Keeping water out of a basement is a multi-approach process. Water must be kept from entering the basement from the outside and the interior parts must also be protected. New basements have the challenge of being untried for water exposure. The best way to waterproof a new basement is to employ protection from multiple sources.

Exterior Options

Part of keeping a new basement dry begins before construction is complete. Since basements are lower than the surrounding areas, proper drainage and ground grading are essential for keeping basements dry. A home with a basement should have the ground slope away from the house. The ground should fall at least 6 inches within 4 feet of the house. Better drainage occurs when the grading is even steeper. It can also be useful to improve the natural drainage of the ground by mixing in some rocks and sand around the lowest part of the yard to encourage drainage. Working gutters and downspouts are also essential for keeping any basement dry. Gutters should be large enough to prevent water from seeping over the edges of the drain. The drain pipes should also drain several feet away from the walls of the house. For extremely poor drainage, drain pipes can be extended out several feet beyond the house and drained into a rock-filled barrel with holes to encourage drainage away from the home.

Interior Options

Sometimes, even with excellent drainage and gutters, moisture still seeps into the basement walls and floor. A water sealant can be painted on the walls and floor of the basement to prevent moisture from seeping in. Cracks should be filled with a putty designed to keep water out. Any leaks inside the basement should be repaired immediately to prevent further damage to the basement. A cement mixture designed to waterproof can also be used to fill any large cracks. Do not seal any cracks until the cause of leakage is known. Patching a larger issue can create many more problems down the line.

Installation Tips

A new basement will not show evidence of problems for a while. It is important to make sure that the basement was built properly before anything is placed in the basement. Any basement will benefit from the application of water sealant paint. Apply like regular paint and allow to dry for at least 24 hours before use. You should measure the grading on the house to ensure that water will drain away from the house rather than into the basement. Install gutter drains along the roof to prevent water from dripping off the roof and seeping into the basement.

Source:

New York Times: Basement Water Removal

This Old House: Basement Waterproofing