Silicone sealant is an indispensable material in construction and renovation projects. In Hong Kong's humid climate and diverse building environment, selecting the right sealant product is crucial for ensuring project quality and durability. This article provides an in-depth look at various types of sealants, their features, applications, and recommended products to help you make the best choice.
Sealant Classification and Properties
Neutral Cure Sealants
Neutral cure sealants are the most popular sealing products on the market. Their neutral curing process produces no corrosive by-products, making them suitable for metal, glass, stone, and many other substrates.
Key features:
- Neutral cure, non-corrosive to substrates
- Excellent weather resistance and anti-ageing performance
- Good adhesion to multiple materials
- Low odour, construction-friendly
Specialist Sealants
Specialist sealants are developed for specific application environments such as swimming pools and exterior walls, offering targeted performance advantages.
Key features:
- Designed for specific environments
- Special resistance properties (e.g. chlorine resistance, UV resistance)
- Excellent long-term stability
- Compliant with industry-specific standards
Detailed Product Analysis by Brand
Dowsil 791 Silicone Weatherproofing Sealant
Product features:
- Single-component, medium modulus, neutral cure
- +/-50% joint movement capability
- Outstanding weather resistance - virtually unaffected by sun, rain, snow, and ozone
- Low odour, eco-friendly formulation
- Low embodied carbon, meeting sustainability requirements
Applications:
- General waterproof sealing joints
- Glass and curtain wall weatherproofing joints
- Building exterior wall sealing joints
Why we recommend it:
Dowsil 791 is the top choice for an all-purpose neutral sealant, particularly suited to Hong Kong's variable climate conditions. Its superior weather resistance ensures long-term performance.
Dowsil 795 Structural Glazing Sealant
Product features:
- High weather resistance, UV and extreme temperature tolerance
- Medium modulus, neutral cure
- Supports glass and panel materials under high wind loads
- Excellent adhesion to multiple building materials
Applications:
- Structural and non-structural glass installation
- Structural fixing of panel systems
- Weatherproof sealing of various building materials
Why we recommend it:
For applications requiring structural load-bearing capability, Dowsil 795 is the ideal choice, particularly suited to curtain wall systems on Hong Kong's high-rise buildings.
Dowsil 995 Silicone Structural Sealant
Product features:
- Specifically formulated for structural glazing
- Excellent primerless adhesion
- +/-50% movement capability
- Compliant with global structural glazing standards
Applications:
- Structural joints in small to medium buildings
- Safety glass sealing
- Hurricane or impact-rated windows and doors
Why we recommend it:
For projects demanding the highest structural performance, Dowsil 995 offers unmatched reliability and durability.
SPEC SpECseal Acrylic
Product features:
- Single-component acrylic sealant, easy to apply
- Suitable for indoor and outdoor use
- Ideal for static or low-movement joint sealing
- Good adhesion to porous materials including brick, concrete, wood, and masonry
- Paintable after curing for aesthetic finishing
Applications:
- Door and window frame internal joint sealing
- Crack filling between brick, stone, and timber
- Interior walls, skirting boards, and decorative gap filling
- Residential and commercial repair and renovation
Why we recommend it:
SpECseal Acrylic is the ideal choice for static joint sealing, offering excellent value and good adhesion. Its easy application and multi-substrate compatibility make it popular in both renovation and construction markets.
Sikasil Pool Swimming Pool Sealant
Product features:
- Specifically designed for swimming pools and permanently submerged areas
- Outstanding chlorine and pool chemical resistance
- +/-25% joint movement capability
- Excellent anti-fungal performance
Applications:
- Swimming pool internal and external joint sealing
- Permanently submerged and wet areas
- Sports facility shower rooms and wet environments
- Sealing between tile, concrete, glass, and metal surfaces
Why we recommend it:
Sikasil Pool is the only sealant specifically developed for pool environments, providing effective resistance to chlorine corrosion - essential for Hong Kong's many residential and clubhouse pool projects.
SikaHyflex-305 AP Exterior Wall Sealant
Product features:
- Low modulus elastic sealant
- +/-50% high movement capability
- Excellent weather resistance and long-term durability
- Solvent-free, no corrosion risk
Applications:
- Exterior wall expansion joints and movement joints
- Window and door perimeter sealing
- Precast panel joint sealing
Why we recommend it:
SikaHyflex-305 AP excels at accommodating large building movements, making it ideal for Hong Kong's exterior wall sealing needs where thermal cycling creates significant joint movement.
Choosing by Application
General weatherproofing:
- Recommended: Dowsil 791
- Features: All-purpose, excellent weather resistance
Exterior walls:
- Recommended: SikaHyflex-305 AP
- Features: High movement capability, durable
Swimming pools:
- Recommended: Sikasil Pool
- Features: Chlorine resistant, anti-fungal
Structural glazing:
- Recommended: Dowsil 995
- Features: Structural-grade strength, international standards compliant
Choosing by Performance Need
High movement: Choose products with +/-50% movement capability such as Dowsil 791 or SikaHyflex-305 AP
Chemical resistance: Choose specialist products such as Sikasil Pool (chlorine resistant)
Structural strength: Choose structural-grade products such as Dowsil 995 or Dowsil 795
Budget-friendly: Choose Weber series products or SPEC SpECseal Acrylic
Application Tips
- Substrate preparation: Ensure surfaces are clean, dry, and free of oil and contaminants.
- Temperature conditions: Avoid application in extreme temperatures.
- Curing time: Allow adequate curing time based on product specifications.
- Safety precautions: Maintain ventilation and avoid direct skin contact.
Conclusion
Selecting the right sealant product is crucial for ensuring project quality. In Hong Kong's climate, prioritise neutral cure sealants with excellent weather resistance and anti-ageing properties. For specialist applications such as swimming pools and curtain walls, use purpose-developed products for optimal results.
Regardless of product choice, always purchase from reputable suppliers and follow product instructions strictly to achieve the expected performance and service life.
791 vs 793 vs 795 Sealant Comparison
Dowsil (formerly Dow Corning) 791, 793, and 795 are the three most commonly used sealant series in Hong Kong's construction industry, but each serves a different purpose:
| Model | Full Name | Type | Primary Use | Movement |
|---|---|---|---|---|
| Dowsil 791 | Weatherproofing Sealant | Neutral silicone | Exterior wall joints, curtain wall weatherproofing, general sealing | +/-25% |
| Dowsil 793 | Silicone Glazing Sealant | Neutral silicone | Glass glazing, window frame sealing | +/-25% |
| Dowsil 795 | Structural Glazing Sealant | Neutral silicone (structural) | Structural curtain wall glazing, wind load bearing | +/-12.5% |
Quick guide: 791 is for general weatherproof sealing (most versatile), 793 is specifically for glass glazing installation, and 795 is for curtain wall projects requiring structural bonding (highest strength but lower flexibility). If unsure which to use, 791 is the safest all-purpose choice.
Is 791 Sealant Waterproof?
Dowsil 791 offers excellent waterproofing performance and is one of the most widely used waterproof sealants in Hong Kong's construction industry. Its waterproofing properties include:
- Forms an elastic waterproof seal after curing, providing long-term moisture barrier
- Outstanding weather resistance capable of withstanding Hong Kong's intense UV, heavy rain, and typhoon conditions
- +/-25% movement capability to accommodate thermal expansion and contraction in building structures
- Suitable for both indoor and outdoor use, including bathrooms, window frames, and exterior wall joints
Note: 791 is a sealant designed for filling joints and expansion gaps. For tile joint waterproofing, use tile grout rather than silicone sealant.
