Repair Systems — 06
Movement joint sealants — silicone and polyurethane
Technical product reference for silicone and polyurethane movement joint sealants used in Australian Class 2 strata and commercial building remediation. Covers product chemistry classification, ISO 11600 movement ratings, brand comparisons, joint design requirements and procurement sources.
What are movement joint sealants?
This category covers silicone and polyurethane movement joint sealants used in Australian Class 2 strata, commercial and façade remediation. Sealants seal joints between structural and non-structural elements — façade panels, window frames, expansion joints, control joints, and balcony edge and deck joints. Product selection must consider sealant chemistry (silicone vs PU), cure type (neutral vs acetoxy for silicone), movement capacity (ISO 11600 classification), substrate compatibility, primer requirement, joint design (width, depth, backing rod, bond breaker), UV exposure, and whether the sealant must be paintable after cure.
Do not confuse with:
- Expansion joint cover systems — proprietary mechanical cover plates for wide structural expansion joints — not sealant-based
- Polysulfide sealants — two-component systems with different chemistry — not silicone or PU
- Fire-rated intumescent joint sealants — passive fire protection products — not standard weatherseal sealants
- Epoxy joint fillers — rigid, non-moving joint compounds — not movement joint sealants
- Backing rod alone — bond breaker foam — not a sealant — must be used in conjunction with sealant, not instead of it
Product Reference
7 products — 4 brands — silicone and polyurethane movement joint sealants — scroll to view all
System Description
DOWSIL 795 (formerly Dow Corning 795) is a one-component neutral-cure structural silicone sealant used for structural glazing and high-performance weatherseal applications on curtain wall, window and façade systems. In Australian Class 2 and commercial building remediation it is specified for structural joint sealing where high movement capacity, UV resistance and adhesion to glass, metal, masonry and concrete are required. Joints must be designed with a backing rod, correct width-to-depth ratio and compatible surface primer where required. Confirm compatibility with substrate coatings and contact Dow technical before specifying over existing sealant.
Technical Properties
- Neutral-cure — does not release acetic acid — suitable for use on metals, stone, masonry and porous substrates
- High movement capacity — ±50% (ASTM C920 Class 50) — exceeds ISO 11600 Class 25 requirements
- Excellent UV and weathering resistance — does not chalk, crack or degrade under direct sun exposure
Limitations
- Not suitable for use over existing non-compatible sealant without full removal — adhesion will not be achieved over incompatible old sealant
- Substrate primers required on many substrates — confirm from Dow technical data sheet for each specific substrate
- Joint design must comply with manufacturer guide — minimum width and depth must be calculated from anticipated movement
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
DOWSIL 791 (formerly Dow Corning 791) is a one-component neutral-cure low-modulus silicone weatherproofing sealant for curtain wall façade, expansion joint and perimeter weatherseal applications. It is neutral cure — it does not release acetic acid — making it suitable for use on metals, concrete, masonry and porous substrates as well as glass and aluminium. Conforms to ISO 11600-F&G-25LM. Movement capability is ±50%. Confirm substrate compatibility and primer requirements from Dow technical data before specifying.
Technical Properties
- Neutral-cure — does not release acetic acid — suitable for metals, masonry, concrete and porous substrates
- ISO 11600-F&G-25LM — movement capability ±50% — exceeds ISO 11600 Class 25 requirements
- Low modulus — low stress on joint faces — suitable for curtain wall and façade weatherseal joints
Limitations
- Not a structural sealant — not rated for structural glazing under ASTM C1184 — use DOWSIL 795 for structural glazing applications
- Primer required on certain substrates — confirm from Dow TDS for each specific substrate before application
- Not paintable — silicone surface cannot be painted without special topcoat system
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
Tremco Spectrem 2 is a one-component neutral-cure medium-modulus silicone sealant suitable for 2-sided structural glazing, exterior façade, curtain wall and glazing joint applications on Class 2 and commercial buildings in Australia. Neutral-cure system — no acetic acid release — suitable for a wider substrate range including aluminium, glass, steel, painted metal, plastic, stone, concrete and masonry. UV and ozone resistant. Part of Tremco CPG's complete façade sealant system — warranted when used with compatible Tremco primers throughout. Confirm ASTM C920 and ISO 11600 classifications from current Tremco CPG APAC TDS before specifying.
Technical Properties
- Neutral-cure — no acetic acid release — suitable for aluminium, glass, steel, masonry, concrete and porous substrates
- Suitable for 2-sided structural glazing applications — confirm structural glazing warranty requirements with Tremco CPG
- UV and ozone resistant — suitable for direct external exposure in all Australian climate zones
Limitations
- Primer required on many substrates — confirm primer selection from Tremco TDS and application guide for each substrate
- System warranty requires use of Tremco-specified primers — do not substitute with other brand primers
- Tremco CPG distribution in Australia more limited than Sika or Dow — confirm local availability before specifying
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
Sika Sikaflex-11 FC Purform (formerly Sikaflex-11 FC+) is a fast-curing one-component pure polyurethane sealant and adhesive widely used in Australian construction and remediation for façade, balcony, wall and floor joints. Suitable for sealing joints in concrete, masonry, metal, wood and most plastics. Can be painted after full cure. Used extensively in Class 2 strata remediation for sealing non-structural movement joints, window perimeter sealing, balcony edge joints and general construction joint sealing. Application temperature range +5°C to +35°C. Confirm joint width, depth and movement expectations against manufacturer joint design guidance before specifying.
