Warning Signs of Crawl Space Humidity Problems

Most folks don’t spend much time thinking about their crawl space – something about “out of sight, out of mind.” But just because you’re not thinking about it doesn’t mean it isn’t affecting your home and health.

We’ve put together the top 10 warning signs that your crawl space may be excessively humid, as well as a list of the problems associated with high crawl space humidity. If you suspect that your crawl space is excessively humid, a vapor barrier is a long-lasting and cost effective solution to the problem!

Warning signs of humidity issues in your crawl space

Diagnosing humidity in your crawl space can be a bit of a challenge since most homeowners don’t spend much time crawling around under their homes. Some of these symptoms will require a bit of spelunking, while others can be detected without even needing to leave your living room.

If you notice any of these signs you likely have a humidity problem that needs to be addressed!

Wet walls in crawl space

Everyone knows crawl spaces are damp… right? Well, there is a difference between cool and slightly humid and “the walls are literally dripping.” The former is usually fine, while the latter is a warning sign of problems to come!

Painted surfaces in your crawl space are peeling

Under normal conditions painted surfaces in your crawl space should remain in good condition for many years. High humidity, however, can cause paint to begin to bubble and peel as materials swell or warp.

Humidity reading

Condensation on HVAC vents

Your HVAC vents carry cool air to your home and their temperature differential rapidly causes humid air to condense. A small amount of condensation may not indicate a severe problem, but is definitely a warning sign to keep an eye out for.

Rotting floorboards, wood or insulation in crawl spaces

Any sign of rotting wood or insulation is a huge red flag. This means that you’ve had a humidity problem for some time and need to act fast before the problem results in structural damage.

Mold growth

Mold and mildew need humidity to grow and thrive. If your crawl space is humid enough to grow mold, then you’ve got excessive moisture that needs to be handled! This problem can rapidly turn into a real headache as mold remediation is expensive and time consuming.

Lots of bugs/pest activity

Cockroaches, spiders, termites, and other creepy crawlies love damp conditions. If you look into your crawl space and the crawl space floor is rippling with motion – well – you’ve probably got a moisture problem in addition to a bug problem!

Sagging Floors

If you’ve noticed that your floors are sagging – particularly more on the ground floor compared to your 2nd floor – then you may have a humidity problem brewing! We recommend taking a peek at your home’s crawl space to see if you notice any other signs of humidity problems.

Your home is always humid, even after running air conditioning

When running your AC makes your home more clammy than refreshing, you’ve got an indoor humidity problem. This can be the result of a variety of causes, but one serious one to consider is excessive crawl space moisture making its way up into your living space.

Damp or musty smell in home that doesn’t go away

Persistent musty smells without a clear cause should be investigated. Oftentimes these smells are caused by mold or mildew growth in your crawl space which has gone on undetected!

Standing water in crawl space

If you’ve never spent much time under a house you might be forgiven for thinking that standing water in a crawl space is normal. Well – we’ve got news for you: it’s not! Standing water leads to mold, water damage, and insect infestations, and is a clear sign that there is too much moisture in your crawl space.

How can humidity in my crawl space affect me?

The ideal humidity for your crawl space is between 45 and 55%. Levels above this can damage your home and cause health problems.

Foundation Issues

As shocking as it sounds, humidity problems in your crawl space can lead to a cracked foundation! It isn’t the moisture in the air that’s the problem, but instead is the water content in the soil around the foundation. In the winter, this water freezes, expanding in the process. This expansion can exert incredible pressure, shifting or cracking foundation pilings.

Humidity reading

Structural Issues

When kept dry, your home’s structural timbers can easily last a century, however this lifespan is vastly reduced in high humidity conditions. Rot can cause floors to sag and seriously weaken your home’s floor joists.

Comfort Issues

If your crawl space is humid there is a good chance your indoor air will be too! This can cause a wide variety of problems – including uncomfortable clammy or stuffy feeling air.


Mold is one of those innocuous house problems that is legitimately scary. From minor concerns like hard-to-eliminate musty odors to the potentially severe health issues caused by mold spores, mold is a serious problem. Getting rid of mold is an expensive and time consuming task, so your best bet is to prevent it from forming in the first place!

Pest Infestations

Bugs love humid crawl spaces – so much so that if you allow your crawl space humidity levels to stay high for too long you risk a severe insect infestation! Every sort of undesirable critter from cockroaches to termites is happier when your crawl space is moist – and eventually these infestations will spill over into your living space!

What can I do to prevent excess humidity in my crawl space?

There are two primary ways of dealing with humidity in a crawl space. The first is by installing a vapor barrier, reducing the surface area that moisture can enter from, and allowing ventilation to take care of the rest. The second is by fully enclosing the crawl space and using a sump-pump and dehumidifier to remove moisture as it accumulates.

Vapor Barriers

This is our recommended method for handling crawl space problems. Vapor barriers effectively manage moisture in the vast majority of cases, are affordable, long lasting (20+ years), and have no mechanical parts to wear out or fail.

Vapor Barrier installed in basement

Too Much Moisture? Act Fast!

If you suspect that your crawl space has a humidity problem the best time to act is now. Wood rot and mold can take hold quickly, leading to structural damage, reduced indoor air quality, and health problems.

We provide free inspections where we assess your crawl space for signs of excessive humidity and make suggestions for remediation. Don’t wait for the problem to get out of hand, let Dragon Vapor Barriers protect your castle!