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Crawl Space Moisture Barrier

Installing a crawl space vapor barrier is one of the most cost-effective ways to improve your home and prevent the need for future repairs.

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In the grand scheme of things, one of the most important ways you can mitigate crawl space moisture is with a crawl space moisture barrier. Crawl space moisture is a problem that many homeowners deal with, but it’s not a problem you need to deal with over a long period. Alongside other methods of managing your crawl space, you must have a crawl space moisture barrier to decrease water vapor entry. Here’s what you need to know about the process of installing a crawl space moisture barrier in your home.

What Might Indicate That You Need a Crawl Space Moisture Barrier? 

First, you might want to know a little bit more about the warning signs that a crawl space moisture barrier is necessary for your home. If you’re seeing any of these concerns, you may need to install a crawl space moisture barrier in your home. 

  • High Indoor Humidity 

One of the biggest problems your crawl space may face if you don’t have a crawl space moisture barrier is a problem with high indoor humidity. High humidity levels can go through your crawl space and into the rest of your home extremely quickly, which means a high level of humidity in the crawl space will turn into a high level of humidity in the rest of your home. 

High indoor humidity is a gigantic concern. Not only does it impact the crawl space, but it also impacts the rest of your home as well. This humidity problem may end up impacting all elements of your home, ranging from condensation on surfaces throughout your home to sticking doors and windows in various places in your home. 

  • Dirt Crawl Space Floor 

If your crawl space has a dirt floor, there’s no way around it: You need to add a crawl space moisture barrier. Dirt floors are particularly bad for your crawl space because there’s no way to remove all entry of moisture from a dirt floor. Even if you dry out the top area of the crawl space, you’re still going to have crawl space moisture rising from it. 

Additionally, it’s very common for dirt crawl space floors to have issues with standing water. This is because of hydrostatic pressure, which can cause water to come up from the crawl space floor due to the sheer pressure of the water. When you have a crawl space moisture barrier, you can keep that standing water from causing crawl space problems. 

  • Mold and Mildew Problems 

Mold and mildew problems are unfortunately common whenever you have high levels of crawl space humidity. For the most part, mold and mildew are so easy to spread that as long as you have a high enough level of humidity, you’re going to end up with mold and mildew that doesn’t just grow in the crawl space but thrives. 

For the most part, you need around 70% humidity to cause mold and mildew to thrive in your crawl space. If you have around 70% or higher humidity in the crawl space, you’re almost certainly going to end up with mold and mildew. However, mold and mildew can also be a problem if you have lower than 70% humidity because it’s all about the unique positions your crawl space is in. Either way, a crawl space moisture barrier is a helpful way to avoid mold and mildew.

How Can a Crawl Space Moisture Barrier Benefit Your Home? 

There are a surprising number of benefits that a crawl space moisture barrier can introduce to your home. When you install a crawl space moisture barrier, you can make your crawl space healthier in all these ways. 

  • Reduce Humidity 

The ability to reduce humidity in your crawl space is an important one, and it’s one you should utilize any chance you get. Reducing humidity in your crawl space comes in a variety of ways, and there are many things you may need to do if you’re looking to reduce your crawl space humidity as much as possible. 

With a crawl space moisture barrier, you no longer have to worry about the humidity levels in your crawl space. The crawl space typically allows most of its moisture through the ground, even if you don’t have a dirt crawl space. That means a crawl space moisture barrier will allow you to maintain your crawl space’s healthy levels of humidity. 

  • Avoid the Stack Effect 

The stack effect is what happens when you have an entry for air from the crawl space and you have an exit for air from the top of your attic. Most homes have exits for air from the tops of the attic, which is how the original building crew likely built the attic. However, if you don’t close off the entries in the crawl space, you’re likely going to end up with the stack effect. 

This describes what happens when air comes into the crawl space from the outside. If it’s warmer than the rest of the air in your crawl space, it automatically starts to rise through the home. If it’s cooler than the rest of the air, it’ll warm up and then start to rise. Regardless of how long it takes, this will cause anything small enough to become airborne to come up through the entire home, riding on the air as it rises. 

  • Help Mitigate Any Radon Problems You May Have 

Radon is a problem many homeowners don’t do enough about. It’s unfortunately common for radon to permeate the entire home; because of the way a home utilizes its structure, it’s common for radon to become trapped inside the home, raising the radon levels inside the home while not doing so for unenclosed areas. 

