Vancouver Humidity Control Ltd. and Rising Damp

Rising damp in this foundation wall is causing excessive moisture inside the building (picture courtesy VHC)

Mold has become a major concern for occupants, health officials, builders and architects. Rising damp, the wicking of water through concrete and its evaporation inside the building, can be a major contributor to moisture and humidity, prime conditions for mold.

Vancouver, Canada, with over 60" of rain per year, has a history of moisture-related problems in buildings, with recent leaky condo damages exceeding $2 billion.

Kevin North, President of Vancouver Humidity Control Ltd., Surrey, BC, has been involved in the remediation of buildings suffering from excessive moisture for over ten years. Prior to this, he spent 16 years supervising the installation of site services in residential subdivisions, allowing him to obtain first hand experience on the implications of site drainage on building moisture.

"When we excavate down to existing drains we often find water puddling beneath the invert of the drain pipe", said Kevin. "These pipes are typically high and dry but the water is trapped in the space below the invert of the pipe and above the bottom of the excavation. With impervious soil, such as clay, water puddles will form up to the height where the drain tile starts to function."

"The zone between the bottom of the excavation and the invert of the drain pipe is akin to the zone between the low and high tide mark on a beach. Would you even think about putting a footing in that zone? If you do, then expect it to get wet. Drain tiles relieve hydrostatic pressure; they do not stop the structure from getting soaked. This is a huge misconception."
 

Notice the mold growing on the wood studs and concrete wall behind (picture courtesy VHC)

"As concrete has the ability to wick water from its surroundings", continued Kevin, "the concrete footing will transfer ground moisture to the inside of the building. Furthermore, interior heat increases the rate of evaporation, leading to higher levels of moisture either in the crawl space, or behind the walls of the finished basement."

"I often explain to homeowners that wicking is like children's pants being wet past the knees, when the puddles they play in are only 2" deep", said Kevin. "Concrete transfers water using the same mechanism."
 

Severe rising damp is occurring in this slab, footing and foundation wall (picture courtesy VHC)

These problems can be corrected by removing the water puddles from the foundation concrete through proper drainage. "The drain tile must be replaced away from and below the concrete footing. Expensive repairs are eliminated when the building is constructed correctly in the first place. Sadly, the building code does not deal with water ponding and rising damp in concrete, at least not yet," said Kevin.
 

Severe mold growth can be seen on the wood studs as a result of rising damp in this crawl space (picture courtesy VHC)

"The waterproofing industry does an excellent job in protecting the concrete foundation wall from moisture. But the industry fails at the most important level, the footing, where all the water accumulates", he lamented.

Pictures courtesy of Kevin North, Vancouver Humidity Control Ltd., Surrey, BC, (604) 507-0269