can protect it better as it’s thicker. If you still don’t understand, keep reading.

So, do I need a 12 mil or 20 mil vapor barrier?

To answer that, we need to know what your crawl space looks like. For most American crawl spaces, the 12 mil crawl space vapor barrier is used to cover the crawl space walls. Most crawl space walls are very similar and the 12 mil does great protecting them. It’s a completely different story when we discuss the crawl space floor.

Which Crawl Space Vapor Barrier Is Appropriate?

If you have a hard rocky crawl space floor, a thicker crawl space liner is the best option to go with. You don’t want to risk having to encapsulate your crawl space again, right? Also, if you’ll be storing items on the vapor barrier and walking on it, the 20 mil crawl space vapor barrier is going to be the best fit for this scenario.

If you have a crawl space floor that is smooth and soft, the 12 mil can be enough. If you won’t be storing items on the liner or walking on it much, a 12 mil size would be appropriate.

The question to ask, “what does my crawl space floor look like?”

Personally, I recommend going with the thickest crawl space vapor barrier, which would be the 20 mil. If I’m going to invest in crawl space encapsulation, I want to make sure I never have to worry about the crawl space again. Between radon gas and smells, the 20 mil would certainly be the safest route to take. The right crawl space vapor barriers will block both smells and radon gas.

Crawl Space Materials You Need To Be Aware Of

The materials that make up a crawl space vapor barrier are very important. As a homeowner or DIYer, you should at least be aware of them. If you’ve never bought vapor barriers before, make sure you pay attention to what I’m explaining here.

You can’t expect a regular vapor barrier to do the job of a crawl space vapor barrier. There’s no comparison, it’s like apples and oranges. You need to make sure you’re using crawl space vapor barriers, no other vapor barrier compares. Plastic sheeting is often made from recycled materials that are low grade.

With that said, you want to make sure your 12 mil, 20 mil and all crawl space vapor barriers you buy are made from virgin polyethylene, aka “high-grade materials.” High quality crawl space liners can last for decades. The other cheaper versions won’t last long nor will do the job you need them to do in your crawl space.