How to Waterproof Concrete with Epoxy?

Written By Adam Paul - Waterproofing Expert

Epoxy is a successful concrete waterproofing method. Epoxy creates a highly water resistant, nonbreathable, solid, UV resistant, slip resistant, thermal and electric insulated, less flexible layer on the concrete. It helps to protect the concrete surface from water related damages and increases the structural integrity over time.

When you apply epoxy on the concrete surface we highly recommend you to follow these 8 steps to be more efficient and last longer. This is the recommended method from the Aqviz experts.

8 Steps to Waterproof Concrete With Epoxy

1. Clean the concrete surface
2. Prepare the concrete surface
3. Apply the primer to the concrete
4. Mix the epoxy resin and hardener
5. Apply the Epoxy on the concrete surface
6. Allow epoxy for curing
7. Apply the second coating if needed
8. Protect the epoxy waterproofing layer

Below is a detailed guide to our recommended method. Please let us know if you have any problems related to this method. 

1. Clean the Concrete Surface

As the first step, we should clean the concrete surface before applying epoxy waterproofing on the concrete surface. We must ensure that the concrete surface is thoroughly cleaned and that any dust, dirt, grease, oil, or previous coatings do not remain. Because we have experienced these residues can interfere with the epoxy’s adhesion and it lead to peeling or weak the waterproofing layer. 

5 Steps to clean concrete before Epoxy application

1. Remove loose debris on the concrete surface: Use a broom, vacuum, or blower to remove dust, dirt, and any loose particles on the concrete surface.
2. Degrease oil and stains on the concrete surface: If there are grease or oil stains on the concrete surface, we use a heavy-duty degreaser or a mixture of trisodium phosphate (TSP) and warm water to scrub the area. 
3. Use a pressure washer: We recommend using a pressure washer (at least 3,000 PSI) for exterior concrete surfaces to remove embedded dirt and contaminants.
4. Apply a mild acid wash if needed: we itch the concrete surface with a diluted acidic solution (10:1 water-to-acid ratio) for tough stains and mineral buildups. However, we rinse the surface thoroughly after acid washing to neutralize any residue.
5. Let the surface dry after the cleaning process.

Tip from the Aqviz: If there are any previous coatings, sealants, or paint, you should strip them off using a chemical stripper or a floor grinder to expose the raw concrete surface.

If you have more questions about concrete waterproofing using epoxy, this guide Ultimate Guide for Epoxy Waterproofing on Concrete will help you to conduct it as an expert.

2. Prepare the Concrete Surface

Once the concrete is clean, we must prepare it properly to ensure the epoxy bonds effectively. So Aqviz experts follow the below step by step guide to prepare the concrete surface smoothly.

Steps to Prepare Concrete for Epoxy Waterproofing

Inspect the surface for cracks, pits, or uneven areas.

•  Small cracks (less than 1/8 inch) can be filled with an epoxy patching compound. Larger cracks may require a cementitious repair mortar.

Ensure proper surface roughness

We follow these methods to have proper surface roughness.

• Diamond grinding: Diamond grinding is the most effective way to open up the concrete pores and remove the top layer for better adhesion.
• Shot blasting: Shot blasting for large areas, this method roughens the surface and removes weak top layers.
• Etching with acid: Etching with acid is best mechanical grinding is not an option, we use an acid etching solution to slightly roughen the surface.

Let the concrete surface dry

•  If we see any condensation forms underneath the concrete needs we use a moisture barrier primer.

Vacuum and remove dust on the concrete surface

Ensure the surface is completely dry 

You should be patient in the preparation stage. Because a poorly prepped surface can cause peeling, bubbles, or delamination of the epoxy later on.

3. Apply the Primer on the Concrete

An epoxy primer is a specially formulated bonding agent applied before the main epoxy coat to enhance adhesion to the concrete substrate and ensure a strong, long-lasting waterproofing system. Primers seal the pores, reduce moisture transmission, and prevent the formation of bubbles in the epoxy layer.

You can apply primer by following these 5 steps.

• Choose the right primer for the concrete, based on the moisture levels and the type of epoxy system being used. You can see solvent-based, water-based, and 100% solid epoxy primers in the market.
• Before applying the primer, ensure the surface is completely dry, free of dust, oil, and debris.
• Mix the primer thoroughly according to the manufacturer’s instructions
• Apply with a roller or brush. Normally we use a nap roller (3/8" to 1/2") or a brush for edges.
• Allow the epoxy primer for curing. It will take 4 to 8 hours of drying before applying the main epoxy layer. 

Pro Tip: For high-moisture areas, we use a moisture-blocking epoxy primer to prevent hydrostatic pressure from causing peeling.

If you do not use a primer, epoxy may not adhere properly. It leads to peeling, delamination, or a weak waterproofing layer on the concrete. 

4. Mix the Epoxy Resin and Hardener

Epoxy coatings consist of two main components: epoxy resin and epoxy hardener. Epoxy resin is the primary base material that gives epoxy its adhesive and protective properties. Epoxy hardener is the curing agent that chemically reacts with the resin to form a tough, durable, and waterproof surface.

Without the hardener, the resin will remain in liquid form and never cure. Hence epoxy resin and epoxy hardener should be mixed together. The chemical reaction between them ensures the epoxy becomes solid, strong, and resistant to water and chemicals.

Importance of Proper Mixing

Incorrect mixing of resin and hardener can lead to soft spots, improper curing, bubbling, or poor adhesion. That’s why we always mix in the right proportion and method.

