Crawl Space Moisture Control Explained:
Fixing Damp Wet Crawlspaces
As an engineer, I’ve been installing the best crawl space moisture control solutions, for the past 7 years. I’ve literally seen thousands of crawl space moisture issues and have been able to fix them all.
In this guide, I’ll be sharing the basic principles that can save you from doing the wrong thing and wasting money on the wrong solutions. If you’d just like to have our Expert Advisors inspect your home and provide recommendations, click here for a free inspection and estimate.
Sources Of Crawl Space Moisture
There are only 3 main sources of moisture in a crawl space:
- Moisture from humidity outside
- Moisture from the damp, wet ground
- Moisture from groundwater and flooding
If your home is exposed to 2 or 3 of these sources of moisture, you’re at risk of having moisture problems. The goal is to eliminate the sources of moisture, strategically, to achieve your goals.
Effects Of Crawl Space Moisture Exposure
- High wood moisture content
- Softened wood framing
- Mold and fungal growth
- Sweating ductwork and pipes
- Wood rot on joists, beams, subfloor, etc.
- Compression and shrinkage
- Bowing and warping of wood framing
- Musty smells and odors
- Wet falling fiberglass insulation
- Cupping hardwood floors
Controlling The Sources Of Crawl Space Moisture
The first and most important source of crawl space moisture to eliminate, is groundwater and flooding. If you have water intrusion in your crawl space, no other solution can work properly. Worse, if you do have a great vapor barrier or crawl space encapsulation, it can hold water like a swimming pool liner with a flooded crawl space.
The best solutions to eliminate crawl space flooding are drainage systems including french drains, sump pumps, and sometimes sand. With a well-designed system, we fully guarantee to prevent crawl space flooding with these reliable, time-tested solutions.
The second most important source of moisture to eliminate, is moisture from the earth. The damp ground constantly releases moisture vapors into the air, contributing to a damp, wet crawl space.
The best solutions to eliminate moisture from the damp ground are vapor barriers and crawl space encapsulations. Technically, crawl space encapsulations are just vapor barriers that seal 100% of the ground, around the piers, and all the walls. There are many other benefits of crawl space encapsulations too.
The last critical source of moisture to eliminate is moisture from the humidity outside. With vented crawl spaces, as the weather changes outside, so it does under the house. In the summer, the warm humid air outside can spike crawl space moisture issues.
To fully prevent moisture issues, you must seal the foundation vents, seal the crawl space access, and install a dehumidifier. This is called an unvented, sealed, or conditioned crawl space. Our Dry Space Crawl Space Encapsulation is guaranteed to eliminate ALL moisture from outside humidity and the damp ground.
Options For Crawl Space Moisture Control
French Drains and Sump Pumps – French drains should capture all water intrusion inside the crawl space to completely prevent flooding. All water should be automatically removed from the crawl space with a sump pump drainage system.
Vapor Barriers – thick polyethylene sheeting can control the moisture from the damp ground. For the most cost-effective solution, 6-mil poly is OK. For the best long-term moisture control, we recommend a thicker 12-mil or 20-mil vapor barrier, with 100% ground coverage, properly secured and sealed.
Crawl Space Dehumidifiers – a dehumidifier can clean and dry the crawl space air. For the best performance, the crawl space should be tightly sealed and cleaned, without obstacles.
Crawl Space Encapsulation – a sealed, conditioned crawl space encapsulation can completely control crawl space moisture, throughout the year. A dehumidifier is required.
Crawl Space Fans – fans are useful to circulate air. In our experience, they do more harm than good for most homes. Unless you’re trying to circulate air in a restricted space or move the dry air from a dehumidifier, fans do not eliminate moisture.
Inspecting Your Crawl Space For Moisture
It helps to have a trained eye when inspecting a crawl space. Signs of dampness, moisture, or condensation change throughout the year, so we recommend having our trained experts help assess your crawl space and help to remedy any concerns you may have.
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