Waterproofing Concrete: When It's Necessary and What to Use

Concrete and water have a complicated relationship. Concrete is porous by nature — it absorbs water, and water that gets into concrete causes problems ranging from surface staining to structural deterioration depending on where the water goes and what it affects along the way.

A standard sealer handles surface moisture for most applications. But there are situations where a sealer isn't enough — where water management requires a dedicated waterproofing system designed to prevent water penetration entirely rather than just slow it down. Knowing the difference between those situations and understanding what the options are can save a significant amount of money and headache.

When a Sealer Is Enough

Before getting into waterproofing, it's worth being clear about what standard sealing accomplishes and when it's the right tool for the job.

A penetrating sealer applied to a concrete surface reduces water absorption by filling the pores near the surface with a water-repellent compound. For most horizontal outdoor surfaces — patios, driveways, pool decks, walkways — a quality penetrating sealer provides adequate moisture protection. Water beads on the surface, doesn't penetrate deeply, and evaporates without causing damage.

Topical sealers add a film-forming layer that further reduces moisture penetration and protects the surface from staining and wear. For most residential concrete surfaces in Las Vegas, a good sealer maintained on a regular schedule is all the moisture protection the surface needs.

The situations where sealing isn't enough are specific and worth knowing.

When Waterproofing Is Necessary

Elevated Decks Over Occupied Space

This is the most common situation where a full waterproofing system is not optional. An elevated deck — a second-floor balcony, a rooftop terrace, a deck built over a garage or living space — has an occupied area below it. Any water that penetrates the deck surface will find its way into that space below.

A sealer reduces surface water absorption but it doesn't create a fully waterproof barrier. Water that gets through a cracked sealer, through control joints, or through substrate cracks in an elevated deck will drip into the space below. Over time, that moisture causes structural damage to the framing, ceiling damage to the space below, and mold issues that are expensive and disruptive to address.

Elevated decks over occupied space require a waterproofing membrane system — a continuous, fully bonded barrier that prevents water from reaching the structural substrate regardless of what happens to the surface coating above it.

Below-Grade Applications

Concrete walls and floors that are below grade — basement walls, retaining walls, planter walls — are in contact with soil that holds moisture. Ground water pressure pushes against these surfaces and water will find any path through the concrete it can. Standard sealers applied to the surface don't perform well against positive water pressure from the exterior face of a below-grade wall.

Waterproofing below-grade concrete requires systems specifically designed for negative-side or positive-side waterproofing depending on where access is available and which direction the water pressure is coming from.

Planter Boxes and Planter Walls

Planter boxes built from concrete or with concrete bases are a specific waterproofing application that's relevant in Las Vegas where outdoor planters are common in residential and commercial landscapes. The combination of irrigation water and soil chemistry is corrosive to unsealed concrete over time, and water that migrates through a planter wall or base can damage adjacent structures.

A waterproofing system applied to the interior surfaces of a planter box protects both the concrete and any adjacent structure from water migration.

Concrete in Contact With Constant Moisture

Any concrete surface that's in regular contact with water — the interior of a water feature, a fountain basin, a koi pond — needs waterproofing rather than just sealing. The constant hydrostatic pressure and the chemistry of standing water overwhelm standard sealers quickly.

Understanding Waterproofing Systems

Waterproofing systems are more involved than applying a sealer. They typically involve multiple components that work together to create a continuous, redundant barrier. Here are the main system types.

Sheet Membrane Systems

Sheet membrane waterproofing involves bonding a prefabricated membrane — typically a modified bitumen or synthetic rubber sheet product — directly to the concrete substrate. The membrane creates a continuous barrier that bridges cracks and joints when properly installed.

Sheet membranes are among the most reliable waterproofing options for elevated decks. The material itself provides a high level of waterproofing performance independent of the substrate condition, and the physical thickness of the membrane gives it resilience against minor substrate movement.

Installation requires careful attention to detailing at transitions — edges, drains, penetrations, and corners. These transition points are where most waterproofing failures originate regardless of the system type. A sheet membrane that's perfectly installed on the field area but poorly detailed at a drain penetration will fail at the drain.

