What is Waterproofing and How is it Different than Damp Proofing?

Posted on October 22, 2015


When you’re having moisture problems, you may hear the terms waterproofing and damp proofing tossed around. But to the average person, what’s the difference – they both limit the transfer of water through materials, right? As it turns out, there’s a lot of difference – especially if you’re worried about basement moisture problems. Let’s take a quick look at what waterproofing and damp proofing are and how they’re different:

What is Waterproofing?

Waterproofing is keeping all water from crossing a material, including soil moisture, water vapor and liquid water that is under hydrostatic pressure. If you live in a damp climate that tends to have problems with basement flooding, this is an important difference to note. The International Residential Code (IRC) requires waterproofing from the top of the footing to the finished grade in areas that have high water tables or where there are problems with severe soil water conditions. As a porous surface, concrete can quickly soak up water using capillary action between the aggregate if left untreated. Waterproofing compounds can keep cracks covered as they develop, because it’s a flexible material that retains its initial elasticity and is applied more thickly, typically up to 40 mils, four times the thickness of damp proofing compounds, to the foundation. By sealing the concrete with a waterproofing substance, you’re providing additional protection to the structure.

What is Damp Proofing?

By comparison, damp proofing only controls water vapor from soil moisture. It won’t stop the influx of liquid water, so don’t damp proof a foundation thinking that will be sufficient if you have high water tables or severe soil water conditions. In other areas, damp proofing can be used in the same area that waterproofing would otherwise be used – from the finished grade to the top of the footing. It typically consists of a sealant applied to the exterior of the foundation walls to control the movement of soil water vapor into the structure. At a mere 10 mils thick, it doesn’t have the ability to seal large cracks, doesn’t deal well in places where ties protrude away from the surface and similar problematic areas. It can also be easily damaged when backfill is put into place by a careless operator, so if you decide to use it in place of waterproofing, make sure you are very careful around it. Proper foundation drainage and design elements that reduce hydrostatic pressure will help keep your damp proofed foundation working effectively.

What’s the Difference?

As you can see by the definitions, waterproofing is essentially damp proofing plus a lot more performance. Overall, waterproofing provides a higher quality seal against water in your foundation walls and keeps the structure as a whole more comfortable to occupy. If you live in a dry climate, have strong control over the quality of work done in preparation and with earthmoving equipment to backfill the foundation or have the ability to put drainage features in place to control hydrostatic water pressure, damp proofing is a cost-effective way to keep areas below grade comfortable. If you require better performance out of your sealant, live in areas with severe soil water conditions or high water tables, are willing to spend a little more to get a higher quality construction, waterproofing is an excellent choice.

Now that you know the differences between waterproofing and damp proofing, you can make the best choice for your next project that will leave you comfortable and with dry feet. If you still have questions or need help figuring out the best possible way to make your project go well, please feel free to contact the experts at BN Products. We’re always happy to help make sure your project is a success.