Skip to Main Content

Can You Put a New Vapor Barrier Over an Old One?

bad vapor barrier

If you’re contemplating replacing your current vapor barrier, you might wonder, “can I just put a new vapor barrier over the old one?” That is, you’re wondering if you need to take the old one out first before installing the new one.

To answer this question, it’s important to understand how a vapor barrier protects your crawl space, an area highly susceptible to moisture, humidity, and water damage.

In this article, you’ll learn what to do with an old, damaged vapor barrier before installing a new one.

Why It’s Necessary to Keep Your Vapor Barrier in Good Condition

technician installing new vapor barrier

Broadly speaking, a vapor barrier is not a necessity. Neither is waterproofing your crawl space. However, choosing to encapsulate your crawl space and installing a vapor barrier is a wise decision that has many different benefits. A good vapor barrier offers benefits like:

  • Vapor barriers prevent moisture from entering your crawl space, reduce indoor humidity, and make your home more comfortable.
  • Encapsulation minimizes the risk of flooding and standing water in properties.
  • Lower humidity reduces the risk of mold and fungi, protecting the structure of property and health of inhabitants.
  • Reduced humidity improves energy efficiency by making HVAC systems more effective, leading to cost savings and less property wear.

The effectiveness of these measures depends on the overall quality of the vapor barrier and other encapsulation solutions.

Problem Signs of a Bad or Damaged Vapor Barrier

A damaged vapor barrier means moisture problems. Diagnosing a bad barrier can be challenging unless visible damage exists, hence the need for swift action upon noticing issues like these

  • Visible damage such as tears, punctures, and gaps in your vapor barrier need professional attention.
  • Condensation indicates high humidity and potential damage.
  • Standing water suggests structural or plumbing system damage.
  • Wood rot on your floor joists can make them soft, spongy, or brittle, causing the floor above them to sag and become uneven.
  • Mold, often recognizable by a musty smell or surface discoloration, is a serious issue.
  • Cosmetic damage like staining, wallpaper bubbling, and wood warping are signs of humidity damage.
  • Increased energy bills may indicate a humidity problem, as humid air is harder for HVAC systems to process.
  • Increased allergy symptoms in your home.
damaged vapor barrier

If you see any of these problems, call a professional immediately.

Can I Just Put a New Vapor Barrier Over the Old One?

old vapor barrier in crawl space

Sadly, you can’t just cover your old vapor barrier up with a new one. Here’s why:

  • Retaining the old barrier could potentially conceal underlying problems such as mold development or decay.
  • Layering barriers might result in moisture being trapped in between, which could exacerbate the issue.
  • Existing damage on the old barrier could potentially cause damage to the new one.
  • There might be compatibility issues between the old barrier and the new materials.
  • Achieving a precise fit and effective seal is generally easier with a single layer.

So, before you put in a new vapor barrier, be sure to remove the old one. That’s how you get started in properly managing crawl space moisture.

Need a New Vapor Barrier Installed? Cal Foundation Repair of Western Colorado

Noticed signs of crawl space damage or dampness? Don’t want the hassle of tearing out your old vapor barrier? Choose Foundation Repair of Western Colorado today! Since 2005, our team has been restoring damaged crawl spaces. It begins with a free inspection appointment.

Once you’ve booked your appointment, we’ll help set a suitable date and time, explain the process, and provide a written estimate for suggested repairs. You’re under no obligation to proceed with us. Feel free to ask any questions about the proposed work. We’re always here to assist. 

Bad Vapor Barrier


If you do not already have waterproofing measures in place you should think seriously about encapsulating your crawl space. This is a process that has many benefits and very few, if any, drawbacks. Of course, there are some things that you should consider. 

Before Waterproofing 

Before you waterproof and encapsulate your crawl space, you need to be fully aware of its current condition. This means considering whether you have dated or damaged waterproofing measures in place to clear or work around and whether there is underlying damage in your home. Waterproofing when there is underlying damage will lead to the issues being allowed to grow unchecked and unseen. 

Secondly, consult a professional and do some research as to what the best waterproofing products might be for your property. Getting the right waterproofing measures for your home is key to getting the best possible results. If you act too quickly or do not deal with underlying issues, your waterproofing may go wrong. 

The Benefits 

Once you have dealt with any underlying issues and you have found the right waterproofing products for your home, the process of installation is quite simple. The benefits of waterproofing your crawl space are many and varied, too. Primarily, a waterproof crawl space is a safer and healthier crawl space that will protect the environment within your home. After all, your crawl space is a part of your property even if you don’t see it often. 

Another benefit to waterproofing is a general stabilization in the wider climate of your home. Properties with fully encapsulated crawl spaces tend to have better heat and cold retention, higher levels of energy efficiency, lower energy bills, and fewer fluctuations in the interior temperature and humidity rate. This makes the home a healthier and more comfortable environment to be in. And, while there are more tangible benefits, we feel that the biggest benefit is this level of comfort and safety.

While it’s easy to categorize a ‘bad’ vapor barrier, it’s harder to identify a good one quickly if you lack experience and training. However, knowing the difference between a good and bad vapor barrier is key to your home’s health, so it is best to contact a professional. 

‘Bad’ Barriers 

Arguably, there are only two ways in which a vapor barrier can be ‘bad’. Firstly, it can be damaged in some way, whether through accidental incidents or through inherent defects. Secondly, it can be unfit for its intended purposes. Under these circumstances, a vapor barrier can be classed as ‘bad’ for your property. However, there are many more cases in which a vapor barrier can be non-ideal. 

Vapor barriers can be categorized by their width and grade. Barriers as thin as 6mm can be found, for example, but we would recommend that you never stray below 8mm in thickness. Thinner barriers are more prone to tearing and puncturing when put under pressure. Vapor barriers can be found in 3 grades, too, and while they each have their benefits, we would never recommend a grade 3 as these are porous and will let water through. 

‘Good’ Barriers 

Getting a ‘good’ vapor barrier means getting a barrier that is tough enough to stand up to the job that you have in mind for it. This means protecting your home passively, but also standing up to pressure and use when needed. This is why you should have thicker barriers, where possible, and if you intend to use your crawl space for storage, we recommend a 20mm reinforced barrier for optimal tear and puncture resistance. 

As for grading, we would always recommend a grade 1 barrier for use in a Colorado crawl space. While grade 2 vapor barriers do an excellent job, they are semi-permeable and will not stand up to perimeter saturation. Grade 1 barriers, by contrast, are entirely waterproof and will not let moisture pass, whether in liquid or vapor form. This makes them the most reliable vapor barriers by far!

Yes! It is possible to simply change out a damaged crawl space vapor barrier rather than replace the whole waterproofing system. However, in some cases, this may not be possible. It all depends on the nature of the damage. We don’t recommend tackling this on your own. Contact Foundation Repair of Western Colorado for a free crawl space inspection to determine the best fit for your home.

Michael Wilcher

Michael Wilcher

Michael Wilcher is the Content Lead at Groundworks, helping us to answer all of our customers biggest questions about foundation repair, basement waterproofing, crawl space encapsulation, and concrete lifting. In his free time, Michael enjoys collecting vinyl records, watching Formula 1 Racing, and reading philosophy. He holds an MPhil from the University of Cambridge.

Publish Date:

Last Modified Date:

Foundation Repair of Western Colorado Service Map

Our Locations

Grand Junction

2575 U.S. 6 & 50, Unit A
Grand Junction, CO 81501