Vapor Barrier Underlayment

Adding a vapor barrier underlayment or drainage mat to crawl space encapsulation, is it worth it? When do you need it and why should you consider installing it? Unconditioned crawl spaces are great places for mold, high humidity, damaged sub-floors, and standing water.

Crawl space vapor barrier underlayment adds another layer of protection. This can make sure the investment in a healthy crawl space will stand the test of time. Unfortunately, this is an area many homeowners skimp on the added protection. Like a battery back-up is to the sump pump, the underlayment is to the crawl space plastic.

image of vapor barrier underlayment_felt

Is Underlayment Worth the Investment

In the grand scheme of things, the underlayment can be about the same price as vapor barrier. Sometimes more depending on the thickness of the product. We offer two types of underlayment. Both are designed to protect the plastic from punctures.

Since the vapor barrier is so important in the overall health of the crawl space, the underlayment is a great layer of protection. When we install the underlayment, we offer a limited lifetime encapsulation warranty. That shows how much we value vapor barrier underlayment.

Read article Crawl Space Encapsulation Vapor Barrier –

Radon and Underlayments

Many crawl space supply houses sell underlayments as ways to improve radon mitigation systems. The EPA does not say an underlayment will improve or hinder a radon mitigation system. They only require the radon system be installed according to their guidelines.

The EPA guidelines for a sub-membrane radon mitigation system are pretty straight forward. Click here to learn more about that. I guess it is possible for the right underlayment to help with radon. I would consider it to be a secondary benefit. The primary is to make the ground plastic last longer.

Underlayments Move More Water

This is another credit given to underlayments in crawl spaces. Is it possible for a flooded crawl space to drain better with underlayments? Yes. After all, it does create a gap between the ground and the vapor barrier. But I would make sure I had a great crawl space waterproofing system installed as well.

Dimple underlayments like the one found on our DIY store can move 18 gallons of water per minute per foot according to the manufacturer and how it is installed. Wow that is a lot of water to move. Upgrading your vapor barrier to include the underlayment is a great value. It can also help keep your crawl space drier than installing a vapor barrier alone.

Dimple Underlayments and Footer Drains

As a side note, dimple underlayments can also be installed on the outside of foundation walls and tied to the footer drains. This will keep your basement or crawl space dry for many years when installed correctly.

I hope you found this information useful. Please comment below if you have any questions or would like to say hello. I am also putting a video for you to watch about plastic underlayments below.

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