¿Ra mahyoni ga humedecer ar impermeabilización flexible??

When constructing flexible waterproof coatings (such as polymer cement-based waterproof coatings, polyurethane waterproof coatings, etc.), the wetness requirements of the base surface need to be determined according to the specific material type and construction environment, but generally follow the following principles:

1. Cement-based flexible waterproofing (such as JS waterproof coatings, K11 waterproof slurry, etc.)

   • The base surface needs to be moist but without obvious water:This type of material usually requires the base surface to remain moist but without water accumulation (commonly known as “dry surface and wet inside”).

   • A moist base surface helps the waterproof slurry to better bond with the base layer, and prevents the dry base surface from absorbing moisture too quickly, causing the coating to crack or powder.

     Operation suggestions: Sprinkle water to moisten the base surface before construction, and apply it after there are no obvious water droplets on the surface.

2. Polyurethane flexible waterproofing (single/double component)

   • The base surface needs to be dry:Polyurethane coatings are sensitive to moisture, and the base surface needs to be thoroughly dry (the moisture content is usually required to be ≤8%), otherwise bubbles and delamination are likely to occur.

   • Exception: Some modified polyurethanes (such as moisture-curing types) can be applied on damp substrates, but they must be operated strictly according to the product instructions.

3. General precautions

   • Base treatment is a priority:Whether wet or dry, the substrate must be firm, flat, free of oil and loose materials. Cracks and holes must be filled with repair mortar first.

   • Ambient temperature and humidity:Avoid construction in high temperature and windy weather to prevent water from evaporating too quickly (cement-based materials) or abnormal curing (polyurethane).

   • Product instructions shall prevail:Different brands and types of waterproof materials may have different requirements, so be sure to follow the construction guide provided by the manufacturer.

Summary suggestions

• Cement-based flexible waterproofing: The substrate is more reliable to wet, but there is no visible water on the surface.

• Polyurethane waterproofing: The substrate must be dry.

• Test method: Use absorbent paper to stick to the substrate. If there is no obvious water stain, it is in the “no visible water” state

• Be sure to confirm the material properties before construction and do a small area test to ensure the bonding effect!

If the base surface is not moistened as required when constructing flexible waterproof coatings (especially cement-based waterproof materials), the following problems may occur:

1. Cement-based flexible waterproofing (such as JS/K11 coatings)

   • Decreased adhesio

     • The dry base surface will quickly absorb the moisture in the waterproof slurry, resulting in the coating being unable to fully hydrate, and the adhesion to the base layer is not strong, which is prone to hollowing and delamination.

     • Phenomenon: After completion, the coating may be torn or knocked by hand, and the entire piece may peel off.

2. Cracks or powdering of the coating

   • After excessive moisture is absorbed, the coating cannot complete the curing reaction due to lack of water, and the surface dries too quickly, forming cracks or loose powder layers.

3. Failure of waterproof performance

   • Micro cracks and hollows will form water seepage channels, and water may penetrate from weak points, causing the overall failure of the waterproof system

4. Polyurethane waterproof coatings

   • Less impact from dry substrate

     • Polyurethane itself requires a dry substrate, but if the substrate is too dry and porous (such as an old cement substrate), it may be necessary to first apply a primer (such as epoxy primer) to seal the pores, otherwise:

     • The coating will penetrate too much into the substrate, resulting in insufficient thickness

     • If the dust on the substrate is not cleaned, the adhesion will be reduced.

5. Special circumstances (high temperature/windy environment)

   • Even if the material itself does not require high moisture content (such as some acrylic coatings), in hot and windy weather, a dry substrate will accelerate the evaporation of moisture from the coating, resulting in:

   • Shrinkage and cracking of the coating;

   • Discontinuous film formation and pinholes

How to remedy an unmoistened substrate?

1. Cement-based waterproofing: Stop construction immediately, spray water on the painted area for maintenance (if the initial setting is not complete), or scrape it off and re-moisten the substrate before construction

2. Polyurethane waterproofing: Ensure that the substrate is dry and dust-free, and polish and apply a special primer if necessary

Key conclusions

• Cement-based waterproofing: Not wetting the base surface ≈ “letting the coating die of thirst”, directly damaging the bonding and strength

• Other materials: The base surface must be treated strictly according to the product requirements, dry ≠ no treatment (cleaning and leveling are still required

• Ultimate advice: Before construction, wipe the base surface with a wet sponge to achieve a “saturated dry surface” state (no visible water, slightly cool to the touch) for the safest.