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What are the Best Methods for Building a Waterproof Cellar?

Dana DeCecco
Dana DeCecco

The best methods for building a waterproof cellar begin at the foundation stage of the construction process. Typical designs include a waterproof coating. A french drain is a necessary component of a waterproofing system. Diverting excess ground and roof drainage is critical to ensure a waterproof cellar.

Once the footer has been poured and the foundation walls set in place, the waterproofing process begins. The construction site will determine the type of waterproofing system that can be installed. A relatively flat building site with a high water table, for example, will require a mechanical sump pump to displace the water build up.

Cellars can use drainage systems with sump pumps to remove excess water.
Cellars can use drainage systems with sump pumps to remove excess water.

Foundation walls are typically constructed of concrete block or poured concrete. In either case, a waterproof coating must be applied to the exterior surface. In the case of concrete block, the exterior wall surface below the finished grade should be coated with a cement parge. This thin layer of cement is applied like plaster over the concrete blocks.

A gravel base may be used under a cellar floor to help with waterproofing.
A gravel base may be used under a cellar floor to help with waterproofing.

The next step to ensure a waterproof cellar is to coat the foundation with asphalt foundation. Two coats are recommended, and ample drying time should be allowed between coats. Many other foundation coatings, including latex-based products, are also available. Rubber or plastic membranes can be applied if the budget permits.

A french drain is composed of perforated pipe, membrane, and gravel. This feature is absolutely necessary to ensure a waterproof cellar. A drain of this type should be installed at the footer level. Water around the foundation wall area will be captured by the french drain and diverted.

The french drain system should be installed around the perimeter of the foundation walls. The perforated pipe should run dead level or pitched slightly toward the run-off area. If the construction site is on a grade, the run-off should be diverted downhill. If the construction site is flat, the run-off will need to be diverted to a sump pump, which will pump water to an area that will not drain back toward foundation walls.

Proper finish grading of the site will help maintain a waterproof cellar. The finished grade should be sloped away from the foundation walls. This will ensure that excess surface water drains away from the structure.

Before pouring the concrete basement floor, a waterproof vapor barrier should be applied over a gravel base. The vapor barrier can be a heavy grade of plastic. This will prevent water vapor from penetrating the concrete basement floor.

The final step to ensure a waterproof cellar is to divert all roof water away from the structure. Gutters and downspouts that collect water run-off from the roof should empty into a non-perforated pipe. This water should them be diverted to an area that does not drain back toward the structure.

The best methods for ensuring a waterproof cellar are done on the exterior of the structure. Such methods help to remove water from existing wet basements and other interior areas of the structure. The best method for ensuring a waterproof cellar is to stop the water before it enters the structure.

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    • Cellars can use drainage systems with sump pumps to remove excess water.
      By: oocoskun
      Cellars can use drainage systems with sump pumps to remove excess water.
    • A gravel base may be used under a cellar floor to help with waterproofing.
      By: nito
      A gravel base may be used under a cellar floor to help with waterproofing.