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Sikaflex Construction AP+: A Technical Overview
Sikaflex Construction AP+ is a one-component, moisture-curing polyurethane joint sealant designed for long-term elasticity in movement and connection joints across concrete and masonry construction. It extrudes cleanly, tools easily, and cures bubble-free for consistent seals. With ±25% movement capability, non-sag performance up to 30 mm vertical joints, and strong adhesion to common construction substrates, it’s a reliable choice for facades, floors, pavements, decks, bridges, and building envelope junctions. Typical temperature service range is −40 °C to +70 °C, suiting Australian conditions from cooler regions to hot summers.
≈800%
Tensile strain at break
Core Features & Specifications
- Movement capability: ±25% (ASTM C 719) for reliable performance in dynamic joints.
- Non-sag on vertical/soffit joints up to 30 mm for clean lines and reduced rework.
- Bubble-free curing technology for uniform, durable elastomeric seals.
- Shore A hardness ~35; elastic recovery ~70% for balanced flexibility and resilience.
- Tear resistance ~6.0 N/mm; secant modulus ~0.30 N/mm² at 23 °C, 60% elongation.
- Service temperature −40 °C to +70 °C; density ~1.25 kg/L.
- VOC content ~41 g/L; available in Black, Concrete Grey, White; 600 ml foils (20/box).
- Suits closed-cell PE backing rod; typical bead coverage 1.3–7.5 lm per 600 ml (see table).
The Sikaflex Construction AP+ Advantage
- Consistent application: smooth extrusion and long tooling window simplify neat finishes.
- Built for movement: ±25% capability helps prevent cracking and call-backs on live structures.
- Reliable vertical performance: non-sag up to 30 mm helps hold profile on tall joints.
- Substrate versatility: adheres to common construction materials with straightforward prep.
- Works across climates: wide service temperature range for Australian conditions.
Proactive Troubleshooting
Scenario: Applying over dusty or weak substrate
Potential Outcome: Poor adhesion and edge failure leading to leaks and premature maintenance.
Best Practice: Mechanically clean (e.g., wire brush/grind), remove dust, and prime as specified (e.g., Primer-3 N for porous) before installing backing rod and sealant.
Scenario: Using on stone or bituminous/EPDM surfaces
Potential Outcome: Staining or incompatibility causing softening or loss of performance.
Best Practice: Avoid natural/reconstituted stone and bituminous/EPDM substrates. Select compatible substrates or contact technical support for a suitable system.
Applications in Practice: Trade Scenarios
For Builders (On-site Applicator): Facade movement joints
The Professional's Challenge
Maintaining elastic seals through thermal cycling and wind load without slump or edge failure, while keeping production moving.
The Adheseal Solution
Size joints to a 1:0.5 width:depth ratio (≥8 mm depth). Insert closed-cell PE rod, prime per substrate, then gun Sikaflex AP+ and tool firmly. The ±25% movement and non-sag up to 30 mm support clean, durable profiles.
Best Practice Note
Keep substrate ≥3 °C above dew point; avoid solvent-based tooling fluids; use the recommended tooling agent for a smooth finish.
For Precast Installers (On-site Applicator): Panel connection joints
The Professional's Challenge
Achieving reliable seals on precast and prefabricated junctions with variable surface profiles and tight installation windows.
The Adheseal Solution
Lightly abrade and clean metals; activate (Aktivator-205) and prime where required (e.g., Primer-3 N). Apply Sikaflex AP+ with full sidewall contact to avoid voids; tool promptly for uniform compression.
Best Practice Note
Mask joint arrises for crisp lines; remove tape within skin time to prevent tearing the surface.
Frequently Asked Questions
What joint sizes and ratios should I use for movement joints?
Use a 1:0.5 width:depth ratio for facades (minimum 8 mm depth). For floors, target approximately 1:0.8. Movement joint widths typically range from 8–40 mm. Always insert a closed-cell PE backing rod and size joints to accommodate ±25% movement.
Can Sikaflex Construction AP+ be used on stone or bituminous substrates?
No. Avoid natural/reconstituted stone (risk of staining) and bituminous/EPDM materials due to incompatibility. Select suitable substrates or seek technical guidance for an appropriate system.
Is it paintable and what about tooling agents?
It can be over-painted with most water-based systems after full cure; verify compatibility with trials. Use a compatible tooling agent (non-solvent) for finishing. Solvent-containing tooling fluids should be avoided.
