Sikasil® WS-305 S can be used for weatherproofing sealing applications where durability under severe conditions is required. (TDS p.1)
- Pack
- INFORMATION Unipack 600 ml
Step-by-step solution
Glazing, curtain walls and shopfronts
Weather-sealing joints in glass curtain walls, windows, shopfronts and metal cladding, and the specialist silicones used in structural glazing and insulating glass. This is professional facade work and needs project-specific adhesion tests.
- 6 steps
- 8 products
- 4 answers
You need this when…
- Water leaking at curtain-wall panel joints or corners
- Weather seal split, chalky or debonded from glass or aluminium
- Air whistling through shopfront glazing joints
- New curtain-wall or glazing package to be specified
The work, step by step
General guidance based on the manufacturer data sheets. Site conditions differ: confirm the system with MCT before you start. Where we do not name a product, ask us and we will confirm the right one.
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Step 1: Design, approvals and adhesion tests
Tests with the actual substrates and conditions must be done to confirm adhesion and compatibility (Sikasil WS-305 S p.1). All gaskets, tapes, setting blocks and sealants in contact must be approved by Sika in advance. Structural glazing use needs a detailed review of the project (Sikasil WS-305 S p.2). Structural glazing also needs a facade engineer's design.
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Step 2: Weather seal for glazing and curtain walls
Sikasil WS-305 S is a neutral-curing silicone weather seal for structural glazing, curtain walling and windows, with ±50 % movement. It is for experienced professionals only (Sikasil WS-305 S p.1). Sikasil WS-305 EU is the CE-marked equivalent, with the same use and the same professional-only note (Sikasil WS-305 EU p.1).
Sikasil WS-305 S Sika Professionals only Request a quotation Sikasil WS-305 EU Sika Professionals only Request a quotation Sikasil® WS-305 EU can be used for weatherproofing and sealing applications where durability under severe conditions is required. (TDS p.1)
- Pack
- INFORMATION Cartridge Unipack 300 ml 400 ml 600 ml
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Step 3: Get the joint shape right
The joint must be at least 6 mm deep, with a width-to-depth ratio between 2:1 and 4:1. Avoid joints deeper than 15 mm. Use a closed-cell foam backer rod, or polyethylene tape as a bond breaker in shallow joints. The ideal application temperature is 15–25 °C (Sikasil WS-305 S p.2).
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Step 4: Metal cladding, panels and shopfronts
Sikasil-715 WS is for curtain-wall and metal-cladding facades, with ±50 % movement, in joints 6–45 mm wide and 6–15 mm deep (Sikasil-715 WS p.1, p.2). SikaHyflex-305 EU is also listed for curtain walls and metal cladding (SikaHyflex-305 EU p.1). Sikasil-712 WS suits shopfronts and glass partitions (Sikasil-712 WS p.1). Pre-treat glass and anodised aluminium with Sika Aktivator-205, Aktivator-100 or Cleaner P (Sikasil-715 WS p.3).
Sikasil-715 WS Sika Sikasil®-715 WS is designed for weather proofing and sealing applications where durability under severe conditions is required. (TDS p.1)
- Temperature stated in TDS
- +5 °C to +40 °C (TDS p.2)
- Pack
- 300 ml cartridge, 12 cartridges per box
SikaHyflex-305 EU Sika SikaHyflex®-305 EU is designed for weather proofing and sealing applications where durability under severe conditions is required. (TDS p.1)
- Temperature stated in TDS
- +5 °C to +40 °C (TDS p.2)
- Pack
- 300 ml catridge, 25 cartridges per box
Sikasil-712 WS Sika Sikasil®-712 WS is designed for weather proofing and sealing applications where the sealants appearance is of importance (translucent/metallic look). (TDS p.1)
- Temperature stated in TDS
- +5°C to +40°C (TDS p.2)
- Pack
- 300 ml cartridge, 12 cartridges per box
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Step 5: Structural glazing and insulating glass (factory work)
Sikasil SG-500 CN is a two-part structural silicone adhesive for structural glazing, for experienced professionals only (Sikasil SG-500 CN p.1). Sikasil IG-25 is the secondary edge seal and SikaGlaze IG-5 PIB the primary seal for insulating-glass units, both for professional users (Sikasil IG-25 p.1; SikaGlaze IG-5 PIB p.1).
