Common Issues in Waterproof Coating Application

Achieving a flawless execution in waterproof coating projects is far from being as simple as it seems. It's not just about applying the coating; every step is crucial. Besides selecting high-quality waterproof coatings, understanding the properties of these coatings, adhering to proper techniques, and paying close attention to every detail are essential to ensure a leak-proof outcome. Only through meticulous execution can the waterproofing be done right, ensuring absolute water tightness.

Sagging on Vertical Surfaces

• Definition: Sagging refers to the presence of streaks or cracks on the coating surface after application, commonly seen in JS waterproof coatings on vertical surfaces.
• Cause: Applying the coating too thickly in one go or concentrating the application in a small area.
• Solution: For vertical applications, it's recommended to apply at least three coats to achieve a thickness of 1.5mm. Ensure the roller moves in varied directions to evenly spread the coating, applying vertically then horizontally to avoid sagging.

Coating Peeling from the Base

• Definition: This occurs when the coating easily peels off from the base, especially in large pieces, posing significant risks, particularly on vertical surfaces. This issue is most common during summer.
• Cause: Causes include a loose or dusty base, or the surface strength of the base being lower than the adhesion strength between the coating and the base, coupled with inadequate base wetting or priming before application.
• Solution: Apply a base treatment agent or dilute the waterproof coating for priming. This improves the surface strength of the base and the adhesion between the coating and the base. Priming significantly increases adhesion and full-bond rate between the coating and the base.

Cracking at Flat Surfaces and Inside Corners

• Definition: Cracks on flat surfaces appear as crazing, linear, or triangular openings, while inside corners usually show as long, straight lines over a large area, primarily occurring in cement-based waterproof coatings.
• Cause: Causes for flat surface cracking include a loose base or excessive dust, leading to adhesion failure and shrinkage cracks during curing. Corner cracking mainly occurs when corners are not rounded off, resulting in uneven drying and shrinkage.
• Solution: Clean the base thoroughly before application. Repair loose areas with mortar or leak-stop products. Keep the base moist but not wet, and consider priming to prevent bubbles, pinholes, and cracks. Round off inside corners to a radius of >5cm and apply a thinner layer at these points.

Pinholes and Blistering

• Definition: Numerous small holes appear after application, with some areas blistering. This is common in cement-based waterproof coatings and can extend to all types of coatings.
• Cause: When concrete or the base absorbs water, air trapped inside rises to the surface, forming bubbles. If these bubbles burst after coating application, pinholes result; if not, blistering occurs.
• Solution: Saturate the base with water before application. Dilute materials like JS or acrylic coatings for a base layer to seal pores. For K11/mortar products, saturating the base is most effective. Applying a base treatment agent can also address this issue.

Sand Loss and Powdering

• Definition: After curing, touching the material surface causes sand to fall or leaves dust on the hand, indicating low surface strength. This is often seen in K11/mortar products and cement-based crystalline waterproof coatings.
• Cause: Usually due to incorrect water-to-cement ratio or the material being washed by water before curing.
• Solution: Follow packaging instructions for two-component mortars; water addition should not exceed 20% of the liquid component. For single-component mortars, a water-to-mortar ratio of 21~23:100 is appropriate; for cement-based crystalline waterproof coatings, a water-to-crystalline ratio of 0.3:1 is recommended, with some flexibility within manufacturer guidelines.

Settlement After Mixing

• Definition: Two-component materials or single-component mortars show separation after mixing, with a milky liquid on top and sediment at the bottom.
• Cause: Often due to incorrect water-to-cement ratio, with excessive water exceeding the emulsion's carrying limit, disrupting the material's stability.
• Solution: Adhere strictly to mixing ratios. For two-component mortars, adding up to 20% water of the liquid component is acceptable for ease of application; for single-component mortars, a water-to-mortar ratio of 21~23:100 is suitable; for cement-based crystalline waterproof coatings, a water-to-crystalline ratio of 0.3:1 is advised, within the limits set by the manufacturer.

Delayed Curing

• Definition: The material does not cure for an extended period (a week or more), or the surface dries but blisters or wrinkles appear during water tightness tests, commonly occurring with acrylic waterproof coatings.
• Cause: Acrylic waterproof coatings cure by water evaporation. In closed, humid spaces with poor air circulation, curing may be significantly delayed.
• Solution: Avoid using acrylic waterproof coatings in closed or humid spaces. If already applied, enhance air circulation and raise the ambient temperature to promote curing. If uncured material causes issues in water tightness tests, remove the entire waterproof layer and apply a two-component coating.

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