A crawl space, also known as a finished basement, is an unfinished, empty, narrow unoccupied space in a construction, usually between the basement floor and the first floor level. The word ‘crawl’ is derived from the fact that it is difficult to walk through a crawl space, with the walls and ceiling acting as steps. A crawl space may also be described as an unfinished basement, as it is not always finished basement that people refer to, but may only be a part of a completed home. This type of space does not necessarily have sub-roomification, as it is a part of the construction and not necessarily part of the living area of the building.

When a crawl space becomes too full of humidity, mildew and mold, it becomes a breeding ground for mould, dust mites, termites, radon gas, water damage and moisture-causing organisms. A damp crawl space may also contain harmful chemicals and waste materials such as asbestos, lead paint and discarded automobile tires. It is easy to tell if a crawl space has problems with water infiltration or excessive moisture. Check for signs of subsurface drainage and find water-logged drywall or damaged masonry around the ceilings, walls and floors, especially in the foundation. Excessive moisture can cause warping, buckling and rotting of the building materials, and this will make the foundations more susceptible to failure, especially in earthquakes.

An effective solution for crawl spaces is encapsulation. The process of encapsulation involves spraying a water-resistant coating of polyethylene onto the walls and floor, as well as sealing the seams between the walls and ceiling using rigid foam tape. The rigid foam tape is then connected to a water-proof membrane attached to the ceiling above the liner system. A water-resistant, odor-free encapsulation membrane is another method of insulating a crawl space by using a vapor barrier. This membrane will keep most smells out of a space, which is especially important when a building is being constructed and is adjacent to an occupied home or other occupied space.

Condensation is a problem with basements because of the relative humidity and temperature. Basement walls are often sealed with mineral wool or insulation board. These products prevent moisture from penetrating the surface of the wall and condensation from occurring. Moist air tends to rise so the water in the basement flows upward into the attic or crawl space. This process causes the relative humidity to increase. When basement walls are sealed, the increased relative humidity is replaced with indoor air.

Air ventilation is another problem with basements that cannot be remedied with typical materials for walls and roofs. Many basements in commercial buildings are poorly ventilated and suffer from condensation and mold buildup due to inadequate ventilation. Even when ducts and plumbing are using to provide ventilation to the crawl space, the typical materials used (cement, tile, sheet rock) do not filter enough air for good ventilation.


Mold, mildew, black mold and wood rot are all symptoms of moisture problems in a crawl space that must be cleaned up and repaired. If your crawl space has the potential to hold water and is unventilated, you need to find a solution now. By sealing and encapsulating your basement, you can stop the growth of mold and pests, and also provide a healthier living environment for you and your family.

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