Silicone sealants for glass curtain walls
Structural and weatherproofing silicone sealants are key materials that hold curtain wall glass panels firmly to aluminum frames while sealing joints to keep rain and wind from entering the building.
Glass curtain walls are a familiar sight on office towers, hotels and shopping centers. Behind that seamless appearance are two types of silicone sealant with completely different roles, which are often confused when purchasing.
Structural vs. weatherproofing sealants
| Criterion | Structural silicone sealant | Weatherproofing silicone sealant |
|---|---|---|
| Function | Carries wind load, holds glass to the frame | Seals joints between glass panels |
| Location | Between the glass edge and the aluminum frame | Outermost joint directly exposed to the weather |
| Design tensile strength | Approx. 0.14 MPa per standard | Not used for load bearing |
| Movement capability | Lower | From ±25% to ±50% |
| Common form | One- or two-component | One-component |
Using weatherproofing sealant in place of structural sealant is a dangerous mistake, because the material is not designed or tested to hold glass panels under storm wind loads.
Technical requirements for application
Structural sealant joint dimensions are calculated based on the design wind pressure and glass panel size. The minimum bite width is typically 6 mm or more, with a width-to-depth ratio between 1:1 and 3:1.
- Clean glass and aluminum using the two-cloth method with the recommended solvent.
- Use a primer if adhesion test results on the actual substrates are not satisfactory.
- Apply structural sealant in a shop with dust and temperature control.
- Keep a log of sealant lot numbers, application dates and peel test results.
Compatibility and adhesion testing
Before application, contractors should send samples of glass, aluminum frames, spacer tapes and gaskets to the sealant manufacturer's laboratory for compatibility testing. Some spacer materials can cause the sealant to discolor or lose adhesion over time.
Curtain wall maintenance
Every few years, building management should inspect weatherproofing joints for cracks, edge debonding or discoloration. Replacing the outer joint sealant in time helps protect the structural sealant inside.
As-built records should document the sealant type, lot numbers and detailed joint drawings for each area. When broken glass needs replacing or local repairs are required, the maintenance team can then select a material compatible with the existing sealant, avoiding new sealant failing to adhere to the old.
Contact AMS Vietnam for advice on selecting structural and weatherproofing silicone sealants for your curtain wall project.
