What is waterproof cement coating?

Waterproof cement coating is a protective barrier applied to concrete surfaces to prevent water intrusion and damage. It creates a water-tight seal that protects the underlying concrete from moisture, salts, and other corrosive elements. Waterproof coatings are essential for concrete structures like basement walls, foundations, bridges, dams, and tunnels that are exposed to wet environments.

What are the benefits of waterproof cement coating?

There are several key benefits to using a waterproof cement coating:

• Prevents water damage: Waterproof coatings prevent moisture from seeping into porous concrete and causing erosion, cracks, staining, and other damage.
• Protects reinforcement: The coating safeguards any steel reinforcement bars inside the concrete from corrosion.
• Extends service life: By preventing water damage, a protective coating can significantly extend the useful service life of concrete structures.
• Aesthetic appeal: Waterproof coatings provide an attractive uniform appearance and prevent unsightly staining on decorative concrete surfaces.
• Versatility: Coatings can be applied to old and new concrete, vertical and horizontal surfaces, above and below grade.
• Enhances durability: The coating makes concrete more durable and resilient against freeze-thaw cycles, chemical exposure, and abrasion.

What materials are used for waterproof cement coatings?

There are several major types of materials used to create effective waterproof coatings for concrete:

Acrylics

Water-based acrylic coatings provide excellent adhesion, UV resistance, and waterproofing. They penetrate deeply to seal concrete pores. Acrylics are flexible, allowing for movement and cracking. They can be tinted and are easy to apply with a sprayer, roller, or brush.

Epoxies

Two-part epoxy systems form a rigid, adhesive coating with excellent chemical and abrasion resistance. Epoxies are among the strongest and longest-lasting waterproof cement coatings. They bond tenaciously to concrete and can withstand heavy traffic.

Polyurethanes

Polyurethane coatings contain reactive polymers that fully cure to form a seamless, elastic waterproof membrane. Polyurethanes stretch with the concrete so they won’t crack or peel. They provide superior UV resistance and durability.

Polyurea

Polyurea coatings are formed by mixing reactive polyurethane resins and amines. They cure rapidly to form a rubber-like, flexible coating. Polyureas easily bridge cracks and provide thermal insulation. They have a very long life span.

Cementitious coatings

Cement-based waterproof coatings are blended with polymers, aggregates and reinforcing fibers. They chemically bond with the concrete to provide excellent adhesion. Cement coatings are vapor permeable, allowing concrete to breathe.

What are the different types of waterproof cement coatings?

Waterproof cement coatings come in different compound variations to suit specific performance requirements:

Acrylic coatings

• Pure acrylic – 100% acrylic resin content, provides maximum durability and longevity.
• Styrene acrylic – Contains styrene for better water resistance and adhesion.
• Silicone-modified acrylic – Silicone additive helps coating expand and contract to resist cracking.
• Elastomeric acrylic – Extremely flexible and elongating, able to bridge cracks up to 1/16 inch.
• Aliphatic acrylic – Provides maximum UV protection and color retention.

Polyurethane and polyurea coatings

• Aromatic – General purpose, economical option.
• Aliphatic – Superior UV stability, non-yellowing.
• Hydrophobic – Repels water and resists moisture vapor transmission.
• Hypalon – Excellent chemical resistance.

Epoxy coatings

• 100% solids epoxy – Zero VOC, low odor, thick film build.
• High-build epoxy – Heavily loaded with pigments and fillers.
• Fast-set epoxy – Quick-curing formula.
• Moisture-tolerant epoxy – Can be applied to damp concrete.

Cementitious coatings

• Acrylic-modified – Enhanced adhesion and resistance.
• Polymer-modified – Improved flexibility and longevity.
• Fiber-reinforced – Increased tensile strength.
• Corrosion-inhibiting – Reduces corrosion of rebar.

What is the application process for waterproof cement coatings?

Applying a waterproof coating to concrete involves careful surface preparation followed by coating application in these basic steps:

1. Surface preparation – Concrete must be clean and dry. Remove all dirt, oils, curing compounds, loose paint and unsound concrete. Etch smooth surfaces. Repair cracks and holes.
2. Priming – For maximum adhesion and penetration, prime all surfaces with a concrete primer or base coat.
3. Detail work – Seal around drains, joints and corners with waterproofing tape or liquid membrane.
4. Coating application – Apply coating according to manufacturer specifications, using short nap rollers, brushes or airless spray.
5. Second coat – For thicker coverage, apply a second coat after proper drying time.
6. Inspection – Check for pinholes, thin spots, and make repairs as needed to ensure continuous protection.

Proper surface prep and following product specifications for film thickness, recoat times, and curing conditions are vital for successful waterproofing performance.

How much does it cost to apply a waterproof cement coating?

