A serviceman installs a vapor barrier on the ceiling in a basement

Whether you’re having your dream home constructed or remodeling your basement, you may be thinking about installing vapor barriers to keep moisture and mold from ruining the structure’s integrity. After all, it’s wise to be proactive about dealing with moisture issues in the crawl spaces.

All property owners agree that humidity and related issues are common in basements. The main reason is that this space is located beneath the ground or grade level, so it gets little to no sunlight or ventilation. 

Besides, sound insulation in the basement is key to achieving optimal heating and cooling performance in your home. So, you might be interested in going a step ahead and installing vapor barriers for an additional layer of protection.   

However, to most homeowners’ surprise, installing vapor barriers in the basement isn’t always a good idea.  

So, should you spend money to get a vapor barrier in your basement? 

Let’s find out! 

When Are Vapor Barriers in Your Basement a Good Idea?

It’s a smart move to install a vapor barrier in your basement if the walls are unfinished and you know which side of the insulation it’s supposed to go on. In this case, the plastic sheets will help prevent moisture damage on the walls.  

But remember that basement vapor barriers can do as much harm as good, depending on where and how you install them. So it would be best to keep your home, the climate, and the basement design in mind. Keep reading to know more.   

When Are Basement Vapor Barriers NOT a Good Idea?

You should avoid installing vapor barriers in your basement if the walls are already finished and you have your kitchen or bathroom down there. You must know that vapor diffusion happens from all sides—from the soil, from the humid indoor air, and from the outside in summer. 

Hence, vapor barriers only trap the moisture between the insulation and drywall since water tends to condense on a polyethylene vapor barrier. 

Eventually, the trapped moisture will result in sill plate damage and create the perfect environment for mold growth (because basements are already prone to this problem). 

It may also lead to wood rot, which will require at least $600 to repair. Not to forget, you’ll have to pay an additional $4,000-$5,000 (or more) for mold remediation in the basement.   

That said, there are instances when you can safely install vapor barriers in a finished basement. It’s when you have proper systems in place for groundwater control, like gutters, drain tile systems, and downspout extensions. You’ll also benefit from having a graded yard with a slope away from the foundation. 

In the best-case scenario, you’d have all or a combination of these to ensure effective waterproofing of your basement before installing a vapor barrier. 

When and How to Install a Vapor Barrier in Your Basement

A hardhat, roll of vapor barrier, and staple gun sitting atop a piece of OSB

The right time to install vapor barriers in your basement is before the construction or remodeling work is finished, meaning when you haven’t put the insulation on the walls. In fact, they may be necessary at that point to fortify the building foundation since the plastic sheets prevent water from damaging the property’s structure. 

In other words, an unfinished basement will benefit from protective barriers. The plastic layers keep mold and mildew from growing, which don’t only compromise the air quality but also show up as water damage along the drywall base. 

Later, when humidity levels increase, you’ll probably start seeing rotting and structural damage. 

Now, the question is: Should you install the vapor barrier before or after the insulation?

The answer is that it depends on your area’s climate and the moisture and humidity levels. 

Warm Climates      

People in warm climates have cooling systems installed in their homes to ensure the indoor air provides a comfortable environment, while the air outside is warmer because of hot weather conditions.  

In this case, you should install vapor barriers outside the insulation. In other words, the insulation should go first, the vapor barrier second, and the drywall last to ensure the home is protected against outside heat. 

Cold Climates      

The basement area in homes located in colder climates remains warmer because of the heating systems installed. In addition, the hot indoor air can produce moisture after coming in contact with cold concrete walls.

For this reason, homeowners must install the vapor barrier on the interior side of the insulation or before the insulation and drywall. 

A vapor barrier installed in a wall before the insulation and drywall is added.

We acknowledge that the climate isn’t always black or white. Still, a good rule of thumb to determine if a vapor barrier should go before or after the insulation is to identify the typical weather conditions in your region. 

For the most part, check where the hot or humid air is coming from. If the answer is indoors, you must install the vapor barrier on the interior side of the insulation. On the contrary, if the hot air comes from outside, the protective layer should go on the exterior. 

Remember that properly installing a vapor barrier in your basement is critical to achieving optimal protection against moisture and related issues on your basement walls.     

Case in Point – Vapor Barriers in Florida and Arizona?

Florida has a warm and humid climate in the summer, so yes, you should consider installing vapor barriers in your basement before it’s finished. However, ensure they face outside your home for the best results. 

It’s a good idea to get the extra layer of moisture protection to keep water damage at bay in Florida, the Gulf Coast, and Hawaii. 

In general, if you live in an area with a mixed climate (summers are hot and humid, and the winters call for heating systems), you can use vapor barriers to ensure your basement doesn’t become the victim of moisture attack. 

