Choosing the right sealer for cinder blocks is crucial to protect foundations, basement walls, and exterior blockwork from moisture, staining, and freeze-thaw damage. The best products combine barrier strength, breathable or penetrating properties, and ease of application. This guide highlights five reliable sealers and related products that perform well on cinder blocks, concrete blocks, and other masonry surfaces. We compare moisture resistance, durability, and suitability for indoor and outdoor use, helping you pick the right option for your project without overpaying or sacrificing long-term protection.
| Product | Brand | Common Use | Size |
|---|---|---|---|
| Ames Block & Wall Liquid Rubber Waterproofer | AMES | Concrete sealer; basements and foundations | 1 gallon |
| Zinsser Block Filler 2X High Build Primer | Zinsser | Prep for concrete/cinderblock surfaces | 5 gallons |
| MasonryDefender Brick Sealer | MasonryDefender | Brick and masonry walls; interior/exterior | 1 gallon |
| BEEST Foundation Sealant | BEEST | Foundation/seepage waterproofer; indoor/outdoor | 1 gallon |
| Black Diamond Concrete Sealer | Black Diamond Stoneworks | Driveways, patios, brick, stone | N/A |
Ames Block & Wall Liquid Rubber Sealer
Ames Block & Wall Liquid Rubber Waterproofer is a versatile, white coating designed to waterproof concrete surfaces and foundations. It functions as a protective layer that resists moisture intrusion while remaining flexible to accommodate small structural movements. The product is listed as a one-gallon solution, suitable for basements, crawl spaces, and exterior block walls where dampness is a concern. While the product details show a mix of origin notes and a white finish, the primary value lies in forming a durable, watertight film that helps prevent seepage through cinder block walls. It’s a straightforward option for DIY projects and small-scale repairs.
Use considerations include surface cleanliness and dryness prior to application, with typically a brush or roller approach to apply an even coat. For best results, ensure the area is well-ventilated and protected from rain until cured. The coating’s color and coverage characteristics can influence appearance on white or light-colored block walls, so testing on a small area before full application is prudent. This product is especially suited for basements and foundation walls where moisture control is a priority.
Zinsser Block Filler 2X High Build Primer
Zinsser Block Filler 2X High Build Primer is a heavy-duty primer designed to smooth rough concrete, cinderblock, brick, and other masonry surfaces before topcoats. This product emphasizes interior and exterior use with a high-build white finish, capable of filling imperfections and reducing porosity for more even paint or sealant adhesion. It’s particularly valuable when the wall texture or block joints are uneven, allowing subsequent sealers or coatings to perform more consistently. The 5-gallon size is tailored for larger projects or ongoing maintenance programs where repeated sealing or priming is anticipated.
As a prep coat rather than a direct waterproofer, Zinsser Block Filler creates a uniform base that helps any subsequent sealer or paint adhere more evenly. It’s compatible with a range of masonry substrates, including concrete masonry units and mortar joints, making it a versatile option for cinder block remediation. For proper use, follow the manufacturer’s drying times and recoat windows to ensure the layer remains integral before applying final sealers or coatings.
MasonryDefender Brick Sealer
MasonryDefender Brick Sealer is a satin-sheen, water-based acrylic sealer designed to protect brick and masonry walls while preserving the natural look of the material. Suitable for both interior and exterior use, it creates a moisture-repellent surface that enhances cleanliness and makes brick walls easier to maintain. The clear finish maintains the color and texture of bricks, while providing a protective barrier against moisture, cracking, and flaking. This product is well-suited for basements, exterior brick facades, and any cinder block projects where a visible seam or texture should be preserved.
Application involves cleaning and allowing the surface to dry, then applying multiple coats as needed for the desired sheen and protection level. The satin finish provides a balance between sheen and brick aesthetics, ensuring that indoor walls don’t appear overly glossy while still offering moisture resistance. For best results, pair with routine cleaning and periodic re-sealing based on exposure to weather, humidity, and traffic in high-use areas.
