Bad Advice: Crawl Space Edition

Not all plastic is created equal

Depending on what blog you’re looking at, you might be told to use vapor barrier. You might be told to use plastic sheeting. You might be told to use plastic. It’s all unspecific (unless the blog is getting a referral bonus for linking you to exact products) and this is where you’re sunk before you’ve even started.

Proper encapsulation requires proper products, and a technique that most DIYers just won’t have. Most plastic sold in home improvement stores isn’t thick enough and isn’t remotely durable. Even the blogs that recommend a thickness recommend something far thinner than you need to be effective - because that’s what’s available in the store.

Installation woes

In order to do its job, a true vapor barrier has to be installed properly. That means using the right tape (that won’t degrade in the presence of water) and properly sealing it not only on the walls, but at the seams. Every day, we’re in crawl spaces where some sort of plastic sheeting has been laid out and maybe taped along the edge, but the tape has long since broken down and now it just looks like an old tarp balled up in the middle of the crawl space. Don’t waste your time with an incomplete installation.

The seal’s the thing

Here’s a direct quote from a blog that will not be linked:

“Stake the plastic down with landscape fabric stakes to keep it in place. Chances are that someone will have to slide around in the crawlspace later to fix a pipe or run a new cable. A few holes won’t make any difference in performance, and they’ll drain puddles if heavy rain or leaky pipe leaves water on the plastic.”

What.

Why would you even bother sealing your crawl space if you’re going to immediately put holes in it? Proper vapor barrier WON’T rip when someone slides around on it, and you don’t need holes to drain water - you need a sump pump.

Encapsulating a crawl space is hard work and requires the proper materials and tools - which are often proprietary. Sure, you can throw down some plastic sheeting, maybe staple or tape it to the wall, and call it good. You can also throw a bedsheet over your pool for the winter. Just because you can do it, doesn’t mean it’s useful, or correct. If you want to put your problematic crawl space out of mind for good, get a professional.