Waterproofing is a critical component of just about any new construction or remodeling project. Though it’s not always the top thing that people think about when setting up design or construction plans. Basic waterproofing measures such as flooring and electrical components are easy to think of, and it makes you feel like you’ve ticked the waterproofing box off the list. So, you can just give in to the more fun temptation of more serious design and construction considerations.

Yet this is just the tip of a much larger waterproofing iceberg. Other water protection measures need to be taken into account. Especially if you want a water incident damaging your investment and you also want to be mindful about preventing mold and mildew in your home.

That’s why most new construction and remodeling projects call for some type of moisture barrier to prevent water from entering critical areas. This includes places like the spaces under your floors and inside your walls, where even a trace amount of moisture can support an unseen mold infestation.

At first, preventing water vapor from humidity might not seem like a major consideration. Yet even small amounts of moisture and condensation from humidity can cause increasingly serious damage to the underlying structure of your home.

In fact, very little moisture is needed to create the perfect breeding ground for mold and mildew. Especially during the summer when the temperatures are warm, mold spores are floating densely in the air, and humidity is at its peak. Of course, once it starts rot and mold can be very challenging to deal with unless you have professional help.

So, the wisest course of action is to be proactive about preventing moisture problems before they let mold, rot, and mildew establish a presence.

How To Tell If I Need a Moisture Barrier?

If you have a new construction home, or you are remodeling a part of your home, you likely need a moisture barrier for your home’s walls or flooring. This is a special type of construction-grade membrane that’s engineered to serve as a barrier to prevent moisture damage to your home’s building materials. Especially when you consider how vulnerable materials like wood and drywall are to mold and water damage.

There is a common misconception that a moisture barrier is only needed in parts of the country with hot, humid climates, or higher than average flooding risk. Though the truth is even homes in cooler climates can benefit from having a moisture barrier installed as part of the initial construction or remodeling process.

It’s also worth noting that the environment you live in will impact both what kind of barrier you need and how to install it. You also need to remember that the moisture barrier needs to go on the inside of the home’s walls or at least outside of the insulation.

Ideally, the placement of a moisture barrier will depend on the climate surrounding your house. It helps to ask yourself “Will heat and humidity come most often from the inside or the outside of the house?”

If you happen to live in a colder climate, then you will most likely be heating your home from the inside which drives the cold out of the structure. This also means that a lot of the humidity will be produced from within, which means that the moisture barrier needs to be installed between the drywall and the actual insulation of the home’s exterior walls.

However, let’s say that you live in a hot, humid climate, where moisture and humidity will frequently surround the structure of your home attempting to permeate the interior. In a scenario like this, it makes more sense to put the moisture barrier between your exterior wall and the insulation to keep it dry.

Do I Need A Moisture Barrier In My Basement

A moisture barrier in your basement or crawlspace is always a wise investment regardless of your environment. You might also want to consider adding one beneath flooring and behind the drywall in high-moisture places such as in your kitchen or any of the home’s bathrooms.

Can A Moisture Barrier Help With Insects?

It’s also worth noting that a moisture barrier can also help protect against a wide range of insects. This includes termites and carpenter ants. That’s because many of these pests are attracted to moisture, and need it to colonize the area.

Once they get established the damage, they can do to the woodwork in your home is massive. These pests can even break down the wood framing of your home to the point that they can cause the entire structure to collapse. A moisture barrier serves as a little bit of a physical blockage against insects, but its greatest value is in preventing the ingress of the moisture they need to infest your home.

What’s The Difference Between A Moisture Barriers & A Vapor Barriers

A lot of new construction and remodeling contractors seem to use the terms “Moisture Barrier” and “Vapor Barrier” interchangeably. While both of them are designed to prevent moisture from permeating your home, they might still be made from various materials.

One of the most apparent differences is that moisture barriers are better at keeping out liquids, and vapor barriers are better at keeping out water in its gaseous state.

A lot of the industry materials used for a moisture barrier can be categorized based on their permeability rating, as well as how they are defined by the International Residential Code.

  • Class 1 moisture barriers effectively cover the vapor barriers with the lowest permeability. This includes things like metal, glass, polyethylene sheets, or other highly effective materials.
  • Class 2 moisture barriers are engineered to cover materials like extruded polystyrene and plywood.
  • Class 3 moisture barriers include materials like gypsum board, concrete blocks, house wrap, and more.


If you have an older home and you are planning a remodel, or you are designing the new construction home of your dreams, a moisture barrier is going to be a sound investment. Not only can it help preserve the integrity of your home, but it will go a long way toward preventing the kind of mold, mildew, and insect infestations that drastically reduce your home’s long-term value.