Repair Systems — 03 — Facade & External Envelope
Polyurethane sealant — two part
Technical product reference for two-part polyurethane sealant systems used in high-movement facade joint remediation on Australian Class 2 strata buildings. Covers product classification, system selection, mixing requirements, application parameters and brand comparisons for two-component PU sealant systems.
What are two-part polyurethane sealant systems?
Two-part polyurethane (PU) sealants consist of two separate components — typically a base (Part A) and a curative or activator (Part B) — that must be mixed together on site in the correct ratio before application. Unlike one-part PU sealants which cure by reaction with atmospheric moisture, two-part systems cure by a chemical reaction between the two components, making cure speed independent of humidity. This provides a more predictable cure, faster development of full mechanical properties, and generally higher movement accommodation than one-part equivalents.
Product Reference
3 products — 3 brands — two-part polyurethane facade sealant systems — scroll to view all
Sika Sikaflex-2CSL
Two-part self-leveling polyurethane sealant — horizontal joints
System Description
Sikaflex-2CSL is a two-part, self-leveling polyurethane joint sealant designed for horizontal movement joints, expansion joints and control joints in precast concrete facades, concrete decks and plaza areas. Unlike one-part PU sealants, it requires mixing of A and B components on site and has a defined pot life — careful batching and timing is essential. Two-part PU sealants generally offer higher movement accommodation than one-part systems, making them suitable for wide or highly active movement joints. Sikaflex-2CSL self-levels after application and is suitable for horizontal joint orientations where gravity allows the sealant to flow and self-smooth. Backer rod is required for joint depth control. Primer (Sika Primer-3N or substrate-specific Sika primer) is typically required on porous substrates — confirm with Sika Australia technical. TODO: owner confirm — confirm current Australian product designation, movement class, mixing ratio, pot life and primer requirements with Sika Australia technical.
Technical Properties
- Two-part — A+B mixed on site — defined pot life (confirm from current TDS)
- Self-leveling — suitable for horizontal joints — not suitable for vertical or overhead joints
- High movement accommodation — confirm movement class from current Sika TDS
Limitations
- Self-leveling — not suitable for vertical or overhead joint application
- Two-part mixing required — more complex site application than one-part systems
- Defined pot life — material must be applied within pot life window once mixed
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Tremco Dymeric 240 FC
Two-part polyurethane sealant — facade expansion joints
System Description
Tremco Dymeric 240 FC is a two-part, chemically curing polyurethane sealant designed for facade expansion joints, structural movement joints and wide-movement facade applications. As a two-part system, it requires careful mixing of A and B components on site and must be applied within the pot life window. Two-part PU sealants are typically specified for joints with higher movement demands than one-part systems can accommodate, or where faster cure and better low-temperature performance is required. Primer (Tremco 636 or Primer AP) may be required on porous or non-porous substrates — confirm primer selection and application with Tremco Australia technical. TODO: owner confirm — confirm current Australian product designation, movement class, mixing ratio, pot life, primer requirements and availability with Tremco Australia technical.
Technical Properties
- Two-part chemically curing — A+B mixed on site — faster cure than moisture-curing one-part systems
- High movement accommodation — confirm movement class from current Tremco TDS
- Suitable for vertical and horizontal facade joint orientations
Limitations
- Two-part — defined pot life — must be applied promptly after mixing
- More complex site application than one-part systems — trained applicator recommended
- Primer may be required on most substrates — do not skip primer without TDS confirmation
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Fosroc Expandite Plastijoint
Two-part polyurethane sealant — construction and facade joints
System Description
Fosroc Expandite Plastijoint is a two-part polyurethane joint sealant used in Australian construction and remediation for movement joints, expansion joints and construction joints in concrete facades, precast panels and masonry structures. Fosroc is a well-established Australian-market brand with a comprehensive technical support network. Two-part PU systems from Fosroc are commonly specified in commercial and strata remediation where a higher movement accommodation or chemically curing system is required. Confirm the current product range and system designation with Fosroc Australia technical, as product names and formulations may have been updated. Primer (Fosroc Nitobond EP or substrate-specific primer) is typically required — confirm with Fosroc technical. TODO: owner confirm — confirm current product designation, movement class, mixing ratio, pot life and primer requirements with Fosroc Australia.
Technical Properties
- Two-part — A+B mixed on site — chemically curing without dependence on atmospheric moisture
- Suitable for construction joints, expansion joints and facade movement joints
- Good adhesion to concrete and masonry — primer required on most substrates
Limitations
- Two-part — defined pot life — must be used within pot life window after mixing
- Primer required on most substrates — confirm with Fosroc Australia technical
- Not suitable for structural glazing bonding
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of two-part PU sealant systems. Confirm all product selections against the current manufacturer TDS before specifying.
| Product system | Brand | Components | Movement | Paintable | Primer | Primary use |
|---|---|---|---|---|---|---|
| Sikaflex-2CSL | Sika | Two | High — confirm TDS | Yes — confirm | Required — confirm substrate | Horizontal expansion joints, precast concrete facades, traffic deck joints |
| Dymeric 240 FC | Tremco | Two | High — confirm TDS | Yes — confirm | May be required — confirm | Facade expansion joints, structural movement joints — vertical and horizontal |
| Expandite Plastijoint | Fosroc | Two | Confirm TDS | Confirm TDS | Required — confirm substrate | Construction joints, expansion joints, facade movement joints in concrete structures |
Do not confuse two-part polyurethane sealant with:
- One-part polyurethane sealant (moisture-curing, no mixing required — lower movement accommodation, easier site application — listed on the one-part PU sealant page)
- Structural silicone sealant (silicone chemistry — used for structural glazing bonding — different application and substrate requirements)
- Polysulfide sealant (different chemistry — older technology — used in aviation fuel tanks and specialist immersed joint applications — listed on the polysulfide sealant page)
- Polyurethane foam / expansion foam (closed-cell spray foam — not a joint sealant — used for gap filling and insulation, not facade joint remediation)
- Two-part epoxy adhesive (rigid adhesive — no movement accommodation — not a 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.