Repair Systems — 03 — Facade & External Envelope
Joint Sealant Replacement Systems
Technical product reference for joint sealant replacement systems in facade cladding — neutral-cure silicone, polyurethane, and hybrid polymer sealants for movement joints between cladding panels and at perimeter junctions. All cladding joint sealants must be installed with a backer rod to prevent three-sided bond, which eliminates the sealant's capacity to accommodate movement.
What are joint sealant replacement systems?
Joint sealants are the most frequently replaced element in cladding maintenance — typically requiring replacement every 15–25 years depending on product class, exposure, and joint geometry. Correct selection of sealant chemistry, movement class, and substrate preparation determines whether the replacement will achieve its design life.
Product Reference
4 product systems — joint sealant replacement — scroll to view all
Sika Sikaflex 11FC+ Neutral-Cure Polyurethane Facade Sealant
Polyurethane facade joint sealant — Class 25LM — paintable
System Description
Sika 11FC+ is a 1-component polyurethane facade joint sealant with Class 25LM movement capacity (±25% of joint width) — the minimum class for facade movement joints per industry practice. Neutral-cure formulation is safe on all substrate types including natural stone, anodised aluminium, and polycarbonate — unlike acetoxy-cure silicone which releases acetic acid on cure and can corrode metals. The sealant is paintable after full cure (typically 7 days at 23°C) — important for facades where the sealant joint must match surrounding painted surfaces. UV-stable formulation with 20+ year outdoor service life. Backer rod is mandatory for all joints exceeding 10 mm depth.
Technical Properties
- Sealant type: 1-component polyurethane — neutral cure — no acetic acid release
- Movement class: ISO 11600 Class F/EX 25LM — ±25% of joint width
- Tack-free time: 40 min at 23°C — full cure: 7 days at 23°C
Limitations
- Must not be applied to wet or damp substrates — minimum 48 hr surface dryness required
- Joint width must be 6–50 mm — outside this range performance cannot be guaranteed
- Backer rod is mandatory for joints deeper than 10 mm — controls depth-to-width ratio
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Tremco Spectrem 2 Neutral-Cure Silicone — Structural Glazing and Facade
High-performance neutral-cure silicone — Class 25LM — structural glazing
System Description
Tremco Spectrem 2 is a premium 1-component neutral-cure silicone sealant with structural glazing certification — used for both facade joint sealing and structural glazing applications where a single product must satisfy both weatherproofing and structural load transfer requirements. The neutral-cure chemistry is non-corrosive to aluminium, stainless steel, and anodised surfaces. UV-stable silicone chemistry provides 25+ year outdoor service life without significant hardening or chalking. Commonly specified for curtain wall joints, aluminium panel junctions, and ACP panel replacements requiring structural sealant adhesion.
Technical Properties
- Sealant type: 1-component neutral-cure silicone — non-corrosive to all metal substrates
- Movement class: ISO 11600 Class F/EX 25LM — ±25% movement capacity
- Shore A hardness: 32 — elongation at break: > 400% — tensile strength: 0.9 MPa
Limitations
- Not paintable — silicone chemistry does not accept paint — specify polyurethane or MS polymer where painting required
- Substrate must be primed on porous surfaces — FC sheet, concrete, masonry — confirm primer with Tremco
- Cost premium over polyurethane sealants — justify against structural glazing or high-performance requirements
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Mapei Mapesil AC Anti-Mould Neutral Silicone — Coastal and Humid Facades
Anti-mould neutral-cure silicone — Class 20LM — coastal facade joints
System Description
Mapei Mapesil AC incorporates an anti-mould agent that prevents fungal growth on the sealant surface — a critical requirement in humid and coastal Australian environments where silicone joints on exposed facade elements can develop visible mould within 2–3 years of application. Neutral-cure formulation is compatible with all substrate types. The wide colour range (40+ colours) allows colour-matching to adjacent panel or paint finishes. Suitable for all facade joint applications up to Class F/EX 20LM movement capacity — not a structural sealant and not suitable for high-movement joints requiring Class 25LM.
