Repair Systems — 03 — Facade & External Envelope
Perimeter sealant — polyurethane
Technical product reference for polyurethane perimeter sealant systems used in window and door frame remediation on Australian Class 2 strata buildings. Covers paintable PU sealant selection for masonry-to-frame perimeter joints — the preferred sealant type where the perimeter joint will be overpainted with facade coating.
What are polyurethane perimeter sealant systems?
Polyurethane (PU) sealants for window and door perimeter joints are one-part, moisture-curing elastomeric sealants that cure to a flexible, paintable joint. The key advantage of PU over silicone for window perimeter joints is paintability — once cured, PU sealant can be overpainted with facade paint, allowing the sealant profile to be concealed within the rendered or painted facade finish. Silicone cannot be painted, leaving the sealant bead visible in the finished facade.
Product Reference
3 products — 3 brands — polyurethane perimeter sealant systems — scroll to view all
Sika Sikaflex-11FC+
One-part PU sealant — paintable — window and door perimeter
System Description
Sikaflex-11FC+ is the most widely specified one-part polyurethane sealant for window and door perimeter joint remediation on Australian Class 2 strata buildings where the sealant will be overpainted with facade paint or coating. Unlike silicone sealants, Sikaflex-11FC+ can be painted over once cured, making it the preferred choice when the perimeter sealant profile must be concealed by facade paint rather than left exposed. It bonds well to concrete, masonry, render and aluminium without a primer on most clean, dry substrates. It accommodates ±25% joint movement and has proven UV stability in Australian exterior conditions. For window perimeter joints, apply a backer rod behind the sealant where the joint is deeper than 8mm to maintain correct sealant geometry.
Technical Properties
- Paintable after cure with most architectural paints — the primary advantage over silicone for perimeter joints
- One-part — no mixing required — ready to use from cartridge
- ±25% movement accommodation (ISO 11600 Class F-25LM)
Limitations
- Not suitable for glazing perimeter where sealant remains exposed to UV — specify neutral cure silicone instead
- Not suitable for permanently submerged joints
- Moisture-curing — do not apply on wet substrates or in rain
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
Tremco Vulkem 116 is a one-part moisture-curing polyurethane sealant used for building facade joints, perimeter sealing and window and door frame perimeter applications in Australian commercial and strata remediation. It is paintable once cured, making it suitable for window perimeter joints that will be overpainted with facade coating. Primer (Tremco 636 or equivalent) may be required on some porous substrates for optimal adhesion — confirm substrate-specific primer requirements with Tremco technical. Confirm current Australian product designation, primer requirements and movement class with Tremco Australia technical before specifying. TODO: owner confirm — confirm all application parameters, movement class and primer requirements with Tremco Australia.
Technical Properties
- One-part moisture-curing PU — no mixing required
- Paintable after cure — suitable for perimeter joints that will be overpainted
- Suitable for facade movement joints, expansion joints and window perimeter sealing
Limitations
- Primer may be required on some substrates — confirm with Tremco technical before applying
- Not suitable for permanently submerged applications
- Do not apply on wet or frozen substrates
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Bostik Seal N Flex FC
One-part PU sealant — paintable — facade and perimeter
System Description
Bostik Seal N Flex FC (or equivalent Bostik one-part polyurethane facade sealant — confirm current product code with Bostik Australia) is a one-part polyurethane sealant suitable for perimeter sealing around window and door frames in masonry and rendered facades where the sealant will be overpainted. It is paintable once cured and suitable for movement joints and perimeter joints in masonry, concrete and rendered substrates. Widely available through Bunnings and hardware trade channels in Australia. Confirm movement accommodation class, primer requirements and suitability for Class 2 strata window perimeter applications with Bostik Australia technical before specifying. TODO: owner confirm — confirm product code, movement class and full application requirements with Bostik Australia.
Technical Properties
- One-part — no mixing — ready to use
- Paintable after cure — suitable for window perimeter joints to be overpainted
- Suitable for masonry, concrete and render substrates
Limitations
- TODO: owner confirm — confirm movement accommodation class with Bostik Australia technical
- Not suitable for structural glazing
- Not suitable for permanently submerged applications
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of polyurethane perimeter sealant systems. Confirm all product selections against the current manufacturer TDS before specifying.
| Product system | Brand | Components | Paintable | Primer | Movement | Primary use |
|---|---|---|---|---|---|---|
| Sikaflex-11FC+ | Sika | One | Yes | Usually not required | ±25% | Window perimeter joints — paintable — the benchmark product for this application |
| Vulkem 116 | Tremco | One | Yes — confirm | May be required — confirm | High — confirm TDS | Window perimeter and facade movement joints — confirm AU availability |
| Seal N Flex FC | Bostik | One | Yes | Confirm TDS | Confirm TDS | Window perimeter and masonry joints — confirm product code with Bostik |
PU vs silicone for window perimeter sealant — selection guide:
- Specify polyurethane when: the perimeter joint will be overpainted with facade paint or coating (PU is paintable, silicone is not)
- Specify neutral cure silicone when: the sealant will remain exposed (UV-stable, non-paintable) and the frame is aluminium, glass or metal — silicone is superior for UV-exposed glazing perimeters
- Never use acetic cure silicone on aluminium, galvanised or metal frames — acetic cure releases acid that attacks metals
- PU sealant on aluminium frames — confirm primer requirement with the PU sealant manufacturer before applying on anodised or powder-coated aluminium
- Do not specify rigid cementitious mortar for perimeter joint sealing — perimeter joints must accommodate movement and remain flexible
Disclaimer
This page provides general technical information only. Final product selection must be confirmed against current manufacturer TDS, substrate condition and exposure classification. Do not rely on this reference as a substitute for professional advice.