Waterproofing might only be one stage in the build process, but when it fails, it becomes the problem everyone remembers. From blown-out budgets to structural repairs and unhappy clients, waterproofing issues can have serious consequences. Fortunately, most failures stem from avoidable mistakes on site. In this blog, we unpack the most common waterproofing errors seen in construction, and how to avoid them using the right products, techniques and planning.

1. Poor Surface Preparation

Adhesion is everything. If the surface isn’t properly cleaned and dry before application, the membrane won’t bond — leading to bubbling, peeling, or water ingress.

Always ensure surfaces are clean, dry, and structurally sound. Remove dust, dirt and any other contaminants before application. Use a membrane system compatible with your substrate (concrete, screed, fibre cement sheeting, etc.), and follow any cleaning or prep instructions to the letter.

2. Ignoring Movement Joints and Cracks

Covering over control joints or cracks without detailing them properly is a recipe for disaster.

Buildings move. Without flexibility or accommodation for movement, rigid waterproofing layers can crack under stress, leading to leaks right where you need protection most.

Use flexible, high-elongation membranes (like ours) that can bridge cracks and handle substrate movement. Reinforce joints, corners and penetrations with fabric or bandage systems if required by the product specification.

3. Inconsistent Membrane Thickness

Applying waterproofing too thin or too thick in a single coat will compromise your protection.

Too thin and you risk pinholes and weak coverage. Too thick and you could trap moisture or create curing issues. Always apply membranes in multiple coats to the manufacturer’s specified thickness, usually measured in dry film thickness (DFT). Use a wet film thickness gauge to check as you go.

4. Rushing the Curing Process

Do not install new finishes over the membrane or flood test it before it is fully cured. Likewise avoid applying it in an area where it will be exposed to water or rain before it can fully cure.

Early traffic, water exposure, or tiling can damage uncured membranes, especially in cooler or humid conditions where drying takes longer.

Stick to the recommended cure times. Use site conditions (temperature, humidity, ventilation) to guide timing, and always complete a flood test once cured before proceeding with tiling or finishes.

5. Using the Wrong Product for the Application

Using a membrane not suited to the specific environment — like internal-only products used externally, or membranes without chemical resistance in wet areas — is an obvious but surprisingly common mistake.

Not all waterproofing products are created equal. Mismatched systems can degrade, delaminate or become brittle over time.

Choose a membrane with the right ratings and certifications for your job. Our liquid-applied waterproofing system is UV-stable, highly flexible (1300% elongation), and performs across internal, external and below-grade applications.

6. Skipping Manufacturer Guidelines

Don’t apply membranes based on “what we’ve always done” rather than reading the latest spec sheets. Formulations evolve, and assuming you know a product without reading up can lead to incompatibility, missed coverage requirements, or incorrect application methods.

Download the latest TDS and application guides for your product. If in doubt, call the manufacturer or rep. Getting it right now is far cheaper than redoing it later.

Waterproofing is a critical trade. The smallest shortcut or oversight can cost tens of thousands to fix. That’s why it's worth investing in:

• High-performance membranes designed for real-world conditions
• Proper training for your team on how to apply them
• Ongoing support from a technical partner who knows waterproofing inside and out

Ready to protect your next project from leaks, defects and costly call-backs? Explore our liquid membrane system or get in touch with our technical team today to ask any questions.