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Crawl Space Vapor Barrier

Charlotte, NC is one of the rainiest cities in the nation. If you don’t have a proper waterproofing solution in place, then your crawl space will be wet and humid.

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Although the underside of your home is usually never seen or thought about, the conditions of your crawl space matter more than you think. It’s important that everything is kept dry to avoid foundation failure and costly repairs. Water is a persistent substance, and you can’t prevent it from entering a crawl space with just anything. A crawl space vapor barrier is needed to truly protect your foundation and your home. Luckily, Dry Pro offers CrawlSeal™, one of the most durable vapor barriers on the market.

encapsulated crawl space job

What Is the CrawlSeal™ Crawl Space Vapor Barrier? 

Whether you have a dirt crawl space or a cement crawl space floor, water will find a way to enter the foundation. The only way to stop the water from entering the crawl space is to install a vapor barrier. A vapor barrier is a sheet of plastic that is applied all around the crawl space, including the floor, support posts, and walls. Vapor barriers completely encapsulate the crawl space and prevent water from entering the space. 

The vapor barrier itself is made of polyethylene, which is a thermoplastic polymer. This special kind of plastic has molecules that are denser than normal plastic, which makes it completely impenetrable. CrawlSeal™ specifically is made of a thick, 20-mil liner, and it has polyester cord reinforcement. It’s three times thicker and more durable than builder-grade vapor barriers. 

Besides keeping the water out of your foundation, it also keeps water vapor out. Water vapor from the outside can get into the crawl space through the soil and the concrete walls. Concrete is a permeable material. It’s porous and water vapor easily gets through, in turn increasing the humidity levels in your crawl space. 

CrawlSeal™ does not need to be replaced—it is a permanent solution to your foundation’s humidity and water problems. Here are some of the special benefits that you get by installing CrawlSeal™: 

  • 25-year warranty 
  • Year-round installation 
  • Anti-microbial properties 
  • Does not tear or flake off 
  • Reduces energy costs by 20% 
  • Compatible with other waterproofing solutions

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How Is CrawlSeal™ Installed? 

Crawlseal crawl space encapsulation install ExtremeBloc

Installing CrawlSeal™ is incredibly simple. Here’s how it works: 

First, specialists need to clean the crawl space and repair any structural damage. This isn’t done on the spot; the damage will have been assessed during the initial inspection and the workers will have all the tools they need to set up the crawl space so that everything is ready for application. 

If there are any other waterproofing solutions that need to be installed, then these will be taken care of before the vapor barrier is placed. In fact, you won’t be able to install the vapor barrier unless a perimeter drain system is installed first. This is crucial for collecting water that drips down the wall. Without this drain, the water would simply accumulate behind the vapor barrier. 

They will then measure everything, and CrawlSeal™ is cut into multiple sheets. The sheets are then applied to the walls, floor, and columns of the crawl space in a way that makes them overlap with each other, so no area is left uncovered. The overlapping seams are then fastened with plastic ligatures that are drilled in. Because they are fastened so securely, the sheets never fall off and remain attached to the crawl space permanently. Once that is done, other crawl space waterproofing and repair solutions, such as insulation panels and a dehumidifier, can be installed. Don’t forget that you can always contact us for an annual maintenance checkup. Depending on what you install in the crawl space, there may be certain components that need to be replaced annually to ensure that everything is in tip-top shape.

How to Tell If Your Crawl Space Needs a Vapor Barrier

There are many straightforward signs that you can check for that indicate that you have a foundation moisture problem. You may not see the effects these signs have on your home, but they will manifest themselves eventually. Here are some of the more common problem signs to look out for:

Standing Water 

The very first thing you should look for in your crawl space is standing water. Any puddles that form, no matter how small, indicate that your crawl space needs a vapor barrier. The best time to check for standing water in your crawl space is during the summer, which is when it rains the most in Charlotte. 

If you have any plumbing issues, then you need to check the crawl space as well. Your crawl space is where a lot of the plumbing pipes are found, so if something is unusual about the plumbing in your home, there might be a leak somewhere. 


Mold thrives in damp, dark places, so it usually grows in crawl spaces. When checking for mold, make sure that you check the concrete thoroughly. The growth often stains the concrete with green and black colors, which can be difficult to spot unless you have a flashlight. 

