Can I Install New Plastic Over Old in Crawl Space

I received a question about installing new plastic over old plastic in the crawl space.

Installing plastic in the crawl space is both vital, but can also be labor-intensive. Many try to make the process easier by throwing the new vapor barrier over the old vapor barrier to save time and money.

But is this effective? What problems can occur leaving the old vapor barrier in place?

Old Plastic Can Trap Mold

One of the main reasons for removing the old vapor barrier is to clean out mold and any trapped debris that has collected under it.

Old plastics can hide old debris. Old debris can grow mold.

Crawl Spaces are Often a Full of Litter and Trash

Some crawl spaces are used as construction garbage cans. I have seen beer bottles, soda cans, drywall pieces, scrap wood and metal thrown under the crawl space vapor barrier. All of these items could grow mold or damage the plastic.

Odors Get Trapped Under Old Plastic

Imagine you have your carpet replaced, and the cat has been spraying the subfloor prior to laying down the new pad. Most homeowners would do whatever necessary to remove the urine prior to installing the carpet.

Why Does a Crawl Space Smell Like Cat Pee?

Cat pee odors are not uncommon in crawl spaces. Cheap reinforced plastic and debris trapped under old vapor barrier can create odors of all kinds.

These odors can leach into the crawl space. Installing new plastic over old may trap the odors temporarily, but eventually they make their way into the crawl space.

Once odors build in the crawl space, the living space is their next stop.

Installing New Plastic Over Old Doesn’t Really Save Money

I understand the goal of installing new vapor barrier over old plastic is to save money, but at what long term cost?

If you have ever experienced serious odors coming from your crawl space, you realize the cost of doing it correctly is worth it. Once the odors begin to permeate your home, the only solution is to remove and replace new and old plastic. Doing it correctly the first time is what I recommend.

Remove the old plastic, remove all the debris under the plastic, then install the new vapor barrier.

Contact Crawl Space Ninja for Waterproofing and Encapsulation

Please contact us to schedule your assessment to fix your crawl space, basement issue. 


Do you need help with mold removal, crawl space encapsulation, crawl space insulation, vapor barrier, waterproofing, foundation repair, basement waterproofing, or controlling humidity in your crawl space?

If you live in Georgia, Delaware, North Carolina, South Carolina, Tennessee, Ohio, or Kentucky, Crawl Space Ninja can help!


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2 thoughts on “Can I Install New Plastic Over Old in Crawl Space”

  1. Thanks for sharing all this valuable information. I use a dehumidifier and don’t have moisture issues. in my crawl space. However, it really is a crawl space as it’s only 3 feet high and stretches from one end of house to the other. Can I put a three foot wide swath/path of old carpet on top of the vapor barrier to give me something more comfortable to crawl on? The vapor barrier is always dry and dusty.

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