Description
Sika Thoroseal 581 (Formerly MasterSeal 581) – 50 lb.
Cement-Based Waterproofing & Air Barrier Coating for Concrete, Masonry & Below-Grade Applications
Protect concrete and masonry structures from moisture intrusion with Sika Thoroseal-581 (formerly MasterSeal 581), a premium Portland cement-based waterproofing coating engineered to provide long-lasting protection against water penetration, air infiltration, and hydrostatic pressure. Polymer-modified with Sika Thoroseal Acryl 60, this high-performance coating creates a durable, breathable waterproof barrier for both interior and exterior applications.
Designed for use on concrete, block, brick, and porous stone, Sika Thoroseal-581 resists both positive and negative hydrostatic pressure, making it an ideal solution for below-grade waterproofing, foundations, retaining walls, basements, water treatment facilities, cisterns, tunnels, and other demanding construction projects.
Unlike traditional waterproof coatings, Thoroseal-581 remains breathable, allowing trapped moisture vapor to escape while preventing water intrusion, helping to reduce the risk of blistering and coating failure.
Key Features & Benefits:
- Advanced Waterproofing Protection – Helps prevent water intrusion, dampness, and moisture damage in concrete and masonry structures
- Effective Air Barrier – Reduces air infiltration to improve building envelope performance
- Resists Positive & Negative Hydrostatic Pressure – Ideal for below-grade waterproofing and water-retaining structures
- Breathable Cement-Based Coating – Allows moisture vapor to escape without compromising waterproof protection
- Polymer-Modified with Sika Thoroseal Acryl 60 – Improves adhesion, flexibility, and long-term durability
- Compatible with Architectural Finishes – Can be coated with many high-performance paints, textured coatings, and decorative finishes
- Conceals Minor Surface Imperfections – Helps improve the appearance of architectural concrete and masonry
- NSF/ANSI Standard 61 Certified – Approved for potable water contact applications
- Suitable for Interior & Exterior Use – Performs in both above-grade and below-grade environments
Product Specifications:
- Brand: Sika
- Product: Thoroseal-581 (Formerly MasterSeal 581)
- Container Size: 50 lb. Bag
- Product Type: Cement-Based Waterproofing & Air Barrier Coating
- Base Material: Portland Cement (Polymer-Modified)
- Shelf Life: 1 Year (Properly Stored)
Set Times
- Initial Set: Approximately 10 minutes at 70°F (21°C) and 50% relative humidity
- Final Set: Approximately 90 minutes at 70°F (21°C) and 50% relative humidity
Coverage:
Coverage will vary depending on substrate texture and porosity.
- Base Coat: Up to 225 sq. ft. per 50 lb. bag at a 1/16" dry film thickness
- Top Coat: Up to 450 sq. ft. per 50 lb. bag at a 1/32" dry film thickness
Recommended Substrates:
Suitable for application over:
- Cast-in-place concrete
- Precast concrete
- Concrete block (CMU)
- Brick
- Porous natural stone
- Masonry surfaces
Ideal Applications:
Sika Thoroseal-581 is recommended for:
- Basement waterproofing
- Foundation walls
- Retaining walls
- Concrete walls
- Concrete block walls
- Bridges and tunnels (non-traffic-bearing surfaces)
- Water cisterns
- Water treatment facilities
- Potable water tanks
- Flashing rough concrete and masonry openings
- Above-grade and below-grade waterproofing
- Interior and exterior masonry protection
Why Choose Sika Thoroseal-581?
For decades, Thoroseal has been trusted by contractors, engineers, and waterproofing professionals to protect concrete and masonry from water infiltration and structural deterioration. Now backed by Sika's advanced technology, Thoroseal-581 continues that legacy with enhanced polymer performance, outstanding durability, and reliable protection against challenging moisture conditions.
Its ability to withstand both positive and negative hydrostatic pressure makes it an excellent choice for below-grade applications where conventional coatings often fail. Combined with its breathable design and compatibility with decorative architectural finishes, Thoroseal-581 offers a complete waterproofing solution for residential, commercial, and industrial construction projects.
Professional-Grade Waterproofing You Can Trust
Whether you're waterproofing a basement, protecting a foundation, sealing a retaining wall, or coating a potable water tank, Sika Thoroseal-581 delivers the long-lasting moisture protection, air barrier performance, and durability professionals rely on for demanding concrete and masonry applications.
Stop Moisture Before It Becomes a Problem.
Choose Sika Thoroseal-581 (Formerly MasterSeal 581) – 50 lb. for proven waterproofing performance, superior hydrostatic pressure resistance, and dependable protection for concrete and masonry structures in even the toughest environments.
