6 Best Waterproofing Sprays for Apartment Exteriors That Prevent Costly Damage
Prevent costly water damage to your apartment exterior. We review the 6 best waterproofing sprays for reliable, long-term protection against the elements.
You hear the drip long before you see the damage. That tiny, persistent sound is the start of a much bigger problem—one that can lead to rotted wood, crumbling drywall, and a mold issue you can’t ignore. In a compact living space like an apartment, even a small water intrusion can cause catastrophic, expensive damage. The good news is that a little preventative maintenance with the right waterproofing spray can save you thousands in repairs and countless headaches down the road.
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Why Your Apartment Exterior Needs Waterproofing
Water is relentless. It will find any crack, any unsealed joint, any porous surface to work its way into your home. For apartment dwellers, common culprits are often overlooked: the seam where your balcony meets the building, the aging caulk around your window frames, or the porous brick of an exterior wall.
These small entry points are invitations for big trouble. A slow leak can saturate insulation, rot structural supports, and create the perfect dark, damp environment for mold to thrive. By the time you see a water stain on your interior ceiling or wall, the damage behind it is often far more extensive than you imagine.
Think of exterior waterproofing not as a repair, but as insurance. You’re not just fixing a leak; you’re creating a barrier that protects your home’s structure and your peace of mind. A few dollars spent on a can of sealant today can prevent a multi-thousand-dollar repair bill tomorrow. It’s one of the most cost-effective upgrades you can make to protect your space.
Rust-Oleum LeakSeal for Cracks and Joints
Seal leaks instantly with Rust-Oleum LeakSeal Flexible Rubber Coating Spray. This oil-based formula creates a protective barrier on various surfaces, preventing water penetration and filling small gaps. It dries to touch in 30 minutes and can be top-coated for a finished look.
When you have a specific, targeted problem, you need a specific, targeted solution. Rust-Oleum LeakSeal is that solution. This isn’t for waterproofing an entire wall; it’s for zeroing in on the small cracks and gaps where water first gets in.
Think of it as a flexible, rubberized bandage in a can. Its best use is for sealing the joints around window and door frames, vents, and ductwork. The spray builds a coatable layer that remains pliable, so it won’t crack as the building naturally expands and contracts with temperature changes. This flexibility is its greatest strength.
The application is straightforward: clean the area, spray a thin coat, and let it dry before adding another. Multiple thin coats create a much stronger and more durable seal than one thick, messy layer. Once cured, you can even paint over it to match your exterior, making the repair virtually invisible. It’s the perfect tool for precise, preventative sealing.
Gorilla Patch & Seal for All-Weather Use
Sometimes, you can’t wait for a sunny day to fix a leak. Gorilla Patch & Seal is the emergency tool you need for exactly those situations. Its standout feature is its ability to be applied to wet surfaces, instantly stopping a leak in its tracks.
This spray is an absolute beast when it comes to adhesion and durability. It creates a thick, rubberized coating that is self-leveling and resistant to extreme temperatures, making it ideal for everything from a leaking gutter joint above your patio to a crack in a skylight. It sticks to almost anything—metal, concrete, wood, and even PVC.
The tradeoff for this incredible strength is its appearance. It goes on thick and isn’t as subtle as other options, so it’s more of a functional fix than an aesthetic one. But when you have water actively coming in, function is all that matters. This is the can you grab for an immediate, no-nonsense repair.
Flex Seal Spray: The Versatile Rubber Coating
Stop leaks instantly with this transparent, waterproof rubber sealant. It seeps into cracks, dries to a flexible, watertight coating, and protects surfaces from corrosion. Ideal for a wide range of repairs on various materials.
You’ve seen the commercials, and for general-purpose waterproofing, Flex Seal lives up to much of the hype. It’s a fantastic all-rounder that works on a huge variety of surfaces, making it a great product to keep on hand for unexpected issues. It seeps into small openings and dries into a watertight, flexible barrier.
This versatility is its key selling point. Use it to coat the bottom of metal patio furniture to prevent rust stains on your concrete, seal a small crack in a plastic planter, or add a waterproof layer to the underside of a wooden window box. It creates a clean, rubbery finish that can handle minor flexing and movement without failing.
However, don’t mistake it for a structural gap filler. For larger cracks or holes, you’ll need a different solution or have to build up many, many coats of Flex Seal. For broad surface protection and sealing minor imperfections on common materials, it’s a reliable and easy-to-use choice.
