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Crawl Space Encapsulation and Vapor Barriers for Damp Crawl Spaces

Apr 9, 2012 • By Matthew Stock with Ben Shachter.

Crawl Space Encapsulation and Vapor Barriers for Damp Crawl Spaces


A crawl space is often wasted space if a dirt or gravel floor makes it unusable or inconvenient for the storage that every homeowner needs.  It’s even worse if the crawl space contributes dampness to the home or allows costly heating or cooling to escape.  We are often called upon by homeowners to turn their unfinished crawl spaces into dry, usable areas that can be put to practical use.

In Chicago, as in other parts of the country, many homes are built with full or partial crawl spaces instead of full basements. Quite often, the original builder will leave a crawl space with only a dirt floor or, at best, a layer of gravel over a thin plastic vapor barrier.  Not only are these crawl spaces unusable but they can allow moisture into the home, leaving the possibility of mold growth, and are a prime culprit in heat loss and cold air infiltration.

Traditionally a concrete floor has been the method of choice to seal off a crawl space where no floor surface was installed at the time of construction.  Modern improvements have led to the development of a crawl space encapsulation system as an alternative to the concrete flooring system.  Each has its advantages and one or the other will solve the crawl space problem in almost any home.

Let’s take a closer look at each system:

Concrete Floor

Pouring a concrete floor in an unfinished crawl space is an old standby that is still the best solution for some homeowners.  Typically, the concrete is pumped into the area and spread over a polyethylene vapor barrier (3 mil. to 6 mil. in thickness).  The resulting floor is usually 2” to 3” thick with a rough “float” finish because there is no need for a smooth finish floor in a crawl space – an unnecessary expense.

The main benefit to a concrete surface in a crawl space is a rigid, durable floor, especially useful if the homeowner will be in and out of the crawl space often.

Crawl Space Encapsulation Systems

Crawl space liners or encapsulation systems are a modern solution for unfinished crawl spaces as they cover and seal both the floor and wall surfaces.  Heavy duty polyethylene (12 mil. to 20 mil. in thickness - 3 to 6 times thicker than typical vapor barrier) is laid directly on top of the entire dirt or gravel floor surface.  Simple liner systems will just extend this same vapor barrier to the top of the crawl space wall —   U.S. Waterproofing’s crawl space encapsulation system includes a semi-rigid plastic underlayment atop the gravel/dirt floor and insulation on the wall surfaces to increase energy efficiency in the home.

Benefits of the encapsulation system include:

  • Moisture reduction
  • Better air quality in the home
  • Reduced heating and cooling costs
  • Protective barrier against insects
  • A clean, bright, dry space for storage

Whether the homeowner chooses to install a complete encapsulation system or just a concrete floor, water seepage in the crawl space indicates that an interior drain tile system should also be installed.

Installing either a concrete floor or a crawl space liner system will increase the usable area of your home, which can result in a higher resale value.  The crawl space encapsulation system offers the additional benefits shown above and typically can be installed for less than the cost of pouring a concrete floor.

With more than 50 years of experience in both basements and crawl spaces, U.S. Waterproofing can tailor a solution to meet your needs. Contact us for more information.

Tags: crawl space encapsulation, crawl space vapor barrier, crawl space concrete floor, damp crawl space

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