Concrete is one of the most durable and versatile construction materials in the world — it’s used everywhere. However, its porosity makes it vulnerable to water damage, which can compromise its structural integrity over time. Waterproofing concrete is crucial for extending its lifespan. In this blog post, we’ll explore the importance of waterproofing concrete, methods to do so, and tips for long-term protection.

Why Waterproof Concrete?

Concrete’s porous nature allows water to seep in, leading to potential problems like:

• Cracks and deterioration as it expands and contracts with temperature changes.
• Corrosion and rusting of steel reinforcements.
• Mould and mildew growth in damp environments.
• Reduced lifespan and premature wear.

Proper waterproofing ensures that the material remains robust and safe, even in challenging environmental conditions. By protecting against weather, chemicals, and wear; you can prevent costly repairs and replacements, as well as maintain the strength of buildings and infrastructure.

Signs Your Concrete Needs Waterproofing

Even the most durable concrete can show signs of wear and vulnerability over time. Recognising these signs early can help prevent extensive damage and costly repairs. Here’s what to watch out for:

• Visible cracks
• Water stains and efflorescence — a white powdery deposit on the surface of concrete caused by water carrying minerals to the surface as it evaporates.
• Surface damage like flaking, chipping, or peeling.
• Mould, mildew or must smells
• Rust stains — which come from the corrosion of steel reinforcements
• Pooling water
• Increased humidity indoors (for structures with concrete walls or foundations)
• Discolouration or dark patches

Methods for Waterproofing Concrete

There are several effective ways to waterproof concrete, depending on the specific application and exposure. Here are the most common methods:

1. Concrete Sealers

   Sealers are liquid compounds applied to the surface of concrete. Penetrating Sealers absorb into the concrete and block pores to prevent water ingress. Non-Penetrating Sealers create a protective layer on the surface, ideal for high-traffic areas.

2. Crystalline Waterproofing

   Crystalline technology works by forming insoluble crystals within the concrete’s pores and cracks when exposed to water.

3. Sheet Membranes

   Durable and pre-formed layers applied to concrete surfaces.

4. Waterproofing Admixtures

   Mixed into the concrete at the batching stage, these admixtures reduce its permeability.

5. Epoxy and Polyurethane Coatings

   These are highly effective in sealing cracks and providing a waterproof barrier.

6. Liquid Membrane Systems

   Applied like paint, these create a seamless and flexible barrier. This is becoming every home owner’s preferred method for waterproofing as it’s an easy, fast, and durable DIY solution.

   Our SEMCO Liquid Membrane™ also has the added benefit of advanced crack bridging properties, so it can be used to repair, stabilise, and waterproof damaged concrete. Here’s more about the advantages of liquid waterproofing systems.

Best Practices for Waterproofing Concrete

• Check for cracks or signs of water damage to address issues early.
• Ensure the concrete is dry, clean, and free of debris before applying waterproofing materials.
• Match the waterproofing solution to the structure's environment and usage.
• Proper drainage systems complement waterproofing efforts by directing water away from the structure; make sure faulty drainage systems are repaired prior to waterproofing for best results.

Waterproofing concrete isn’t just a construction step; it’s a safeguard for the future. Whether you’re working on a new project or maintaining an existing structure, investing in waterproofing pays dividends in longevity and peace of mind. Looking to waterproof your concrete? SEMCO Liquid Membrane™ is an easy DIY solution.

How to Waterproof Concrete with a Liquid Membrane

We have specific installation guides for our product per substrate here, but in general the following steps are involved in waterproofing concrete.

Step 1: Preparation

To clean the concrete, ensure your surface is free of any debris. Use a specialised cleaner and scrub the surface using a scrub machine or nylon brush. You will need to scrub and rinse multiple times to ensure a completely clean surface. Always let surface completely dry prior to application of waterproofing.

Optional: Fabric Reinforcement

If you have any wide cracks, a Fabric Reinforcement is needed to bridge the crack. Every product will have different guidelines; our SEMCO Liquid Membrane™ can be applied to cracks smaller than 6mm wide.

Step 2: Masking

Mask off areas that are not receiving any coating. Remove masking tape before material has fully cured.

Step 3: Application

• We recommend a roller for concrete applications. Apply your first coat of liquid waterproofing. Check product guidelines for the recommended thickness of coats.
• Once you can walk on the surface and not get any residue on your shoe or feet, or cannot leave a fingerprint impression, it is ready to re-coat.
• Apply the second coat in an alternate direction over the first coat.
• Let topcoat dry to the touch. Again, every product is different. SEMCO Liquid Membrane™ has a very fast drying time — for concrete, most projects will be dry in 1 hour.
• When the last coat has dried to the touch, inspect final surface for pinholes, voids, or thin spots. You can just roll over these areas.
• SEMCO Liquid Membrane™ will become a lighter colour when it’s fully dry.
• Curing time depends on temperature, humidity and airflow, however typically initial cure is within 6 - 7 days as per specific product recommendations.