Thompson’s WaterSeal for Patios and Decks
Some surfaces don’t have a single crack to fill but are porous by nature. We’re talking about concrete patios, wooden deck tiles, and unglazed brick pavers. For these, you don’t need a gap filler; you need a penetrating sealer like Thompson’s WaterSeal.
Unlike rubberized coatings that sit on top of a surface, Thompson’s soaks into the material. It fills the microscopic pores in wood and concrete, preventing water from being absorbed in the first place. This is crucial for preventing freeze-thaw cycles in colder climates, where absorbed water freezes, expands, and causes concrete to spall and wood to splinter.
Applying it is more like staining than painting, often done with a pump sprayer or roller for even coverage. The biggest consideration is that it’s a maintenance product, not a one-and-done fix. Depending on your climate and the amount of foot traffic, you’ll likely need to reapply it every one to three years to maintain the protective barrier.
Drylok Extreme for Brick and Masonry Walls
Instantly stop active water leaks with DRYLOK Fast Plug Hydraulic Cement. This gray powder mixes with water to set in 3-5 minutes, effectively patching masonry cracks and anchoring metal. It withstands significant hydrostatic pressure and requires no topcoat.
If you have a persistent dampness issue on a brick or concrete block wall, you need to bring out the heavy artillery. Drylok Extreme is a specialized waterproof paint designed to stop water from passing through masonry, even under pressure. It’s a serious solution for serious water problems.
Drylok isn’t a simple spray-on coating; it’s a thick, paint-like substance that you apply with a brush or roller. It works by penetrating the surface pores and bonding with the masonry to create a truly impenetrable barrier. This is the product to use on a ground-floor apartment’s exterior foundation wall or a retaining wall that stays damp after it rains.
The main tradeoff is that it completely changes the look of the surface. It covers the natural brick or concrete with an opaque, paint-like finish. However, it’s tintable to different colors, and when you’re facing potential water damage inside your apartment, sacrificing the original look of a problematic wall is a small price to pay for a dry, healthy living space.
Liquid Rubber Sealant for Foundation Seams
Waterproof and protect surfaces like roofs, planters, and foundations with this flexible, UV-stable sealant. The water-based formula is environmentally friendly and easy to apply indoors or outdoors.
The joint where your apartment’s concrete slab or foundation wall meets the ground is one of the most vulnerable spots for water intrusion. For sealing this critical seam, you need a product that offers extreme durability and flexibility, and that’s where Liquid Rubber comes in.
This is a professional-grade sealant that creates a thick, seamless, and highly flexible waterproof membrane. It’s designed for the toughest jobs, like sealing foundation cracks or coating the entire base of a retaining wall. When applied correctly, it forms a powerful barrier that can stretch and move with the building, ensuring the seal never breaks.
While it’s available in a spray can for smaller jobs, it’s often applied with a brush or roller for larger areas. It requires a thoroughly clean and dry surface for proper adhesion, so prep work is key. This is not for a quick cosmetic fix; it’s for creating a long-term, industrial-strength seal on the most critical parts of your exterior.
How to Properly Apply Exterior Sealing Sprays
The best waterproofing spray in the world will fail if it’s not applied correctly. The secret to a lasting, watertight seal isn’t in the can—it’s in the preparation. Rushing the job will only guarantee you’ll be doing it again next season.
First, clean the surface relentlessly. Scrape away any loose paint, scrub off dirt and mildew with a stiff brush and cleaner, and rinse it thoroughly. Most importantly, let it dry completely. Applying sealant over a damp or dirty surface is like putting a bandage on a muddy arm; it simply won’t stick where it counts.
Next, read the instructions on the can. Different products have different ideal application temperatures, recoat times, and cure times. Use painter’s tape to mask off any areas you don’t want the spray to hit. When you apply it, use smooth, sweeping motions and aim for several thin coats rather than one thick one. A thick coat can trap solvents, preventing the sealant from curing properly and leading to a weak, gummy finish. Give it the full recommended time to cure before exposing it to rain.
An afternoon spent proactively sealing your apartment’s exterior is one of the smartest investments you can make. It’s not just about preventing a water stain; it’s about protecting the structural integrity of your home and avoiding the stress and expense of major repairs. By choosing the right product for the job—whether it’s a pinpoint sealer for a window frame or a penetrating solution for a concrete patio—you take control and ensure your small space remains a safe, dry, and healthy place to live.