We follow these steps when we mix epoxy resin and hardener.

1. Check the mixing ratio: The standard ratio for most epoxies is 2:1 (resin to hardener), but some products may require 1:1 or 3:1. We always follow the manufacturer’s specifications.
2. Use a clean mixing container: A plastic or metal bucket works best. We avoid paper cups or wood sticks, as they can introduce contaminants.
3. Measure accurately: Using a measuring cup, we pour the exact amount of resin and hardener. Even a slight imbalance can affect curing.
4. Mix thoroughly: We use a drill mixer or a paddle mixer to stir the components for at least 3–5 minutes, ensuring no streaks or unmixed parts are left.
5. Pour into another container (double-mixing method): After initial mixing, we transfer the mixture into a second container and mix again to ensure even consistency.

How Long Can Epoxy Be Used After Mixing?

The pot life of mixed epoxy varies from 20 to 50 minutes, depending on temperature and brand. Once mixed, epoxy starts reacting immediately, so we never let it sit too long in the bucket.

How Much Epoxy Should I Mix at a Time?

Mix only as much as you can apply in 30–40 minutes to prevent premature curing if you are working in small sections or hot weather. But for larger areas you can mix bigger quantities but ensure continuous application to avoid uneven curing.

Pro Tip: Warmer temperatures shorten the pot life, so we mix smaller amounts in hot conditions to avoid waste.

5. Apply the Epoxy on the Concrete Surface

After mixing the epoxy resin and hardener, we must apply it immediately to ensure a smooth, even coat before it starts curing. Proper application is essential for creating a durable, waterproof, and long-lasting protective layer over the concrete.

These are the 7 steps that we follow when we apply epoxy on concrete surfaces.

1. Ensure the primer is dry 
2. Divide the area into sections to maintain a consistent thickness and prevent uneven curing.
3. Pour the epoxy onto the floor directly onto the concrete in a ribbon-like pattern to ensure an even spread.
4. Use a notched squeegee or trowel to spread the epoxy on the concrete surface. 
5. Backroll the epoxy in crisscross motions to remove air bubbles and ensure uniform thickness.
6. Work quickly and smoothly: Since epoxy begins curing within 30–50 minutes, we maintain a steady workflow to avoid inconsistencies.
7. Use a spike roller if bubbles form due to trapped air, we use a spike roller to release them before the epoxy sets.

Pro Tip: If applying epoxy on vertical surfaces, we use a thixotropic (non-sag) epoxy or apply thin layers to prevent dripping.

6. Allow Epoxy for Curing

After applying the epoxy layer, it should be cured as per the manufacturer's guidelines. Normally, epoxy has 3 main curing stages such as initial curing, partial curing, and full curing.

• Initial cure (Tack-Free Time): 4-12 hours - The surface becomes dry to the touch but is still soft.
• Partial cure: 12-24 hours - The epoxy is hard enough to walk on but not fully set.
• Full cure: 5-7 days - The epoxy reaches maximum strength and waterproofing properties.

You should be aware of this, In colder conditions, curing takes longer, while in warmer environments, it speeds up.

Tips for proper Epoxy curing

1. Avoid foot traffic on concrete surfaces for at least 24 hours 
2. Wait 5-7 days before heavy use 
3. Control temperature and humidity in the surface area
4. Use a curing accelerator if needed 

Pro Tip: If applying a second coat, we wait within the recoat window (6–24 hours) to avoid sanding. If more than 24 hours pass, we lightly sand the surface to improve adhesion before applying the next layer.

Tools and Materials Needed to Waterproof Concrete with Epoxy

For a successful epoxy waterproofing application, we need the right tools and materials to ensure a smooth process and a durable finish. Each tool and material is used for specific tasks. As experts, we use the below tools for these tasks.

Tools and tasks for concrete cleaning

1. Broom & dustpan to remove loose dirt and debris on the concrete.
2. Shop vacuum to eliminate fine dust and particles on concrete surfaces.
3. Degreaser or trisodium phosphate (TSP) to break down grease and oil stains on the concrete surface.
4. Pressure washer (3,000+ PSI) to clean deeply embedded dirt (for outdoor concrete).
5. Scrub brush or stiff-bristle broom to remove tough stains on the concrete.
6. Muriatic acid (for etching, if necessary) opens concrete pores for better adhesion.
7. Water hose for rinses off cleaning solutions.

Tools and tasks for concrete surface preparation

1. Diamond grinder or floor buffer with sanding discs to roughen the concrete surface for better adhesion.
2. Shot blaster (optional) for large areas to create a rough profile.
3. Crack filler (epoxy-based or cementitious) to repair cracks and holes in the concrete.
4. Putty knife or trowel to spreads repair material into cracks.
5. Moisture meter to check for excessive moisture in the concrete.

Tools and tasks for epoxy application on concrete

1. Nap roller (⅜" to ½") to apply primer on the concrete surface.
2. Paintbrush (for edges and corners) to reach tight areas where rollers can’t access.
3. Gloves and protective goggles to protect eyes from particles and chemicals

Materials for epoxy waterproofing on concrete

1. Suitable epoxy resin and hardener as waterproofing membrane.
2. Epoxy primer (solvent-based or moisture-resistant) to seal concrete pores and prevent bubbling.
3. Mixing container for combining primer components.
4. Stirring stick or drill mixer to mix primer resin and hardener.