When building elements move, the sealant must move with them. Facade panels expand, windows shift with thermal cycling, and precast joints flex under load. If your sealant can’t handle continuous, significant movement, you face premature failure and water ingress. Hi-Flex Construction provides the robust ±50% movement capability and lasting UV resistance these dynamic joints demand, maintaining integrity where standard sealants fall short.

Why this product exists

Hi-Flex Construction is engineered to meet the extreme demands of dynamic building elements. This high-performance MS Polymer sealant specialises in sealing critical building joints like window perimeters, facade panels, and expansion joints that experience constant movement. Formulated with a low modulus and exceptional elongation, it ensures the joint seal remains intact, waterproof, and durable against environmental stresses and building movement for the long term. It’s the specification fulfilment where standard sealants are simply not enough.

The numbers that matter

Understanding these performance metrics helps specify the right product for high-movement applications:

  • Movement Capability: ±50% (ASTM C719) means a 20mm joint can expand or contract by 10mm without rupturing or losing adhesion. This capacity is essential for applications where differential thermal expansion or structural movement is significant.
  • Elongation at Break: 1100% approx. (ASTM D412) provides a substantial safety margin. This extreme flexibility ensures the sealant can stretch far beyond its rated movement without failing, offering robust resilience in dynamic conditions.
  • Hardness Shore A: 25 approx. (ASTM D2240) indicates a low modulus sealant. This low hardness allows the sealant to remain soft and flexible, minimising stress on the bond line as the joint moves and preventing premature cohesive or adhesive failure.
  • Non-Staining (ASTM C510 & C1248) prevents discolouration or oil migration onto sensitive architectural surfaces like natural stone or precast concrete, preserving the aesthetic integrity of the building envelope.

What it's like to use

Applying Hi-Flex Construction is straightforward. Ensure surfaces are clean, dry, and free of contaminants. Primerless adhesion is often achievable on non-porous substrates. For critical, high-performance, or highly stressed joints, prepare porous surfaces with Everflex Supaprime Sealant Primer. For non-porous surfaces, use Adheseal 50A Surface Prep. Apply the sealant at temperatures between 5°C and 40°C, filling the joint completely to avoid air entrapment.

Tool the sealant immediately after application, within approximately 10 minutes, to achieve a smooth finish. The sealant forms a skin quickly and cures at a rate of approximately 3mm per 24 hours under standard conditions (25°C and 50% humidity). Use a compatible backer rod to control sealant depth and prevent three-sided adhesion, crucial for optimal movement performance. Clean wet tools and spills with Xylene. For skin, use Adheseal Hand Wipes.

Where this product excels

  • Fenestration and Glazing: Use for perimeter sealing of windows and curtain walls where significant thermal movement is expected. Its low modulus ensures the seal moves with the frame and glass, preventing stress build-up.
  • Facade Cladding: Ideal for sealing joints in modern facade panels and external wall cladding. It provides durable weather sealing that accommodates the continuous expansion and contraction of panel systems.
  • Precast and Tilt-up Construction: Specify for expansion joints in precast and tilt-up panels. Its ±50% movement capability handles the large-scale structural movement typical in these assemblies, ensuring long-term joint integrity.
  • Dissimilar Materials: Effectively seals mechanically fixed joints and materials with different thermal expansion coefficients, such as aluminium to concrete, without cracking or losing adhesion.

Choose this when

  • When joints require a high movement capability of ±50% to prevent premature failure.
  • When a low modulus sealant is necessary to minimise stress on bond lines in dynamic applications.
  • When long-term UV stability and resistance to weathering are non-negotiable for exterior exposures.
  • When sealing architectural elements where non-staining performance is crucial to maintain aesthetic quality.
  • When a paintable sealant is required, understanding that non-flexible paints may crack.

Don't use this when

  • Not for: Long-term water immersion or internal swimming pool applications, especially where high levels of chlorine are present.
  • Not for: Structural glazing applications; instead, refer to N-80 or N-60 glazing silicones.
  • Not for: Totally confined spaces, as the sealant requires atmospheric humidity to cure.
  • Not for: Direct contact with bituminous, natural rubber, or EPDM surfaces, or any material that might leach oils or plasticisers.
  • Not for: All stone types without prior stain testing. For marble or granite, conduct testing or consider S100.

Hi-Flex Construction complies with ASTM C920-CLASS 50, the standard specification for elastomeric joint sealants, specifically meeting the Class 50 movement rating. This certification validates its ±50% movement capability under test conditions. Additionally, it complies with ASTM C1248 for non-staining performance, providing assurance against discolouration on sensitive substrates.

Distinguishing Hi-Flex Construction from other MS Polymers

Hi-Flex Construction stands out within the MS Polymer range due to its specialist focus on extreme movement and high-performance building joints. While it is a low modulus sealant, its engineering priorities differ significantly from other products.

For applications primarily involving waterproofing membranes, bond breakers, or fillet joints, Adheseal Hi-Flex 50 Low-Modulus Waterproofing Membrane is a better fit. If your project requires an anti-pick sealant for structural bonding or XPS panels, redirect to Adheseal Hi-Flex 60 Anti-Pick Primer. For general, everyday low modulus MS Polymer sealing tasks where extreme movement is not the primary driver, Adheseal Hi-Flex LM Low-Modulus Hybrid Polymer Sealant provides an economical and effective choice. Hi-Flex Construction is specifically for the critical joints demanding proven ±50% movement and architectural non-staining performance.