Damp proofing and waterproofing are two different strategies for protecting the building envelope. While they both play an important role in watertightness, they slightly differ in their purpose. Damp proofing is intended to keep out soil moisture out of exterior walls, while waterproofing keeps out both moisture (or water vapor) and liquid water out of the building.6 Both strategies impede mold growth.
Tar No More!
Historically, a common damp proofing strategy for masonry walls has been tar. Tar is a dark brown or black bituminous usually odorous viscous liquid obtained by destructive distillation of organic material (such as wood, coal, or peat).9 Over time, tar does not prove durable due to its brittleness.6 Coal tar contains harmful VOCs and known carcinogens 7 and it is no longer recommended as a construction material,1 with many states even banning its use.8
Areas of concern with asphalt
A more common product for damp proofing and waterproofing is bitumen, also known as asphalt. One area of concern for asphalt-based materials is its production. This process releases hazardous chemicals such as hydrogen sulfide, lead, and copper.2 Hydrogen sulfide exposure may cause irritation to the eyes and respiratory system.5 Exposure to lead and copper may cause health problems ranging from stomach distress to brain damage. 11
Another area of concern for asphalt-based materials is installation. Installation crews are inevitably exposed to bituminous fumes, which are identified as occupational carcinogens.2 Short-term health effects include throat and eye irritation, skin rash, and reduced appetite.3
Who is most at risk?
Aside from installation crews, fenceline communities are most at risk. Also known as frontline communities, these are neighborhoods located immediately adjacent to raw material extraction processing locations. These are very often low-income communities. Communities of color also tend to be the most impacted. 2
Healthy Building Network ranks bentonite sheet waterproofing membranes as a healthier alternative. After installation, these membranes will not off-gas or release harmful chemicals during their lifetime. However, the production and installation phases are still cautionary because they expose miners to bentonite dust. Significant levels of silica, a carcinogen, are found in this dust.
While health concerns exist, bentonite sheet waterproofing is still the preferred product compared to the rest of the options available in the industry.
✓ Search for materials that are not asphalt-based.
✓ Specify bentonite sheet membranes when seeking a waterproofing application.
✓ Choose materials that are completely inert (chemically inactive, stable) such as sheet/membrane waterproofing systems.
✓ Recommend parging below-grade walls before application of damp proofing and waterproofing materials4
✓ Select products that contain little to no VOCs
✓ Eliminate solvent-based products
✓ Avoid polyurethane waterproofing
Visit these sources for more information.