However, if you’re able to install a very thick crawl space moisture barrier in the crawl space, you can use it as part of your passive radon mitigation system. Although it isn’t an active mitigation system and shouldn’t be your only defense against radon if you have active radon problems, it can lower the levels of radon in your home to a much more acceptable level.

wet insulation damp crawl space falling insulation.JPG (2)Matt 3 (1)

Before: Moisture that enters the crawl space through vents and soil can ruin insulation and also encourage mold growth and wood rot.
After: Covering the crawl space floor and walls with a heavy-duty moisture barrier eliminates moisture problems, makes the living space more comfortable and cuts heating & cooling costs.

Crawl Space Moisture Barriers


Because dirt crawl spaces are so prolific, it’s common for homeowners to wonder why they’re such a problem. However, dirt crawl spaces are a monumental issue, and you must tackle them as early as possible. 

  • High Levels of Crawl Space Humidity 

It’s common for high levels of crawl space humidity to flourish in a dirt crawl space that has not been fitted with waterproofing measures. That’s because the dirt will always be moist somewhere deep down. The water will move up through the dirt, causing high levels of humidity to occur in the crawl space, where it gets trapped. 

This can lead to several issues that range from inconvenient to expensive. A humid crawl space, for example, is likely to harbor mold and take on a musty smell. This mold can cause skin irritation and respiratory problems, but as the humid air circulates your home, it can also impact your energy bills. So, with mold spreading through your home, bringing musty smells and high energy bills, it’s clear that dampness is an issue worth thinking about. 

  • No Protection for Storage 

If you want to use your crawl space for storage, it’s probably a bad idea to do so when you have a dirt crawl space. Dirt crawl spaces provide no protection for anything you put down in the crawl space, which means it’s a space under your home that’s just taking up space without offering any benefits. 

Of course, if you were to use completely airtight storage like vacuum bags, a dirt crawl space could still be useful, but this severely limits what you can store in it. After all, the things most homeowners wish to store in a crawl space are those things that are used seasonally at most (Christmas decorations, for example) or that are very bulky.

When you install a crawl space moisture barrier, you’re ensuring that you don’t run into some common problems. A crawl space moisture barrier is necessary if you want to make sure you’re creating a healthy home. 

  • Avoids Moisture Through the Floor 

A crawl space moisture barrier, especially when you install it appropriately, helps you avoid moisture coming through a dirt floor. It traps the moisture on the outside and effectively creates a clean and dry bubble within your crawl space. That way, you don’t have to worry about the moisture causing high crawl space humidity and eventually condensation. 

By investing in a durable and high-quality vapor barrier, you will protect your home from persistent dampness as well as all the problems that this can bring. Some high-quality vapor barriers are even treated with mold-resistant chemicals to ensure that mold is kept firmly at bay no matter what happens. 

  • Helps Deter Pests 

Pests are one of the most frustrating things that can come in through your crawl space. If you have a dirt crawl space, it’s very easy for all sorts of pests, especially bugs and rodents, to dig up into your crawl space. By installing a moisture barrier in your crawl space, you are helping to reduce pests’ interest in your space. 

Of course, it will also make it harder for pests to enter your crawl space, especially if you cover your crawl space vents as well. However, if some pests do manage to gain access to your property, they will find that the space created by the barrier is entirely unappealing because of the lack of hiding spaces or food.

A 20-mil crawl space moisture barrier is recommended by Foundation Recovery Systems. It’s much thicker than the required minimum and even thicker than many contractors will recommend. Is it really important that you get a 20-mil barrier? 

  • Thinner Vapor Barriers Are Less Effective 

A 6-mil crawl space moisture barrier is typically the minimum requirement. However, this is the absolute minimum requirement, so it’s not the best option for your crawl space. This barrier thickness is well known for being easy to tear and not very effective, so it’s not a good choice unless your main concern is cost. 

A 10- or 12-mil crawl space moisture barrier, by contrast, will be much more effective than a 6-mil crawl space moisture barrier, as it’s about twice as thick. However, Foundation Recovery Systems doesn’t recommend this barrier because it’s still not as effective as it should be. All thinner vapor barriers are more prone to rips, tears, punctures, and general wear-and-tear. 

  • 20-mil Barriers Offer Better Benefits 

If you want a firm boundary that keeps your crawl space safe, a 20-mil barrier is your best option. With a 20-mil barrier, you don’t have to worry about whether you’ll break it when you use your crawl space. A 20-mil barrier is better and more effective than the 10- or 12-mil barrier and far superior to the 6-mil options. 