On the other hand, people living in a dry, desert-like climate in Arizona don’t necessarily need vapor barriers in their basements. 

Since houses in this state don’t receive much moisture throughout the year, vapor barrier installation can create issues in your basement. The plastic sheets won’t only trap the humidity in your basement but also handle the hot air poorly.   

The bottom line is that installing a vapor barrier in your basement is recommended unless you live in a region with high humidity year-round.

Factors to Consider When Deciding to Invest in a Basement Vapor Barrier

In addition to the climate in your area, you must consider the following factors when determining if basement vapor barriers are suitable for your home or not. They’ll also help you choose an appropriate material for a  basement vapor barrier.  

Cladding Materials

First and foremost, you must check the wall cladding materials used in your basement. Builders mostly use bricks, fiber cement, wood, and stone. Double-checking the materials aims to determine their absorbent properties and whether they’ll release or retain water vapors. 

In the former case, you’ll have to be prepared for moisture problems and require vapor barriers for added protection of the basement walls.    

Construction Materials Used in Your House

Next, you need to check if vapor barriers are compatible with the construction materials used in your home. 

For example, if your builders use steel, you must know that water vapor can damage it over time. In this case, installing vapor barriers will help avoid the problem of corrosion and maintain the structural integrity of your house.   

Basement Insulation

Loose-fill fiberglass insulation is shown in a wall before the drywall is hung

It would be best to also focus on how well your basement is insulated. Insulation plays an integral role in deciding how much water can pass through and remain inside an area, so you must plan accordingly.   

Permeability Levels 

Vapor barriers have different permeability levels, telling you how much water or moisture they allow to pass through the plastic sheet. 

If you live in a warm climate, you must invest in a highly permeable vapor barrier that can effectively prevent moisture build-up. On the other hand, you’ll be okay with one of low permeability in a dry climate. 

Ideally, you should look for a balance to ensure water vapors can pass through easily and won’t be trapped inside your basement walls. 


Proper installation of basement vapor barriers is critical to avoid moisture problems. Make sure you hire the best experts for this job with years of experience and an excellent industry reputation.

They’ll know how to efficiently install the barriers while letting the walls breathe and keeping the moisture from getting trapped inside. Moreover, they’ll use proper techniques to help you avoid mold growth and enjoy living in a fresh, healthy environment in the long run.   

The Best Basement Vapor Barrier Materials

Polyethylene plastic sheets typically work best for basement vapor barriers. Plastic is the most commonly used material for vapor barriers in all spaces. 

Most experts use 6mm sheets to ensure the barrier is thick enough to withstand moisture. Plastic is less permeable than other materials, so you can rest assured that water in moisture or gaseous form won’t pass through the barriers. 

However, if you don’t wish to use plastic for basement vapor barriers for some reason, here are a few alternatives you can consider:

  • Foam board insulation 
  • Aluminum foil
  • Builder’s foil 
  • Exterior sheathings
  • Coal tar pitch or asphalt
  • Paper-backed aluminum 

Plywood may also work as a barrier in some homes, but keep in mind that none of the alternative materials will be as effective as plastic in stopping moisture from seeping through the ground of your basement and preventing mold and mildew growth.

A carpenter installing plywood as insulation to prevent home heat loss

If you go for plywood, try using it with a finishing veneer coat. Again, this won’t make a completely impenetrable barrier, but you won’t have an issue if you live in a region that’s not so moist all year. 

Should You Install a Basement Vapor Barrier or Save The Money? 

No matter your plans for the basement, it can be a great place to store your belongings and save on energy costs. So, it makes sense to protect it by keeping moisture out and avoiding insulation damage.

A vapor barrier is a good idea, especially if your basement is still a work in progress and you live in a mixed climate area. 

This protective layer is installed between the walls and the insulation of your basement to help maximize your home’s energy efficiency, control mold growth, and provide you and your loved ones with a healthy environment. 

Besides, vapor barriers aren’t that expensive. So if installed with all factors and conditions in mind, they can save you a lot of money (and structural damage) in the long run.   

Make sure you reach out to reputable experts before making the final decision. They’ll help you assess your property’s needs, climate requirements, and basement insulation situation, ensuring you make a profitable decision to invest in basement vapor barriers. 

Hiring a team of professionals also means you won’t have to worry about faulty protective barrier installation. You could also discuss the best material for the vapor barrier in your basement before giving the go-ahead on the project. 

This way, you’ll know you’ve made the right decisions to protect your home and your family from the various issues typically associated with moisture build-up in the basement.   

One Comment

  1. I’m so glad I found this! We are building a new home in Florida and we’ve been trying to decide how we can protect the basement from potential water damage. Thank you so much for sharing this!

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