Liquid-Applied Membrane Systems

Liquid-applied membranes are applied as a liquid coating that cures to form a seamless, fully adhered waterproof film. They're applied by roller, brush, or spray and conform to the substrate surface without the seams that sheet membranes have.

The seamless nature of liquid-applied systems is an advantage — there are no seams to fail. The limitation is that the waterproofing performance depends on achieving consistent thickness across the entire surface during application. Thin spots compromise the barrier. Most liquid-applied systems are applied in multiple coats with reinforcing fabric embedded at transitions and in crack-prone areas to improve performance at those locations.

Crystalline Waterproofing

Crystalline waterproofing works differently from membrane systems. Rather than creating a barrier on top of the concrete, crystalline products penetrate into the concrete and react with water and cement particles to form crystals that fill the capillary pores and microcracks within the concrete matrix itself.

The result is that the concrete itself becomes the waterproofing barrier rather than a separate membrane applied to it. Crystalline waterproofing is particularly well suited to below-grade applications and situations where surface-applied membranes are impractical. It's also self-sealing — if new cracks form within the treated zone, the crystalline reaction is reactivated by moisture contact and seals them.

The limitation is that crystalline systems are not appropriate for situations with significant hydrostatic pressure or for joints and cracks that are actively moving. They work best in concrete that's structurally stable and where the waterproofing challenge is capillary moisture rather than pressure-driven water penetration.

Traffic-Bearing Waterproofing Systems

For elevated decks and balconies that need to support foot traffic or vehicle traffic, a traffic-bearing waterproofing system combines the waterproofing membrane with a wear surface that's durable enough to handle the intended use.

These systems typically involve a base waterproofing membrane, one or more reinforcing layers, and a top coat formulated for the specific traffic type. The system is designed so that the wear surface can be replaced when it shows wear without disrupting the waterproofing membrane below — which means the long-term maintenance cost is lower than a system where the wear surface and waterproofing are the same layer.

See our waterproofing system products here.

Drainage Is Part of Waterproofing

No waterproofing system works well without adequate drainage. Water that ponds on a waterproofed surface puts sustained pressure on the system, finds any weakness in the membrane, and eventually forces its way through. Proper slope to drain and functioning drain systems are essential components of any waterproofing installation.

For elevated decks, the drain assembly itself is a critical detail. The drain needs to be integrated with the waterproofing membrane in a way that prevents water from bypassing the membrane at the drain penetration. This is one of the most common failure points in deck waterproofing and it's worth paying close attention to during installation.

See our deck drain products here.

Las Vegas Specific Considerations

Las Vegas gets significantly less annual rainfall than most US cities, which might suggest waterproofing is less of a concern here. In practice, the opposite is often true for certain applications.

When it does rain in Las Vegas, it frequently rains hard and fast. Monsoon-pattern storms can drop significant rainfall in a short period. A surface that can handle light, slow rain may be overwhelmed by the volume and intensity of a Las Vegas summer storm. Waterproofing systems that are designed for proper drainage capacity handle these events without stress.

The intense UV in Las Vegas also affects waterproofing membranes. UV-stable formulations and UV-protective top coats are important for any exposed membrane component. A membrane that degrades from UV exposure loses its effectiveness regardless of how well it was installed.

Temperature cycling affects joint sealants and transitions within waterproofing systems. The expansion and contraction of concrete in Las Vegas temperature swings — hot days and cooler nights even in summer — puts stress on these details. Using flexible, temperature-rated sealants at joints and transitions is important for long-term performance.

Getting Waterproofing Right

Waterproofing is one of those applications where the cost of getting it wrong significantly exceeds the cost of doing it correctly the first time. Water damage to the space below an elevated deck, structural deterioration of a below-grade wall, or persistent moisture damage to an adjacent structure from a failed planter — these are expensive problems to fix after the fact.

If you're assessing a waterproofing need and aren't sure which system is appropriate, come talk to us. We carry a range of waterproofing products and we can help you understand which approach makes sense for your specific application.

South Las Vegas: 4125 Wagon Trail Ave, Las Vegas, NV 89118
North Las Vegas: 4601 E Cheyenne Ave Ste 107, Las Vegas, NV 89115
Phone: (702) 749-6318

Or reach out through our contact page and we'll get back to you.