Wood Rot 

Wood rot is a fungal infection that eats away at the wood. The type of fungus that grows on wood tends to stain it with green, white, gray, yellow, or black. Red dust spores are also common in some cases. Wood rot deteriorates floor joists by either softening them or breaking them apart. This hinders their ability to support your floor, causing a bouncy, sagging floor. 

moldy crawl space

Condensation is the opposite of evaporation. Instead of liquid turning into water vapor when it gets hot, water droplets form from the moisture in the air when it gets cold. Water droplets tend to appear on HVAC ductwork, pipes, and concrete walls, since these spots tend to be colder than the crawl space itself, creating the perfect temperature needed for condensation to occur. 

Condensation is a sign that there is too much moisture in your crawl space. Without a vapor barrier, water vapor will continue to permeate through the space and cause water droplets to form all around your foundation. 

High Energy Bills 

It may not seem like it, but your high energy bills might be caused by your wet crawl space. This is due to the stack effect, a phenomenon that describes how air circulates in a home with a sub-level. During the summer, warm air enters the crawl space. The air in the crawl space then rises into your home since warm air is lighter than cold air. 

The problem with this is that the constant flow of warm air interferes with your AC’s ability to keep your house cool. You might be able to feel this temperature problem, which might lead you to leave your AC on for longer and keep it running on a lower setting. All this does is make the unit consume more energy and raise your energy bills. A crawl space vapor barrier prevents warm summer air from entering the space and can lower your energy costs by 20%. 

Strange Smells 

The stack effect doesn’t just bring up warm air into your home. A wet crawl space usually smells terrible because of the humidity, mold, insects, and dirty water. Because of the stack effect, all those odors make their way up to your living space. If you often get inexplicable foul odors wafting into your home (especially during the summer), then they could be coming from your crawl space. 


Efflorescence is often confused for mold on concrete, but it’s far from it. This phenomenon is a white stain that appears on concrete when the moisture in the structure displaces the salt. As the water rises to the surface, it brings with it all the salts and minerals in the concrete. The result is a cluster of salt along the surface. 

While efflorescence isn’t as dangerous as mold, it is a clear sign that your concrete is getting saturated with water. This is usually from the surrounding groundwater, but it could also be from flooding.

How Does Water and Humidity Get Inside My Crawl Space? 

Water can get into crawl spaces in many ways. A vapor barrier is the only solution capable of stopping the water because it’s the only solution that protects all the structural weaknesses a crawl space has. It is through these weaknesses that water gets in. 

Vents and Openings 

Any vents, holes, or openings in a crawl space will lead to flooding and leaks. Although some crawl spaces are designed this way, they are not meant to have vents. The reason they do this is because of outdated building codes and tradition. A crawl space vent cover is needed to seal off the crawl space, and any holes should be closed off before the vapor barrier is applied. 

The Soil 

If you have a dirt crawl space, then water and moisture is capable of permeating through the soil. Underneath the soil on your property, there is an invisible line known as the water table, which indicates where the zone of saturation starts. The zone of saturation is the area underground where the soil is permanently saturated with groundwater. 

The depth of the water table varies all throughout the city, but many homeowners have an extremely shallow water table. When it rains, the water seeps through the soil, and the water table rises as more water accumulates underground. This often can result in flooding, even when your crawl space is seemingly closed off. 

Cold Joints 

Once concrete begins to harden, if a new batch of cement is poured on it, the new batch will not stick. There will be a slight gap between the new batch and old batch; on the joints that connect the walls and floor, this is called a cold joint. Because the walls and floor of your crawl space aren’t properly connected, water is easily able to seep through the cold joints and enter your crawl space. 

Unfortunately, this is something that is out of the homeowner’s control, since it has to do with any delays that may have occurred as each batch of concrete is poured. Luckily, this problem can be fixed with a vapor barrier.

Crawl Space Vapor Barrier


Why DIYs Don’t Work 

DIYs don’t work mainly because of the materials homeowners have to work with. Many DIY pages suggest using normal plastic sheets for crawl space encapsulation. However, normal sheets don’t work because they are too thin and can easily be torn up. Even if you buy a product that advertises itself to be a vapor barrier, many of these are poorly made and don’t do a decent job of blocking out water and water vapor. 