Sikasil SG-500 CN Sika Professionals only Request a quotation Sikasil® SG-500 CN is ideal for structural glazing and similar high-demanding industrial applications. (TDS p.1)
Sikasil IG-25 Sika Professionals only Request a quotation Sikasil® IG-25 is ideal as a secondary edge seal for insulating glass in structural glazing applications. (TDS p.1)
SikaGlaze IG-5 PIB Sika Professionals only Request a quotation SikaGlaze IG-5 PIB is used as primary seal in the production of dual-seal insulating glass units. (TDS p.1)
- Pack
- Cardboard cylinder 7 kg (Ø 190 mm)
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Step 6: Tool and finish
Tool within the skin time, pressing the sealant onto the joint sides. Use no tooling agents (Sikasil WS-305 S p.2). Silicone weather seals cannot be over-painted (Sikasil WS-305 S p.2).
Proposal brief
Glazing, curtain walls and shopfronts: scope and system
A starting point for a site proposal. Quantities, prices and the final specification follow a site visit or photos.
Scope of work
- Joint survey and adhesion tests on the project substrates
- Removal of failed weather seal over x running metres
- Cleaning, pre-treatment, backer rod and silicone weather sealing
- Water test of resealed areas
System build-up
| Step | Product | Pack | Source |
|---|---|---|---|
| 2. Weather seal for glazing and curtain walls | Sikasil WS-305 S (professionals) | INFORMATION Unipack 600 ml | TDS p.1 |
| 2. Weather seal for glazing and curtain walls | Sikasil WS-305 EU (professionals) | INFORMATION Cartridge Unipack 300 ml 400 ml 600 ml | TDS p.1 |
| 4. Metal cladding, panels and shopfronts | Sikasil-715 WS | 300 ml cartridge, 12 cartridges per box | TDS p.1 · May 2025, Version 03.01 |
| 4. Metal cladding, panels and shopfronts | SikaHyflex-305 EU | 300 ml catridge, 25 cartridges per box | TDS p.1 · December 2022, Version 03.01 |
| 4. Metal cladding, panels and shopfronts | Sikasil-712 WS | 300 ml cartridge, 12 cartridges per box | TDS p.1 · May 2025, Version 02.01 |
| 5. Structural glazing and insulating glass (factory work) | Sikasil SG-500 CN (professionals) | — | TDS p.1 |
| 5. Structural glazing and insulating glass (factory work) | Sikasil IG-25 (professionals) | — | TDS p.1 |
| 5. Structural glazing and insulating glass (factory work) | SikaGlaze IG-5 PIB (professionals) | Cardboard cylinder 7 kg (Ø 190 mm) | TDS p.1 |
What we need from you
- Facade drawings or photos, and joint length (running metres)
- Glass, frame and cladding materials, with their coatings
- Typical joint width and depth
- Access method (BMU, rope access, scaffold)
- Is any glass structurally bonded?
Site conditions
- Adhesion and compatibility tests approved before full work (Sikasil WS-305 S p.1, p.2)
- Application by experienced professionals (Sikasil WS-305 S p.1)
Not included
- Structural glazing design and calculations (by a facade engineer)
- Glass or gasket replacement
- Access equipment, unless agreed
Questions customers ask
Can our maintenance staff reseal the curtain wall?
Sikasil WS-305 S is for experienced professional users only, with adhesion tests on the actual substrates (Sikasil WS-305 S p.1). Please use a trained facade applicator.
Can the silicone be painted?
No. Sikasil WS-305 S cannot be over-painted (Sikasil WS-305 S p.2).
Is structural glazing just a stronger sealant?
No. Sikasil SG-500 CN is a structural adhesive used only by experienced professionals after project tests (Sikasil SG-500 CN p.1). The joint must be designed by a facade engineer.
Our skylight is polycarbonate. Which sealant?
Do not use Sikasil WS-305 S or Sikasil-712 WS on polycarbonate (Sikasil WS-305 S p.2; Sikasil-712 WS p.3). Ask us: it depends on site conditions.
Steps and product facts are taken from the manufacturer data sheets (page cited). Products are named only where the data sheet confirms the use; quantities follow a site visit or photos. General guidance: check the data sheet or ask us before you start.