Dampproofing vs. Waterproofing: Know the Difference

Waterproofing typically only makes up 1.8% of a building’s construction costs. However, after completion, roughly 83% of building defect complaints relate to the waterproofing –- or lack thereof. 

Investing in comprehensive waterproofing measures during construction is critical for protecting commercial property over the long haul. However, in construction, there is the eternal debate: dampproofing vs. waterproofing. Both can prevent water infiltration. However, there are differences when it comes to cost, movement, and hydrostatic pressure (just to name a few). Which one is your goal, and how do you achieve it successfully?

The good news: By keeping dampproofing and waterproofing materials and techniques in your arsenal, you’ll be ready to secure any commercial building envelope. Let’s prepare you to purchase the best materials for the building environment and meet your water protection needs. 

Commercial Waterproofing: What Is It?

The American Concrete Institute (ACI 515.1) defines waterproofing as “treating a surface or structure to resist water infiltration under hydrostatic pressure.” The intent, therefore, is to seal water out totally, reducing the structure’s risk of weakening due to rotting and mold growth. 

Waterproofing is necessary in specific scenarios, including:

• Below-grade structures (particularly those that are going to be exposed to more water than the moisture in the soil)
• Areas with high water tables, and regions prone to heavy rain or flooding
• Commercial, industrial, or heavy-duty applications

There are three types of waterproofing systems. The main difference in each is where you’re able to apply it:  

• Positive-side: This system goes on the external surface of the structure. This method is considered the most effective, as it prevents water from entering the structure in the first place. Common examples include waterproofing membranes applied to foundation walls or roofs before backfilling or installing the final finish.
  
  
• Negative-side: This technique is applied to internal surfaces, such as basement walls or floors. It's typically used when positive-side waterproofing isn’t feasible or as an additional layer of protection. Negative-side waterproofing is more challenging to install and maintain because you have to apply it to a completed structure.
  
  
• Blindside: Save this specialized technique for when access to both the positive and negative sides of the structure is minimal or impossible. It involves applying a waterproofing membrane to the foundation or underground structure before casting the concrete or backfilling. This method is common in deep excavations, tunnels, or underground parking garages.

There are different product formats as well, including: 

• Sheet membranes: These pre-formed layers are common in roofing and foundational waterproofing. They consist of rubberized asphalt or a polymeric compound that sticks to the substrate.
  
  
• Cold liquid: These are applied as a fluid at ambient temperature. They cure to form a watertight membrane for roofs, decks, and balconies.
  
  
• Hot-applied: These products require heat to cure. Usually asphalt-based, they provide a thick, durable barrier. Use them in areas where you expect heavy water exposure.
  
  
• Sodium bentonite: These clay-based weatherproofing materials swell upon contact with water. They’re effective on below-grade foundations, creating an impermeable barrier.
  
  
• Cementitious products: Cement, sand, and additives combine here create a new, surface-protecting material. Use them in areas where moisture is inevitable, i.e. water tanks and basements. This use case is typically negative-side or for crystalline waterproofing.

High-quality waterproofing membranes will far outperform all dampproofing materials, in both performance and long-term durability. So, despite the higher up-front cost, it’s a stronger investment.

Commercial Dampproofing: What Is It?

Dampproofing is a structural treatment to resist water infiltration, and mostly focuses on the exterior surface of a building. It does NOT keep water out – it’s more about minimizing moisture. Dampproofing materials mainly stop water from wicking through wet or damp concrete. 

Dampproofing a lesser-quality solution, and sometimes enters a commercial project as a result of “value engineering.” You might see it in a private suburb where the real estate agent has no desire to spend on full waterproofing, but not large-scale commercial work.

Dampproofing compounds are generally asphalt-based, water-repellent, and applied in liquid form. Application methods include brushing, rolling, or spraying to any foundation or basement wall surfaces that have direct contact with the earth. Dampproofing involves materials like tar-based coatings and cementitious coatings (which are applied at up to 10 mils of depth and cure quickly).

These products are for use in areas with low moisture levels and less risk of water pressure buildup. With those intentions, it makes sense that contractors rely on dampproofing more often for residential construction projects, where the walls are above-grade and lighter-duty. 

Dampproofing vs. Waterproofing: Making the Right Choice 

Evaluating the site before construction typically includes gathering information on the structure’s exposure to moving water and expected weather fluctuations over time. With those in mind, it may be an easy enough decision between waterproofing and dampproofing. However, considering both methods and the relevant code requirements is still a good idea before purchasing commercial waterproofing systems. 

*As you might expect, exact cost will vary depending on the installation location (interior vs. exterior) and your choice of material. 

Pro Tip: While this includes installation by experienced weatherproofers, the total bill could include up to an additional $200 per hour to account for experience and project scope. 

[Checklist] Waterproofing vs. Dampproofing Questions that Need Answered 

With the following factors all outlined clearly, you’ll have a better sense of what the project needs in terms of dampproofing and waterproofing. 

Is there a below-grade element to the structure?
What are the relevant local building codes?
What environmental conditions are we working with?
What is the future intended use of the structure?
What is the budget?

While the initial budget is always a top priority, now is also the time to weigh the potential future maintenance costs resulting from choosing to save money initially.

Take this example: Say you’re constructing a single-story, above-grade building. You can treat the area that transitions from the slab edge to the footing with dampproofing material to save your client costs, since there’s no below-grade finished, occupied space like a basement. If your external ground level is lower than the inside floor level, then your risk of pressurized water ingress is lower and dampproofing would make sense.

Planning Ahead for Dampproofing & Waterproofing

Water damage is one of the most costly threats facing building owners and property managers. Even relatively minor leaks or moisture intrusion can lead to expensive structural problems, mold growth, deterioration, and hazardous living conditions if left unchecked. 

The main point to answer the question of waterproofing vs. dampproofing relates to the likelihood of hydrostatic pressure. From there, it’s a matter of initial cost, mobility, crack coverage, and the expected temperature fluctuations. Knowing what priorities are key to your project will streamline this decision process. 

Consult with professionals to make informed decisions, or, if you’re not ready for that step, keep learning!

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