Besides, it’s not just the vapor barrier you have to work with. A perimeter drainage system is required if a vapor barrier is to be put up. Charlotte, NC is one of the rainiest cities in the Southeast. Water often permeates through the walls and leaks into the crawl space. A perimeter drainage system like CrawlDrain™ is needed if that water is to be collected and pumped out. Without one, the water will accumulate behind the vapor barrier. 

What You Can Do Instead 

You can trust your local foundation experts to install a vapor barrier in your crawl space. It saves you time, gives you peace of mind, and, most important of all, keeps you out of danger. If your crawl space is experiencing structural damage after years of exposure to water, then you don’t want to be there installing anything. DryPro crawl space experts have the experience to deal with all kinds of structural damage safely, so entrusting the installation to them is for the best.

Crawl spaces are typically built with vents, but they allow water to flow into the foundation. Vent covers can help with this problem, but they shouldn’t be considered the only solution. 

What a Vent Cover Does 

Crawl spaces are built with vents because it was once believed that they help with air flow in the crawl space. Now, construction workers understand that crawl space vents are a detriment, as they allow water to flow into the crawl space, flood the foundation, and increase its humidity levels. The solution to this is to cover up the crawl space vent with a vent cover. 

Many homeowners believe that this is enough to “encapsulate” a crawl space, but this isn’t the case. Encapsulation doesn’t just mean closing off any openings in the crawl space: it means making it so that no moisture is ever able to seep through. This isn’t limited to just water, as water vapor is something that you need to be mindful of. 

What It Doesn’t Do 

A crawl space vent cover is not capable of stopping water vapor from permeating through the walls. Concrete is porous, so any moisture from the outside will still manage to get through. The same thing happens if you have a dirt crawl space. The moisture from the soil rises into the crawl space, effectively raising the humidity levels. 

Only a vapor barrier can stop both water and water vapor from entering the crawl space. A vent cover only covers up one area of the space, but it can’t cover up everything, especially given how good water is at leaking through foundations. However, that doesn’t mean that you shouldn’t install a vent cover (one is needed if the vapor barrier is to be set up too), it just means that both are required if you want to keep your crawl space fully dry.

Vapor barriers play a crucial part in protecting your foundation. Charlotte, NC has humid subtropical weather, meaning that there’s a lot of rain and humidity for the better part of the year. Without the right waterproofing solutions in place, your foundation will deteriorate thanks to how destructive water can be. A vapor barrier helps mitigate the damage, but it’s not all that’s needed to stop foundation settling. 

What a Vapor Barrier Can Do 

A vapor barrier keeps water out of your foundation. This helps prevent soil erosion, especially if you have a dirt crawl space. Without a vapor barrier, the soil around the support posts in the crawl space would erode, causing settling, which affects the entire house. Vapor barriers also prevent the materials in the crawl space from getting torn apart from the freeze-thaw effect. 

How to Stop Foundation Settling 

Besides a vapor barrier, you will need a crawl space sump pump, a perimeter drain, and a dehumidifier. All these things work together to protect your crawl space, prevent foundation deterioration, and keep your home healthy. A vapor barrier works wonders on its own, but without the other waterproofing solutions, your crawl space is vulnerable to things like condensation and frost heave damage. 

Besides just making sure that your crawl space can handle water, you also need to make sure that as little water as possible is flowing towards it in the first place. You can do this by making certain alterations, such as pointing your downspouts away from your home or extending them. Make sure to also watch for clogging, especially during the fall and winter, when drains get clogged due to mud and leaves or they simply freeze over.

Call Dry Pro for Crawl Space Waterproofing and Repairs 

Dry Pro is an award-winning, locally-owned foundation repair company that serves Charlotte, NC. We are known for our friendly service, thorough inspections, transferable warranties, and flexible financing options. 

If you are interested in crawl space encapsulation, then don’t hesitate to call us or fill out our online contact form to schedule a free inspection. Our certified field expert will give you a same-day quote and a better understanding of what your foundation needs to stay structurally sound.

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