Repair Systems — 03 — Facade & External Envelope
Neutral cure silicone sealant systems
Technical product reference for neutral cure silicone sealant systems used in facade glazing perimeter sealing, aluminium window frame weathersealing and UV-exposed facade joint remediation on Australian Class 2 strata buildings. Covers product classification, system selection, substrate compatibility and brand comparisons.
What are neutral cure silicone sealant systems?
Neutral cure silicone sealants are one-part, moisture-curing silicone sealants that release neutral by-products (typically oxime, alkoxy or acetamide) on cure — in contrast to acetic cure silicone which releases acetic acid (vinegar). This distinction is critical in facade remediation: acetic cure silicone attacks aluminium, galvanised steel and many metals, while neutral cure silicone is safe on these substrates. All silicone sealants specified for facade use involving metal frames must be neutral cure.
Product Reference
3 products — 3 brands — neutral cure silicone weatherseal systems — scroll to view all
Dow 791 Silicone Weatherseal
One-part neutral cure silicone — weatherseal / facade perimeter
System Description
Dow 791 Silicone Weatherseal is one of the most widely used silicone sealants in Australian facade remediation and new construction. It is a one-part, neutral cure silicone sealant designed for perimeter sealing around aluminium window and door frames, curtain wall systems, glazing unit perimeters and facade panel joints where UV resistance and long-term weathering performance are critical. Unlike acetic cure silicone, Dow 791 does not release acetic acid on cure and is safe to apply against metals including aluminium, galvanised steel and stainless steel. It bonds to glass, anodised and powder-coated aluminium, most plastics and cleaned masonry. Primer is generally not required on most substrates but a Dow primer (Dow 1200 OS or equivalent) may improve adhesion on some difficult substrates — confirm with Dow technical. Dow 791 is not paintable — where the sealant joint must be overpainted, a polyurethane sealant is required instead.
Technical Properties
- Neutral cure — no acetic acid release — safe on metals, aluminium and galvanised substrates
- UV-stable — retains elasticity and colour in Australian outdoor conditions
- Excellent adhesion to glass, anodised aluminium, powder-coated aluminium and most facade substrates
Limitations
- Not paintable — do not specify where sealant joint will be overpainted (specify polyurethane sealant instead)
- Not suitable for structural glazing bonding — Dow 983 or similar structural silicone required for structural glass-to-frame bonding
- Not suitable for immersed joints (pool or tank) without confirming suitability from TDS
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 silicone sealant designed for facade weathersealing, window and door frame perimeter sealing and glazing perimeter sealing applications. As a neutral cure product, it does not release acetic acid on cure and is suitable for application against metals including aluminium. It offers UV resistance and long-term outdoor weathering performance suitable for Australian climate conditions. Primer (Sika Primer-3N or Sika Primer-215) may be required on some substrates — confirm from Sika TDS. Sika SikaSil products are distributed through Sika Australia's national network with local technical support. SikaSil-WS 305 CT is not paintable. TODO: owner confirm — confirm current Australian product designation, movement class, primer requirements and substrate compatibility with Sika Australia technical.
Technical Properties
- One-part neutral cure — no acetic acid — safe on metals and aluminium
- UV-resistant — suitable for exposed Australian facade and weatherseal applications
- Suitable for aluminium frame perimeter sealing and glazing perimeters
Limitations
- Not paintable — specify PU sealant where sealant will be overpainted
- Not suitable for structural glazing bonding without structural silicone designation
- Primer may be required on difficult or contaminated substrates
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Tremco Spectrem 1
One-part neutral cure silicone — curtain wall / facade weatherseal
System Description
Tremco Spectrem 1 is a one-part neutral cure silicone sealant used in facade and curtain wall weatherseal applications. It is suitable for perimeter sealing around aluminium window and door frames, glazing unit perimeters and panel joints in commercial and residential facades. As a neutral cure product it is safe on aluminium, glass and most metals. Tremco Spectrem products are widely used in Australian facade remediation and curtain wall work and are supported by Tremco Australia's technical network. Primer (Tremco 636 or equivalent system primer) may be required on some substrates — confirm with Tremco Australia technical. Spectrem 1 is not paintable. TODO: owner confirm — confirm current Australian product designation, movement class, primer requirements and coastal suitability with Tremco Australia.
Technical Properties
- One-part neutral cure — no acetic acid release — suitable for aluminium and metals
- UV-stable — suitable for Australian outdoor and coastal facade exposure
- Suitable for curtain wall weatherseal and aluminium frame perimeter sealing
Limitations
- Not paintable — sealant remains exposed once cured
- Primer may be required on some substrates — confirm with Tremco technical
- Do not apply over existing cured silicone — removal of old sealant required
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of neutral cure silicone weatherseal 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 | Dow | Neutral cure | No | Yes | High — confirm TDS | Aluminium frame perimeter sealing, glazing perimeters, curtain wall weatherseal |
| SikaSil-WS 305 CT | Sika | Neutral cure | No | Yes | Confirm TDS | Facade panel joints, aluminium frame perimeter sealing, glazing perimeters |
| Spectrem 1 | Tremco | Neutral cure | No | Yes | Confirm TDS | Curtain wall weatherseal, facade panel perimeter sealing, aluminium frames |
Do not confuse neutral cure silicone with:
- Acetic cure silicone (releases acetic acid on cure — vinegar smell — attacks aluminium, galvanised steel and most metals — NOT suitable for facade joints or aluminium frames)
- Structural silicone sealant (specialist glazing product engineered for structural glass bonding — different formulation, application and inspection requirements — not for general facade joint use)
- Polyurethane sealant (different chemistry — PU is paintable, which silicone is not — PU is preferred where sealant joint will be overpainted — listed on the PU sealant pages)
- Polysulfide sealant (different chemistry — polysulfide is used in immersed and chemical-resistance applications — listed on the polysulfide sealant page)
- Butyl tape / preformed tape sealant (solid butyl rubber tape — different application — used as backing seal in some window systems, not as a facade joint sealant)
Disclaimer
This page provides general technical information only. Final product selection must be confirmed against the current manufacturer technical data sheet, project specification, substrate condition, exposure classification and applicator warranty conditions. Products marked TODO: owner confirm require verification before specifying. Do not rely on this reference as a substitute for professional engineering or facade consultant advice.