Technical Properties
- Sealant type: 1-component neutral-cure silicone with anti-mould additive
- Movement class: ISO 11600 Class F/EX 20LM — ±20% of joint width
- Anti-mould: EN 846 method 9 tested — prevents fungal growth on sealant surface
Limitations
- Class 20LM — not suitable for high-movement structural or primary facade movement joints — use Class 25LM
- Anti-mould additive dissipates over time — eventually mould will grow on aged sealant surface
- Not paintable — silicone chemistry does not accept paint
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Sika MS Polymer Facade Sealant — Paintable Low-Movement Joints
MS polymer facade sealant — Class 12.5 — paintable — low movement
System Description
Modified silicone polymer (MS polymer) sealants combine the paintability of polyurethane with the UV stability of silicone — addressing the key limitation of each. Suitable for facade joints where the sealant surface must be painted to match adjacent surfaces. Isocyanate-free formulation produces no toxic vapours during application — safer for enclosed or poorly ventilated areas. The adhesion to most building substrates (FC, concrete, aluminium, timber, steel) without primer makes it versatile for remediation where substrate conditions vary. Class F/EX 12.5 — suitable for thermal movement joints but not for structural or primary facade movement joints requiring 25LM.
Technical Properties
- Sealant type: 1-component MS polymer (modified silicone) — isocyanate-free
- Movement class: ISO 11600 Class F/EX 12.5 — ±12.5% of joint width
- Paintable: within 24–48 hr of application before full cure — confirm paint compatibility
Limitations
- Class 12.5 only — not for high-movement structural or primary facade movement joints — use 25LM
- Must be painted before full cure — if painting is delayed, adhesion to paint is unreliable
- Slightly lower UV stability than silicone — colour shift possible on long-term exposed joints
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of joint sealant replacement systems. Confirm all product selections against the current manufacturer TDS before specifying.
| Product system | Brand | Type | Move. class | Paintable | Anti-mould | UV stability | Primary use |
|---|---|---|---|---|---|---|---|
| Sika 11FC+ Polyurethane | Sika Australia | 1-component polyurethane | Class 25LM | Yes — after cure | No | Good — 20+ years | Facade movement joints — paintable surface required |
| Tremco Spectrem 2 Silicone | Tremco / Bostik | 1-component neutral silicone | Class 25LM | No | No | Excellent — 25+ years | Structural glazing and facade seals |
| Mapei Mapesil AC Silicone | Mapei Australia | 1-component neutral silicone | Class 20LM | No | Yes | Excellent | Humid and coastal — anti-mould facade joints |
| Sika MS Polymer | Sika Australia | 1-component MS polymer | Class 12.5 | Yes — before cure | No | Good | Low-movement — paintable joints — versatile substrate |
Do not confuse external facade joint sealants with:
- Acrylic gap filler or paintable acrylic sealant — acrylic-based gap fillers are designed for internal or low-movement joinery applications; they have minimal movement capacity (typically under 7.5%) and are not suitable for external facade joints subject to thermal expansion, wind deflection, or building movement
- Bitumen or bituminous sealant — not UV stable; bitumen-based compounds degrade rapidly on exposed facade joints, become brittle and crack, and stain surrounding panels — not suitable for visible external joints in cladding systems
- Acetoxy-cure silicone (standard bathroom silicone) — releases acetic acid during curing which corrodes aluminium, copper, and galvanised substrates; facade sealants must be neutral-cure silicone or MS polymer — never acetoxy-cure against metal cladding
- Backer rod — a polyethylene or PE foam rod used to fill joint depth before sealant application; backer rod controls sealant depth and prevents three-sided adhesion; it is a sealant substrate preparation component, not a sealant in itself
Disclaimer
Information is general only. Joint sealant selection, joint geometry, and application method must be confirmed by a facade engineer. Adhesion to specific cladding substrates must be verified by peel adhesion test. Three-sided bond must be prevented by a correctly sized backer rod. Do not rely on this reference as a substitute for professional engineering advice.