Applications & Benefits
| Application / Use Case | Key Benefit | Primary Trades |
|---|---|---|
| Facade movement joints | ±25% movement with non-sag profile for clean, durable seals | Builders, Remedial |
| Precast & prefabricated connections | Strong adhesion to common building substrates; long tooling time | Precast Installers, Builders |
| Floor and wall construction joints | Elastic recovery and tear resistance support live loads | Builders |
| Pavements, decks, bridges | Resilient polyurethane elastomer for temperature swings | Civil, Builders |
| Windows and doors | Clean extrusion and tooling for neat perimeter seals | Builders, Glaziers |
Applying Sikaflex Construction AP+: Enhanced Protocols & Best Practices
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Surface Preparation
Ensure substrates are sound, dry, and free from dust, oil, grease, laitance, and loose coatings. Mechanically clean where necessary and repair damaged arrises.
Mechanical Cleaning
Wire brush, grind, or grit blast to remove weak layers. Vacuum to remove dust.
Priming
Prime per substrate: porous (Primer-3 N), selected metals (Aktivator-205 ± Primer-3 N), PVC (Primer-215). Avoid puddling.
Timing: Substrate temperature must be +5 °C to +40 °C and at least 3 °C above dew point.Pro Tip: Use masking tape for crisp lines and remove within the skin time. -
Backing & Sizing
Insert closed-cell polyethylene backing rod to regulate sealant depth and provide a bond-breaker.
Facade Joints
Target width:depth of 1:0.5 (≥8 mm depth; 8–40 mm width typical).
Floor Joints
Target width:depth ~1:0.8 with robust edge preparation.
Timing: Prime immediately before sealant where specified; respect activator waiting times.Pro Tip: Keep cartridges/foils between +5 °C and +40 °C for smooth extrusion. -
Application & Finishing
Cut nozzle to suit joint width. Gun sealant ensuring full sidewall contact and no air entrapment. Tool firmly for a dense surface.
Tooling
Use a compatible, non-solvent tooling agent; avoid solvent-containing fluids.
Cleanup
Clean equipment immediately after use; cured material requires mechanical removal.
Timing: Typical skin time ~120 min at 23 °C/50% RH; tooling window ~100 min; curing ~2 mm/24 h.Pro Tip: Remove masking within skin time to prevent edge tear; maintain joint temperature control in hot/cold conditions.
Limitations & Safety
Product Limitations
Not for natural, reconstituted, or cast stone (risk of staining via plasticiser migration).
Do not use on PE, PP, PTFE, certain plasticised synthetics; avoid bituminous, natural rubber, and EPDM substrates.
Not for swimming pools, under water pressure, or permanent immersion.
Avoid alcohol-containing products during cure; colour variation may occur under UV/heat/chemical exposure.
Safety & Handling Requirements
Personal Protective Equipment
Wear suitable gloves, eye protection, and protective clothing. Wash hands after handling. Follow SDS guidance.
Ventilation Requirements
Use in well-ventilated areas. Manage vapours in enclosed spaces; avoid inhalation of mists/fumes.
Fire & Handling Precautions
Keep away from ignition sources during use of cleaners/primers. Store unopened foils between +5 °C and +25 °C in dry conditions.
Emergency First Aid
Eyes:
Rinse cautiously with water for several minutes; remove contact lenses if present and easy to do.
Skin:
Wipe off excess; wash with soap and water. Do not use solvent on skin.
Inhaled:
Move to fresh air and rest. Seek medical attention if symptoms persist.
Swallowed:
Rinse mouth; do not induce vomiting. Seek medical attention.
Refer to the Safety Data Sheet for full guidance and seek medical advice for any serious exposure.
Sikaflex Construction AP+ Application Guide
Aluminium / Stainless / Galvanised / Glazed Tile
Surface Preparation
Lightly abrade with a fine pad, clean thoroughly, ensure dry and dust-free.
Primer Requirements
Activator required for critical adhesion
Apply activator with a clean cloth; allow the recommended waiting time prior to sealing.
Aktivator-205Brass / Bronze / Copper / Titanium-Zinc
Surface Preparation
Light abrasion and cleaning; surfaces must be sound, clean, and dry.
Primer Requirements
Primer required
Activate, allow waiting time, then prime by brush before sealing.
Aktivator-205 + Primer-3 NPVC
Surface Preparation
Clean, dry, free from release agents and contaminants.
Primer Requirements
Primer required
Prime by brush as directed; avoid puddling.
Primer-215Powder-Coated Metals
Surface Preparation
Clean and conduct preliminary adhesion trials due to coating variability.
Primer Requirements
Trial recommended
Verify adhesion with site trials; prime if required based on results.
—Concrete / Mortar / Brick / Cement Renders
Surface Preparation
Sound, clean, dry; remove laitance and weak material by mechanical means; repair arrises as needed; remove dust.
Primer Requirements
Primer required for critical applications
Brush apply primer; avoid excess and puddling at joint base.
Primer-3 N