Waterproofing vs damp proofing

Posted by Luc Gerber on Wed, Feb 04, 2015 @ 02:49 PM

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Damp-proofing and waterproofing are two terms in the basement waterproofing industry that are often use interchangeably; however, it is important to distinguish between waterproofing and damp-proofing as they are not one and the same. They are correctly defined as follows:

Waterproofing: Treatment of the surface or structure to prevent the passage of water through the building envelope under hydrostatic pressures. Waterproofing provides a full and continuous barrier to water penetration.

Damp-proofing: Treatment of a surface or installation of a technology to resist the passage of moisture caused by differences in moisture content, vapour pressure and temperature across the basement envelope to prevent accumulation of water against the outer surfaces of the envelope (walls and floor slab).

The distinction between waterproofing and damp-proofing is very important because these treatments provide certain barriers to basement water infiltration accomplished via distinctly different methods.



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Waterproofing and Damp Proofing in detail

Foundation Waterproofing

Foundation waterproofing involves the application of a waterproof coating onto the exterior of a foundation, the purpose of which is to provide a barrier through which water cannot penetrate. The three most common waterproofing materials in current use are:

  1. Tar;
  2. Elastomeric rubber coatings; and
  3. Blue-skin®.

While tar is not as effective as the other two materials in keeping water from penetrating basement walls, it is the product which is the standard used to waterproof foundation walls in new construction applications. The following image shows a foundation wall that is waterproofed with an elastomeric rubber coating.

Waterproof Foundation Wall 
Waterproof coating on foundation wall
 An elastomeric coating is thick and hand applied, and stretches


Foundation Damp-proofing

Foundation damp-proofing involves the installation of a plastic foundation wrap, or membrane / air-gap membrane, installed onto a waterproofed foundation wall. A proper membrane is configured to facilitate the flow of water, in proximity to a foundation wall, to the weeping tile. Also, the membrane provides a barrier to keep wet soils from being in constant contact with the exterior foundation wall surface. Below is an image of installed air-gap membrane / foundation wrap.

 Damp proof membrane on foundation
Damp proofing membrane installed on foundation
 An air-gap membrane keeps foundation walls from constant contact with wet soil


It is worthwhile noting that foundation coatings which are not elastic may also be considered as damp proof coatings; in fact, such sprayed-on coatings are the norm for newly constructed foundations in Ontario.

It is a common misconception that foundation wrap will waterproof a basement wall; this is not the case as the membrane in not impervious to water at all of its edges. Only foundation coatings will waterproof a wall.


Topics: basement waterproofing, foundation waterproofing, dampproofing foundations