Dampproofing is a water-resistant coating designed to shed water and resist soil moisture. It's the default for any poured concrete wall below grade. But on sites with slow-draining soils or high water tables, or where site drainage is unreliable, a waterproofing system designed to resist water under hydrostatic pressure will be needed.
Login or Register to download the PDF version of this guide. (193.76 kB)
Dampproofing
A simple dampproof coating is sufficient where positive drainage is reliable, the seasonal water table never rises above the footing, or the basement is not living space.
Dampproofing Concrete Block Basements
Spray-applied waterproofing and some waterproofing membranes can be applied directly to concrete block. However, dampproofing should be applied over parging.
Parging Concrete Block
Before parging walls, brush off any dirt and dampen wall with a water spray (do not soak).
To parge walls, trowel on two coats of Type M or S mortar. Each coat should be at least 1/4 in. thick, for a total minimum thickness of 1/2 in. Roughen the first coat with a brush when the wall is partially dry to ensure good bonding.
Allow the first coat to harden for 24 hours before applying the second coat. Cure the topcoat for 48 hours before applying dampproofing.
Form the parging into a cove where the wall meets the footing to direct water away from the joint (below).
Figure: Parging for Concrete Block Foundation
Parging should be applied to block foundations before applying a dampproof coating. At the bottom of the wall, flare the parging into a cove to shed water from the footing/wall joint.