BEEST Foundation Sealant
BEEST Foundation Sealant is a contractor-grade, liquid rubber waterproof coating designed to form an impenetrable moisture barrier on foundation walls, basements, and other structural surfaces. It emphasizes a permanent bond and vapor barrier properties, delivering a durable, UV-stable finish that is suitable for both indoor and outdoor applications. The formulation aims to withstand extreme conditions and resist cracking, providing long-term damp-proofing for stone, concrete, brick, and other masonry substrates. This product is especially applicable where continuous damp protection and a hard-wearing film are required, such as exterior foundation walls and interior basement liners.
Considerations include the need for proper surface preparation, ventilation during application, and the anticipated exposure level. Low VOC formulations reduce odor and environmental impact, which is favorable for indoor projects. This sealer can be used across multiple substrates, including wood and metal, broadening its use in mixed-material foundations. The result is a robust, flexible coating designed to resist moisture intrusion across seasons and climate variations.
Black Diamond Concrete Sealer
Concrete Sealer Clear Penetrating Waterproofing Spray by Black Diamond Stoneworks is a water-based sealant designed to penetrate concrete surfaces and provide long-lasting protection against water, salt, and weathering. Its penetrating formula helps reduce moisture intrusion and surface degradation while maintaining a natural look. This spray is practical for driveways, patios, pavers, brick, and other outdoor hard surfaces where a clear, low-profile finish is desired. It’s particularly convenient for larger exterior projects or where uniform penetration across irregular textures is needed, helping minimize staining and freeze-thaw damage on contact blocks and adjacent masonry surfaces.
Application typically involves cleaning, drying, and evenly coating with spray to achieve consistent coverage. The product’s penetrating nature means it may require multiple coats for heavy porous surfaces. It is appropriate for both new and older masonry where surface porosity can vary, providing a protective layer that preserves aesthetic integrity while extending service life during exposure to weather and deicing salts.
Buying Guide
Key purchase considerations
When sealing cinder blocks, consider the substrate porosity, moisture exposure, and whether you need a penetrating seal or a film-forming barrier. Penetrating sealers preserve breathability while reducing water uptake; film-forming options create a moisture barrier but can alter appearance or texture. Surface preparation is essential—remove loose material, mold, and efflorescence, and ensure dry conditions before application. For basements and foundations, prioritize products with strong moisture resistance and compatibility with concrete masonry units. Indoor projects benefit from low odor and low VOC formulations for safer, easier application.
Application methods and compatibility
Sealants and sealers vary by application method: brushes, rollers, or spray systems. Some products are designed specifically for brick or concrete masonry, while others are multipurpose and suitable for wood, metal, and other substrates. Assess whether you need interior or exterior performance, and whether the surface needs a primer such as a block filler before sealing. Ensure the product adheres well to cinder blocks and mortar joints without causing staining or color shifts. Adequate drying and curing times are critical to achieving maximum performance before exposure to moisture.
Durability, coverage, and maintenance
Durability depends on the formula—e.g., water-based acrylics offer easy maintenance and a clean look, while epoxy or rubberized emulsions provide tougher barriers. Coverage rates influence project cost and scheduling; heavy porosity surfaces will use more material. For exterior walls, plan for periodic re-sealing to maintain moisture protection and surface cleanliness. Consider products that offer UV resistance if sun exposure is significant or if the sealer will be exposed to direct weathering. Keep in mind the recoat windows and temperature recommendations to ensure optimal adhesion and longevity.
Safety, regulatory, and environmental considerations
Check VOC content and local regulations, especially for indoor applications or garages connected to living spaces. Low-VOC and water-based options reduce odors and environmental impact, making them suitable for DIY projects and spaces with limited ventilation. Follow manufacturer safety data sheets for handling, ventilation, and curing times. If you work around occupied spaces, choose products with minimal fumes and easy cleanup. Always wear appropriate protective gear and dispose of leftover materials according to local guidelines.
Cost-effectiveness and project fit
Balance upfront cost with expected lifespan and maintenance needs. A higher-quality sealer may require a larger upfront investment but deliver longer protection and less frequent re-sealing. Review the project scope—one-gallon supplies suit small basements or single walls, while larger developments benefit from five-gallon or bulk options. Consider compatibility with additional coatings or primers, especially if you anticipate repainting or applying a secondary sealer down the line. A well-chosen product aligns with both immediate needs and long-term maintenance goals for cinder block work.