Repair Systems — 03 — Facade & External Envelope
Perimeter sealant — neutral cure silicone
Technical product reference for neutral cure silicone perimeter sealant systems used in window and door frame remediation on Australian Class 2 strata buildings. Covers product selection for aluminium window frames, glazing perimeters and UV-exposed perimeter joints — the preferred sealant type for metal-to-masonry and glass interfaces.
What are neutral cure silicone perimeter sealant systems?
Neutral cure silicone sealants are one-part, moisture-curing elastomeric sealants that cure by releasing a neutral by-product (alcohol or oxime) rather than acetic acid. This makes them safe for use on aluminium, galvanised steel, glass and other metal substrates — a critical distinction from acetoxy (acetic cure) silicones which release acetic acid and corrode these materials. Neutral cure silicone is the standard specification for window and door frame perimeter sealing on Australian Class 2 strata buildings.
Product Reference
3 products — 3 brands — neutral cure silicone perimeter sealant systems — scroll to view all
Dow Corning 791 Silicone Weatherseal
Neutral cure silicone — window and facade perimeter
System Description
Dow Corning 791 Silicone Weatherseal is a one-part, neutral cure silicone sealant widely used in Australian commercial and strata building facade remediation for window and door perimeter sealing. It bonds to aluminium, glass, metal, most paints and most construction substrates without a primer, and provides excellent weathering and UV resistance. Dow 791 cures without releasing acetic acid (unlike acetoxy cure silicones), making it safe for use on aluminium frames, galvanised steel and anodised surfaces. It is not paintable once cured — where the perimeter joint must be painted over, specify a polyurethane sealant instead. Dow 791 remains flexible, UV-stable and weather-resistant for many years of service in Australian exterior conditions including coastal exposure.
Technical Properties
- Neutral cure — safe on aluminium, galvanised steel, glass and metal frames
- UV-stable — suitable for exposed facade perimeter joints without UV degradation
- Excellent adhesion to glass, aluminium, metal and most painted surfaces without primer
Limitations
- Not paintable — where joint must be overpainted, specify polyurethane sealant
- Silicone does not bond to cured silicone — all existing silicone must be fully removed before re-application
- Not suitable for natural stone (may cause staining — test first)
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
Sika SikaSil-WS 305 CT is a one-part neutral cure construction silicone suitable for facade weathersealing, window and door perimeter joints, curtain wall joints and metal cladding panel joints. It releases no acetic acid during cure, making it compatible with aluminium, galvanised steel and most metal frame systems. SikaSil-WS 305 CT bonds to glass, aluminium, metal frames and most construction substrates. It is UV-stable and weather-resistant for long-term exterior exposure. As with all silicone sealants, it is not paintable once cured. Confirm primer requirements on specific substrates and confirm current Australian product designation with Sika technical before specifying. TODO: owner confirm — confirm current product designation, movement class and primer requirements with Sika Australia technical.
Technical Properties
- Neutral cure — safe on aluminium, galvanised steel and metal substrates
- UV-stable — for exposed facade and window perimeter applications
- Bonds to glass, aluminium, metal, concrete and most construction substrates
Limitations
- Not paintable — specify polyurethane sealant where paint-over is required
- Silicone does not bond to cured silicone — all existing sealant must be removed first
- Primer may be required on some substrates — confirm with Sika technical
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
Tremco Spectrem 1 is a neutral cure silicone weatherseal used in Australian commercial and strata building facade weathersealing and window perimeter joint remediation. It cures without releasing acetic acid, making it suitable for aluminium window frames, metal cladding panels and glass perimeter sealing. Spectrem 1 bonds to glass, aluminium and most construction substrates and provides long-term UV and weather resistance in Australian exterior conditions. It is not paintable once cured. Confirm current Australian availability, primer requirements and movement class with Tremco Australia technical before specifying. TODO: owner confirm — confirm current product designation, Australian availability and full application parameters with Tremco Australia.
Technical Properties
- Neutral cure — suitable for aluminium, glass and metal substrates
- UV-stable — for exposed window and facade perimeter applications
- Used in commercial and strata facade weathersealing across Australia
Limitations
- Not paintable — specify PU sealant where paint-over is required
- Silicone does not bond to existing cured silicone — all old sealant must be removed first
- Primer may be required on some substrates — confirm with Tremco technical
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of neutral cure silicone perimeter sealant systems. Confirm all product selections against the current manufacturer TDS before specifying.
| Product system | Brand | Cure type | Paintable | Aluminium safe | Movement | Primary use |
|---|---|---|---|---|---|---|
| Dow 791 Silicone Weatherseal | Dow | Neutral | No | Yes | ±25% | Window perimeter, glazing, facade weatherseal — the benchmark product |
| SikaSil-WS 305 CT | Sika | Neutral | No | Yes | Confirm TDS | Facade weatherseal, curtain wall joints, window perimeter |
| Spectrem 1 | Tremco | Neutral | No | Yes | Confirm TDS | Facade weatherseal, window perimeter — confirm Australian availability |
Critical selection notes for window perimeter sealant:
- Never specify acetic cure silicone for window frames — acetic cure releases acetic acid which attacks aluminium, galvanised steel and most metals — always confirm neutral cure
- Neutral cure silicone is not paintable — where the perimeter joint will be overpainted with facade paint, specify polyurethane sealant instead (listed on the perimeter sealant — polyurethane page)
- Silicone does not bond to cured silicone — all existing silicone must be fully removed before replacement — do not apply new silicone over old
- Structural silicone sealant (for structural glazing bonding) is a different, specialist product — not for general perimeter sealing use
- Primer may be required on some substrates — confirm with manufacturer before application on difficult or contaminated surfaces
Disclaimer
This page provides general technical information only. Final product selection must be confirmed against current manufacturer TDS, substrate condition and exposure classification. Always specify neutral cure (not acetic cure) silicone for all metal frame applications.