Crawlspace Moisture And Evaporation

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The Water Cycle

Moisture problems in crawlspaces are tightly connected to the simplest natural cycle on planet earth: the hydrologic (water) cycle. The hydrologic cycle refers to the continuous movement of water in nature. The principle is very simple and can be described in a few words like: evaporation, condensation, precipitation, infiltration, runoff and subsurface flow. What does this actually mean? Heat from the sun makes water evaporate from the oceans, seas, lakes, rivers and soil which forms vapor. As vapor, millions of gallons of water rise into the atmosphere, meets cold air and condenses, or cools down to become water again. This usually happens when water droplets gather and form into clouds. Traveling high in the atmosphere, clouds become colder and force the water droplets to join together and fall to Earth; this is known as precipitation. Rain falls into the rivers, lakes, seas and oceans, but can also infiltrate soil which forms subsurface flow which helps lakes, rivers, and streams stay full.

Nature’s Hydrologic Cycle Can Cause Excess Moisture

The simple phenomenon of the water cycle also effects what happens in the crawlspace of a house. Evaporation and condensation are the two parts of the cycle that represent the biggest problems to homeowners. The difference in the temperature of the crawlspace and that of the outside air (the crawlspace is always warmer) causes the soil under the house to become humid, meaning the more humid the soil, the bigger the problem. When water vapor from the soil meets the cool air from outside, the cool surfaces of the crawlspace walls and beneath the flooring, condenses which opens the door for excessive moisture to form. High percentages of moisture in the crawlspace can cause the walls of the foundation to move, drywall to crack and eventually cause structural damage to the house.

High Moisture Levels – A Potential Nightmare

High percentages of moisture within the crawlspace can encourage molds to grow. Molds cannot destroy the structure of the house but are an indicator of much bigger problems. Molds only occur when the percentage of moisture is higher than 70%. Molds are microscopic fungi that live on the surfaces of moist wood. Although they cannot affect the wood directly they increase the capacity of wood to absorb moisture. High moisture levels are ideal for wood decay fungi to grow and can attract insects. Carpenter ants are the most common insect that are attracted to moist wood. They do not eat wood but they do use it to create nests by burrowing within the wood thus weakening the wooden structure of the house. When weakened, the wooden structure is prone to cracks which can seriously damage the building. Another group of insects who love moisture and attack wooden structures of houses are termites. Termites feed directly on the wood consequently weakening the wooden structure of the home. Like carpenter ants, termites can also seriously damage the building causing a genuine nightmare for the homeowner.


For solutions to moisture problems and the insects they attract check out our other blogs. If you find that you have major problems and don’t know what to do, PESTOUT can help you find the answer. Always remember to routinely check your foundation, basement, and crawlspace to ensure they are dry and in good repair.