Technical Properties
- One-component PU — moisture cures — no mixing required — straightforward field application
- Dual-function sealant and adhesive — one product for sealing and bonding applications
- Paintable after full cure — suitable for colour-matched repair in visible locations
Limitations
- Not a structural sealant — do not specify for structural glazing — use Sika structural silicone for structural glazing applications
- Lower UV resistance than silicone — may discolour with prolonged direct sun exposure on some colours
- Primer required on certain substrates — confirm from Sika TDS per substrate combination before application
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
Sika Sikaflex PRO-3 Purform (formerly Sikaflex-PRO-3 WF) is a one-component pure polyurethane weatherproofing sealant for floor and civil engineering joint applications including façade, balcony, horizontal and vertical movement joint applications in Class 2 and commercial building remediation. The Australian TDS (July 2025, Version 04.01) is available at aus.sika.com. Confirm ISO 11600 classification, exact movement capacity and primer selection per substrate from the current Sika Australia TDS before specifying.
Technical Properties
- One-component pure PU — moisture cures — confirm ISO 11600 classification from current Sika Australia TDS
- Pure polyurethane formulation — Purform technology — confirm UV resistance claims from current Australian TDS
- Suitable for floor and civil engineering joints — confirm suitability for façade and balcony deck applications with Sika Australia
Limitations
- Primer required on many substrates — mandatory on smooth concrete, steel and dense surfaces — confirm from Sika TDS
- Moisture-curing PU — do not apply to wet or damp surfaces — substrate moisture content must meet Sika requirements
- Not a structural sealant — do not use in structural glazing applications
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
Mapei Mapeflex PU50 SL is a one-component moisture-curing low-modulus polyurethane sealant for movement and construction joints in Class 2 strata, commercial and industrial building applications in Australia. Classified ISO 11600 F-25-LM with movement up to 25% and a low modulus of elasticity (0.25 N/mm² at 100% elongation). Shore A hardness 22. Suitable for vertical and horizontal joint applications on concrete, masonry, wood, aluminium and most plastics. Used for sealing movement joints in balcony floors, façade joints, expansion joints between structural elements and control joints in concrete slabs. Paintable after full cure. Confirm primer requirements per substrate from Mapei TDS.
Technical Properties
- One-component PU — moisture cures — no site mixing — suitable for contractor application on remediation sites
- Suitable for horizontal and vertical joint orientations — versatile for construction and remediation joint sealing
- Paintable after full cure — suitable for colour-matched repairs in visible locations
Limitations
- Primer required on many substrates — confirm from Mapei TDS before application on smooth concrete, metal or dense surfaces
- Not a structural sealant — do not use in structural glazing applications
- Moisture-curing — do not apply to wet or damp substrates — allow adequate dry time before sealing
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
Tremco Dymonic FC is a single-component, fast-curing, moisture-cure polyurethane hybrid sealant specifically formulated for façade and window perimeter sealing applications on Class 2 and commercial buildings in Australia. High UV resistance. Paintable after cure. Used for control joints, perimeter caulking around windows and doors, and panel joint sealing. Note: Tremco Australia also offers Dymonic 100 (a separate product — medium-modulus non-sag polyurethane with +100%/-50% movement capacity). Confirm which Dymonic product is appropriate for the specific application with Tremco Australia before specifying.
Technical Properties
- One-component moisture-cure PU-hybrid — fast curing — suitable for façade and window perimeter joint sealing
- Paintable after cure — suitable for colour-matched façade joint repairs in visible locations
- High UV resistance — suitable for external façade exposure in Australian climate conditions
Limitations
- Primer required on most substrates — do not apply without primer on smooth concrete, metal or dense surfaces — confirm from Tremco TDS
- Not suitable for submerged or water-retaining structure joints — do not use in below-grade submerged conditions
- Confirm movement capacity against project specification — Dymonic FC and Dymonic 100 have different movement ratings
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Brand Equivalents
Silicone and PU movement joint sealant equivalents across brands active in Australian Class 2 and commercial building remediation. * Confirm exact product and classification with manufacturer before specifying.
| System type | Dow | Sika | Mapei | Tremco |
|---|---|---|---|---|
| Silicone neutral-cure — structural / high-movement | DOWSIL 795 | Sikasil structural* | — | Spectrem 2 |
| Silicone neutral-cure — low-modulus weatherseal / façade | DOWSIL 791 | Sikasil-GP* | — | — |
| PU 1C — general purpose sealant / adhesive | — | Sikaflex-11 FC Purform | Mapeflex PU50 SL* | — |
| PU 1C — weatherproofing façade / high movement | — | Sikaflex PRO-3 Purform | — | Dymonic FC / Dymonic 100* |
Critical — Joint Design and Backing Rod
- Backing rod is mandatory for all movement joint sealant applications — bond breaker tape or closed-cell polyethylene foam rod must be installed before sealant application to prevent three-sided adhesion
- Three-sided adhesion causes cohesive failure — if sealant bonds to the back of the joint as well as the two joint faces, the sealant cannot stretch without tearing
- Joint width must be designed from anticipated maximum movement — minimum 6 mm joint width; width must be at least 4× the movement for ISO 11600 Class 25 sealants
- Joint depth must be controlled — depth should be approximately half the joint width for elastomeric sealants — confirm with manufacturer TDS
- Do not apply sealant in temperatures below 5°C or above 40°C without confirming manufacturer's temperature application limits
Disclaimer
Information is general only. Product selection must be confirmed against project requirements, substrate condition, joint design, movement expectations, manufacturer technical data sheets, NCC requirements, and relevant Australian and international standards including ISO 11600. Do not rely on this reference as a substitute for professional engineering or façade consultant advice.