So you’ve bravely decided to tackle installing a vapor barrier yourself. Kudos. You’re either highly motivated, mildly overconfident, or someone who just really likes crawling around under houses. Either way, welcome. Let’s walk you through this process before you end up duct-taping yourself to a joist in frustration.
First Off… What’s a Vapor Barrier Again?
Quick refresher: a vapor barrier is a plastic sheet that keeps moisture from seeping into your home’s foundation, insulation, or framing. It’s the unsung hero that stands between you and mold, rot, gross smells, and the general chaos that moisture brings.
Where Do You Install It?
Depends on where the moisture’s coming from:
- Crawl Space? You’re covering the ground and the walls.
- Basement Walls? On the interior side.
Today we’re focusing on crawl spaces, because they’re the most common—and the most terrifying.
What You’ll Need:
- Heavy-duty plastic sheeting (6 mil minimum, 10–20 mil if you’re serious)
- Utility knife or scissors
- Measuring tape
- Gloves, knee pads, and moral support
- Optional: dehumidifier, crawl space insulation, existential resolve
Step 1: Clean the Space
Yeah, sorry. You can’t just slap plastic on top of junk and call it a day.
- Remove debris, sharp rocks, and anything pointy enough to rip your barrier.
- Remove old vapor barrier (Always!)
Step 2: Measure Twice, Cut Once
Figure out how much plastic sheeting you’ll need. (Spoiler: It’s more than you think.)
- Measure the width and length of the space.
- Add extra for overlaps (at least 12 inches at seams and edges).
- Roll it out!
Step 3: Lay It Down Like You Mean It
Start at the far end and work your way out (trust me—you don’t want to crawl back over your pristine work).
- Lay the plastic smoothly across the ground.
- Overlap seams by 12 inches.
Step 4: Secure the Edges
NOT!
Do not staple your vapor barrier!!! Why would you put holes in the very thing that isn’t supposed to have holes? A stapled or nailed vapor barrier is the biggest red flag rookie mistake we see.
Step 5: Optional (But Smart) Upgrades
If you’re already down there sweating and swearing, might as well do it right. Consider some of the following:
- Add a dehumidifier to control ambient moisture.
- Insulate the walls (especially in colder climates).
- Seal vents to keep humid air from rolling in like it owns the place.
- Install a sump pump to kick standing water to the curb.
- Add proper drainage so water stops showing up uninvited.
Should You Really Be Doing This?
Installing a vapor barrier isn’t rocket science, but it’s also not exactly a Sunday afternoon picnic. If your crawl space is tight, tricky, or you just don’t feel like playing contractor for a weekend, call a pro. We do this all the time. We even kind of enjoy it. (Weird, right?)
But if you’re DIY-ing it—go forth, plastic warrior. Protect your home from the evils of moisture, and maybe brag about it on social media later. You earned it.