Waterproof cement coating costs typically range from $2-$7 per square foot depending on the product type and surface conditions. The total project cost is influenced by:

• Coating type – Higher-performance polyurea and polyurethane systems cost more than acrylics.
• Surface prep – Extensive repairs or smooth surface etching increases labor time.
• Accessibility – Coating tunnels, reservoirs and other hard to reach surfaces raises the cost.
• Application method – Spraying is faster than rolling but requires renting equipment.
• Coats needed – Second coats add more material cost.
• Contractor rates – Prices vary based on location and company size.

In addition to the coating itself, factors like permit fees, scaffolding/containment, and surface repairs can influence the total installed price. Get multiple estimates to compare contractor rates.

What are the limitations of waterproof cement coatings?

Waterproof cement coatings have the following drawbacks and limitations:

• Surface defects – Any cracks, holes or imperfections can lead to water intrusion if not properly repaired.
• Thickness – Insufficient film build leaves concrete vulnerable to moisture.
• UV exposure – Long-term sun exposure degrades some coating types.
• Chemical contact – Coatings have varied resistance to fuels, oils and cleaners.
• Freezing weather – Application is difficult below 40°F/4°C for most coatings.
• Curing conditions – Ideal humidity and temperature is required for proper curing.
• Difficult access – Applying coatings in cramped spaces is challenging.
• Surface wear – Abrasion can gradually erode the protective coating.

Proper product selection, surface preparation and application help maximize coating effectiveness and longevity.

How do you choose the right waterproof cement coating?

Selecting the optimal waterproof cement coating involves considering these key factors:

Performance Requirements

• Surface location – Above or below grade? Immersed or atmospheric exposure?
• Moisture levels – Hydrostatic pressure involved? Vapor transmission rate?
• Exposure conditions – Chemicals? Extreme heat or cold? Heavy traffic?
• Durability needed – Years or decades of protection?
• Crack bridging – Minimal or wide crack flexibility required?

Concrete Conditions

• Age and quality – Newly poured or old, weathered concrete?
• Surface texture – Smooth, porous or rough profile?
• Presence of defects – Cracks, spalls, holes that need repair?
• Prior coatings – Compatibility with existing layers?

Project Details

• Accessibility – Ease of application to the surface?
• Timeframe – How soon before use is required?
• Appearance – Gloss/sheen and color preferences?
• Budget – Material costs and labor rates to consider.

Consulting with an experienced coating manufacturer ensures you select the right product and system to provide maximum, long-lasting waterproof protection.

What are the different finish options for waterproof cement coatings?

Waterproof cement coatings are available in a range of aesthetic finish options:

• Gloss – Glossy, light-reflective surface. Enhances colors and makes stains easy to clean.
• Satin – Some sheen but not highly reflective. Provides a finish between gloss and flat.
• Matte – Flat, non-reflective finish. Hides imperfections well.
• Textured – Small texture adds slip resistance and visual appeal.
• Clear – Transparent, minimal appearance change. Shows natural substrate color.
• Pigmented – Can be tinted to any color for decorative appeal.
• Seamless – Smooth, uniform appearance without joints.

Consider the degree of sheen, texture and color desired for the project. Gloss and darker pigmented coatings show more surface defects. Clear and matte coatings hide flaws better. Review finish options with the manufacturer to select the ideal aesthetic.

What are other common questions about waterproof cement coatings?

How long does a waterproof coating last?

With proper surface preparation and application, quality acrylic, polyurethane, epoxy and polyurea coatings typically last 10-30 years before needing reapplication. Cementitious coatings last 5-15 years. Coating life depends on thickness applied, exposure conditions and surface traffic.

Can you apply a waterproof coating over old paint?

Coatings are often compatible with existing paint or coatings after proper cleaning and priming. However, extensive peeling or flaking paint should be removed for best results. Always check with manufacturer about application over old paint.

How soon can I expose the coating to water?

Curing times before water exposure vary by product but are typically 24-72 hours after application at 70°F (21°C). Full cure for concrete immersion is 5-7 days. Confirm exact cure times with the coating manufacturer.

How are waterproof cement coatings tested?

Testing evaluates characteristics like tensile strength, adhesion, abrasion resistance, UV stability, crack bridging ability and water permeability. Common standard test methods include:

• ASTM D4541 – Pull-off strength of coatings using portable adhesion testers.
• ASTM D4060 – Abrasion resistance measured by Taber abraser machine.
• ASTM D2370 – Elongation and tensile strength with dumbbell specimens.
• ASTM D1653 – Moisture vapor transmission through coated concrete.
• ASTM C836 – Determining thickness using magnetic gages.

Manufacturers should provide data on coating properties using standardized industry test procedures.

How are waterproof cement coatings repaired?

Repairs depend on the damage extent. For small damaged areas, clean and abrade the coating surface then reapply the product following original specifications. For extensive damage, the existing coating may need complete removal and reapplication. Consult the manufacturer for proper repair procedures.

Conclusion

Waterproof cement coatings provide a critical barrier to protect concrete structures against water damage and deterioration. Choosing the right coating for specific project needs and conditions is key to achieving long-lasting, effective waterproofing performance. With proper surface preparation and application, quality coatings can extend the service life of new and existing concrete for decades.