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Waterproofing a commercial property isn’t just about protecting one family—it’s about keeping multiple businesses and tenants safe. When you're working on a commercial building, making waterproofing a priority is key to avoiding big headaches like dry rot and mold.
So, where do you start? The foundation is a smart place. A good below-grade waterproofing system gives your building a strong base, keeping it in great shape for years to come. Not only will it save property owners from costly repairs, but it’ll also keep the space open for business—and making money.
We’re here to help you navigate the ins and outs of commercial waterproofing so your work holds up for the long haul.
Below-Grade Commercial Waterproofing – What is it?
While weatherproofing your entire commercial build is essential, it’s important to start with below-grade foundation waterproofing. This involves treating a surface or structure to prevent the passage of water under hydrostatic pressure.
Below-grade waterproofing is applied where the underground comes into contact with a structure. A few examples include:
- Horizontal concrete blocks
- Exterior walls
- Plaza decks
There's a range of moisture-proofing products that address any use case you could think of; we'll get to them in a bit.
The Benefits of Below-Grade Waterproofing
By using the right sealants and membranes, you can protect your commercial build from waterproofing failure, structural weakening, and human health hazards.
As you can imagine, without below-grade waterproofing, the foundation of a commercial or industrial structure is prone to moisture damage. This can impact its integrity to the point where the only option is restoring the building. Deterring water damage means reducing the amount needed to make any future repairs, are often incredibly costly for the owner.
Dry rot, mold, and the other negative effects of leaks can be difficult to see. The longer they exist, the more it'll cost to make repairs. Commercial waterproofing not only protects facilities from the immediate cost of fixing leaks; it also saves property owners money in the long run.
Preventative vs. Reactive Waterproofing
Commercial waterproofing can be either preventative or reactive.
Proactive measures usually happen during a build since waterproofing the foundation is a natural step in the construction process. During this phase, try to expand your understanding of the job site itself. A geotechnical report, for example, can help you understand the soil and the waterproofing solutions that will work best for the application.
Reactive measures are probably inevitable too; even the strongest below-grade waterproofing system can leak or wear down over time. Concrete-repair products and other restorative solutions can patch the problem and strengthen the area once again. Of course, the more proactive measures you set in place, the fewer "uh-oh" moments the owner will have later.
Waterproofing Methods Used in Construction
Because commercial waterproofing systems are so vital to safety and longevity, there are a slew of products and materials dedicated to below-grade use. (Some can be used both above and below ground.)
Positive vs. Negative/BlindSide Waterproofing
The use of positive vs. negative (blindside) waterproofing almost entirely depends on your crew's access.
Positive-side waterproofing is your go-to when you can easily access below-ground elements. Examples include vapor barriers, fluid-applied membranes, and even hot-applied bitumen systems. Don't forget to tack on some protection boards or insulation layers to keep that waterproofing layer safe when backfilling.
Negative-side waterproofing comes in handy when you can't reach the below-ground area. Negative-side goes on the interior surface after it's already been built, acting as a last line of defense. This method doesn't stop water from entering the substrate, but it can direct ingress to a drainage system.
Blindside waterproofing is also for tough-to-access areas, but you apply it before the structural slabs are in place. Rather than internal, it's location is between the ground and the underside of the slabs.
Vertical vs. Horizontal Waterproofing
As you've surely figured out, these strategies differ by the orientation of the surface you're protecting.
Vertical waterproofing create resistant barriers for wall envelopes below the ground. Fluid-applied membranes and other products seal off groundwater or rainwater that may otherwise seep in from the sides. Next time you're knee-deep in a below-grade project, don't overlook the vertical aspects!
Horizontal waterproofing is common in basements and tunnels. It's usually best to place it beneath the slab, either before or after you install the slab. Depending on your use case, horizontal waterproofing can be a standalone system or work in tandem with vertical waterproofing products.
The Types of Waterproofing Products
Understanding which products to use is just as important as the waterproofing process itself. Common options for commercial spaces include:
- Fluid-applied membranes – These hot- or cold-applied liquids are based on water, urethane, solvents, or cement. They're easy to spread with a roller, brush, or sprayer for a uniform finish, but drying takes some time.
- Sheet-applied membranes – These include modified bitumen, bentonite, elastomeric, and thermoplastic sheets that seal off water in every direction and prevent lateral migration. These products are self-adhering and can be pre- or post-applied, making them a versatile building envelope material.
- Coating – Primers can seal concrete and prepare a surface for application of asphalt or membranes. One newer product to watch is PUMA coating, a system rated for immersion and chemical exposure that's possible to cold-apply to finished flooring.
- Drainage – Composite mats and fabrics deflect water and relieve hydrostatic pressure in vertical and/or horizontal systems. When choosing one, strength and flow rate are important criteria, but don't forget to consider the sturdiness of your below-grade waterproofing membrane.
- Flashings – This reinforcing, self-adhered product – often made of rubberized asphalt – is installed inside walls. It collects water penetrating cracks in the exterior and directs it back outside.
Frequently Asked questions About Below-grade waterproofingHere are a few of the most frequently asked questions about below-grade waterproofing. What are the cost differences between various below-grade waterproofing methods and products?The cost of below-grade waterproofing methods can vary significantly based on the materials and techniques used. Fluid-applied membranes, for example, might have a lower initial cost compared to sheet-applied membranes, but they can also have higher application costs due to longer drying times and labor-intensive application processes. Sheet-applied membranes generally involve a higher upfront cost but offer long-term durability and ease of installation. Drainage systems and flashings add additional costs but are crucial for managing hydrostatic pressure and ensuring overall effectiveness. When evaluating costs, it's essential to consider both the initial investment and the potential savings from reduced maintenance and repair needs over time. How do environmental factors, such as soil type and climate, impact the choice of waterproofing methods?Environmental factors play a crucial role in determining the most suitable waterproofing methods. Soil type can influence the choice of waterproofing system; for instance, clay soils that retain water may require more robust drainage solutions to manage hydrostatic pressure effectively. Similarly, the local climate affects waterproofing choices: areas with high rainfall or freeze-thaw cycles might need more durable and flexible systems to withstand temperature fluctuations and prevent cracking. A thorough geotechnical report and an understanding of local climate conditions help tailor the waterproofing approach to ensure optimal performance and longevity. What are the long-term maintenance requirements for each type of below-grade waterproofing system?Long-term maintenance requirements vary by waterproofing system. Fluid-applied membranes may require periodic inspections to ensure that no damage has occurred and that the membrane remains intact. Sheet-applied membranes generally need less frequent maintenance but should be checked for any punctures or damage. Drainage systems must be regularly cleaned to prevent blockages that could compromise their effectiveness. Flashings and other components should be inspected for wear and tear, especially in areas where water might accumulate. Regular maintenance helps extend the life of the waterproofing system and prevent costly repairs due to neglected issues.
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Below-Grade Waterproofing Systems for Lasting Success
The sooner you account for moisture in a new or restorative commercial project, the higher your odds for success. By choosing waterproofing materials and methods that prevent rotting and mold, your build will keep structural and aesthetic value for years to come.
No matter the solution you need, there are plenty of below-grade waterproofing products available to get the job done. From blind-side and cold-applied membranes to hot rubberized asphalt and self-adhered flashings, what works best for your commercial build comes down to:
- The structure
- Its surroundings
- Any existing waterproofing system
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