Before you start digging up around the foundation of your house or wondering if you’ll need a bank loan to pay for waterproofing your basement, find out where the water’s coming from. The accepted process for this is to tape a twelve-inch piece of aluminum foil to the damp basement wall, sealing it tightly. Check the foil in a few days. If the outside of the foil is damp, condensation is the culprit. If the inside of the foil is wet, you have a seepage problem.
If condensation is the problem, improving ventilation should help. Heat in the winter and air conditioning in the summer will reduce dampness and remove humid air. Check to be sure all basement windows are closed in wet weather. Examine water pipes for any leaks and repair them. Insulate cold water pipes to avoid sweating. A dehumidifier may also help to reduce dampness. You’ll want one that’s heavy duty, so expect to pay about $250.
If the problem is seepage, look first for the obvious. If you have basement window wells, see if water is settling there and seeping in around the windows. Install window well covers. Gutters and downspouts that are clogged with leaves and twigs and prevent water from draining away from the house are a common cause of water seeping into the basement. Extend downspouts ten feet from the house. If there are no gutters or downspouts, install them.
Shrubs and flower beds too close to the foundation may reduce ventilation and allow moisture to collect. Trim or remove plantings. If the lawn is sloped toward the house, rain water or melting snow will drain toward the foundation, seeping in through any tiny crack. Slope the land away from the house or install drainage that will divert the water ten feet away.
If none of these problems seem to be the reason for your wet basement, then ground water is getting in though cracks in the basement wall or floor. You have several options. An interior drain that runs along the inside of the basement walls, like a baseboard, and sends the water to a sump pump will remove the water but not solve the basic problem.
Do-it-yourself kits run from $250 for enough materials to cover twenty feet to around $1000 for ninety-six feet. That comes out to $10.50 to $12.50 per foot, plus your time and energy. Professional installation will be about twice the cost.
Seal foundation cracks from the outside with epoxy, polyurethane, or rubberized filling compounds or hydraulic cement. Cost for these products run from up to $7 a tube of caulk to $12 for a quart of sealer. Water proof paint expands into any cracks and seals them, if applied properly.
Painting over any existing paint is usually not recommended but check the label for instructions on the product you choose. Allow up to $25 a gallon for this type of sealing paint. If excavating around the perimeter of the foundation, installing a waterproof barrier, gravel and drains seems to be in order, plan on no less than $5000, it could be much more. But this should be a last resort and only for extreme problems.
There is also a complicated system of drains, gravel, and sump pumps that remove water before it enters the basement. This involves jackhammers to break up the floor and can cost anywhere from $2000 to $4000. Sodium bentonite or a similar substance can be used as filler between the foundation and the soil. It swells when wet, thus filling any cracks in the foundation. Available in fifty pound bags of chips or granules, the average price per bag is $10-12 and you’ll need one to two pounds per square foot of soil.
There are many waterproofing companies that figure out the problem and do the work for you. Be certain the company gives you a written assessment of the problem and how it will be fixed. There should be a written estimate of cost, start date, completion date, and guarantee or warranty.
Insist on a written statement that there will be no work done without your consent, approval, and signature so there will be no unpleasant surprises when you get the bill. Ask around about contractors before hiring one; word of mouth generally carries the truth. Estimates can run from $2000 to $12,000, depending on the work to be done, so get more than one.
The cost of waterproofing a basement simply depends on the problem. Many can be done by the homeowner, some can’t. But the biggest source of water in basements is faulty or non-existent downspouts. And if you have a sump pump, be certain that it’s working. Look around. Make some notes. Now you have a place to start.