Humidity Problems in Basements

      

Water is insidious. An underground spring may be blamed for your flooded basement; the water actually may have originated at a leaky gutter and funneled its way through the top of the foundation wall into the basement. Therefore, stopping a leak can involve more than pushing a wad of hydraulic cement into a concrete crack. The first step is to define the problem: is the basement or crawl space damp or wet? Is the dampness caused by humidity, or is it a water problem such as running water from the walls or floor? When does the wet condition occur? Always, during the summer months, during a rainstorm, after a rainstorm?

Please read this 3-part article before you buy any leak-fixing tools and materials. The time you spend up front can save you plenty later.

TREATING HUMIDITY:
Humidity is a dampness problem, rather than an open running water situation, and it usually occurs during the summer months, except for some southern areas, such as Florida and the Texas Gulf, where humidity is more-or-less a year-round problem that results in a chronic case of mildew.

In existing basements-
Moist air tends to move toward drier air, which can occur with air moving from a damp basement to the drier area upstairs. The simplest way to dry out a damp basement is to use a dehumidifier. However, this is assuming that there are no structural causes for the humidity.

If there is water leakage in the basement that is not serious, cracks must be cleaned with a cold chisel and sealed with hydraulic cement and then the walls and floor should be covered with a water proofing compound that you can buy at most home centers and building material outlets and paint specialty stores.

All downspouts should be directed into plastic or concrete splash pans that direct the rainwater away from the foundation. Ordinary concrete and concrete blocks, if your home sets on this type foundation, are not waterproof. The best way to avoid water, which creates humidity, is to direct the water away from foundation walls.

Cover cold water pipes with pipe insulation to pre vent condensation of water on the pipes. This condensation can cause a very high humidity problem.

Also, make sure that your washing machine in the basement is draining properly and that your clothes dryer is vented.

New basements-
If your home is being built or it is a brand-new home, or a basement is built for a room addition, you can ensure a dry basement by applying a continuous layer of polyethylene sheeting on the outside of the foundation walls before backfilling. This is detailed on Page 4.

The same vapor barrier material should be placed on the ground before the basement floor is placed. The polyethylene comes in rolls 10 to 20 feet wide, and the strips applied to the foundation should overlap at least 4 inches. If the basement is built in an area where there is a high water table, tiling must be placed on the outside of the footing with a lead to a drain from the tile to a lower spot in the yard area.

Crawl spaces-
Where the soil frequently is wet, crawl spaces are subject to excessive humidity that can migrate up through the floor into the house. Another suspect area is where a porch is connected to the house and the bottom of the porch is enclosed. This creates a "crawl space" of sorts, and the humidity created here can get into your home causing trouble.

Generous ventilation sometimes will get rid of the moisture-laden air. Vents in the foundation, located to take advantage of a prevailing wind, is one method used. The area of all vents should be equal to 2 square feet. For each 100 lineal feet of foundation perimeter plus one half percent of the crawl space area.

However, foundation vents alone sometimes are not large enough to provide the needed ventilation, so an exhaust fan is installed, see illustration. The lower end of the ducting is supported above the ground and the exhaust can be run to the out side through the floor joist or the header joist that runs at right angles to the floor joists.

To control ground moisture, place a layer of the sheet plastic on leveled soil. Over this, smooth a 3 inch layer of sand. Waterproof the outside of the foundation wall and install drain tile around the footing to drain away any water that might rise higher than the floor of the crawl space.

An alternative would be sealing the undersides of the floor joists with a vapor barrier if water lines and ducts for heating do not make this impractical. If any ducts or pipes do pass through the vapor barrier, they are sealed with duct tape to the barrier to assure a moisture-tight surface. Seams in the plastic sheeting are overlapped and stapled to the joists lengthwise, then further supported by nailing lath or other strips of wood to the joists over the seams of the plastic.

New home interiors-
If you have just moved into a new home, expect to find humidity created by moisture in new building materials, especially plaster, that is released very gradually for at least a year-sometimes two years. To minimize this humidity, change the air frequently by using fans and opening windows. A dehumidifier will help eliminate moisture faster.

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