A 20-mil vapor barrier is the most commonly recommended by professionals because of its superior tear and puncture resistance. You will not have to worry about the vapor barrier tearing when you move over it. Likewise, this vapor barrier tends to be more resistant to mold and pest incursion, thereby providing a more complete and lasting level of protection.

The installation aspect of a crawl space moisture barrier is something that can trip some homeowners up. Contrary to popular belief, it’s not enough to just put down a barrier over the ground. You’ll run into problems if you try to install your own crawl space moisture barrier. 

  • DIY Installation Problems 

The installation process is extremely important when it comes to your crawl space moisture barrier. As a DIYer, you may not know what you can do to maximize your installation benefits. That can lead to serious problems down the line and even completely undo any benefits that your barrier could have offered. 

The most pressing risks when it comes to a DIY installation are damage to the vapor barrier and gaps. Both will have the same basic result, however; whether you tear the vapor barrier during installation or leave a part of your crawl space unprotected, moisture will get in. This will magnify the normal side effects of dampness. 

  • Professional Installation 

A professional installation through Foundation Recovery Systems will always be your best option for crawl space encapsulation. You’re taking an important step just by considering crawl space encapsulation, but a professional installation will make it even better. First and foremost, professionals have access to the best products – this means that you get more bang for your buck. 

Beyond this, however, you can rely on professionals to survey your crawl space for red flags and other warning signs which might indicate there are problems that your moisture barrier might cover up. They will also make sure that you get a high-quality and durable result.

What Does the Crawl Space Moisture Barrier Installation Process Look Like? 

When you’ve chosen to add a crawl space moisture barrier to your crawl space, you’ll go through a short process to ensure the barrier has the proper installation. Here are the main steps involved in the crawl space moisture barrier installation. 

  • Inspect the Crawl Space to Uncover Problems 

The first step a crawl space repair expert will take is to inspect the crawl space. Uncovering problems in your crawl space can help you understand exactly what you need to do to fix those problems. Even if you know you need a crawl space moisture barrier in your crawl space, the fact is that there may be additional crawl space concerns you need to mitigate as well. 

This inspection will help you understand exactly what your crawl space needs. You must get a crawl space repair expert to do this inspection. Although you can inspect your crawl space regularly to identify obvious problems, you should have an expert inspect the crawl space if you’re looking into official fixes. 

  • Add Additional Waterproofing Options 

Before applying the moisture barrier to areas like the crawl space floor, you may need to combine the crawl space moisture barrier with other waterproofing options. For example, you might end up adding an interior drainage system, sump pump, dehumidifier, or covering crawl space vents. These other waterproofing options make it even easier for you to manage your crawl space’s water problems. 

Most crawl spaces have some water concerns, which is why it’s so important for you to look into waterproofing options. However, a crawl space repair expert will be able to give you more information on which waterproofing options will be best for you. Talking to a Foundation Recovery Systems expert will give you more information about the waterproofing process. 

  • Install a Heavy-Duty Crawl Space Moisture Barrier 

Next up, this expert will install the moisture barrier. There are many different ways for an expert to install a crawl space moisture barrier; the specific installation process may depend on your unique crawl space needs, the height of your crawl space, and whether or not you have a crawl space moisture barrier that will be effective for your home. 

In most places, a 6-mil crawl space moisture barrier is the minimum necessary thickness to ensure your building is up to code. However, that doesn’t mean the 6-mil crawl space moisture barrier is the best option for you. Foundation Recovery Systems uses the 20-mil CrawlSeal™ crawl space moisture barrier in its encapsulation process, ensuring you have the maximum protection available. 

Make Your Crawl Space Moisture Barrier More Effective with an Expert’s Help  

If you’re looking for a good way to maintain your crawl space, it’s a good idea to consult an expert first and foremost. A crawl space moisture barrier is a great addition to your crawl space if you’re looking to cut down on crawl space humidity, but it won’t work very well unless you have an expert who can help you install it properly. 

This is exactly why it’s so important to contact a crawl space repair expert. When you install a crawl space moisture barrier, you’ll end up with plenty of benefits, especially over trying to DIY a solution. A crawl space moisture barrier is an incredibly important part of a home, and a Foundation Recovery Systems expert can help you ensure you set it up appropriately.

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