When the joint movement goes beyond the expected, demanding extreme flexibility and reliable sealing, Bostik Seal 'N' Flex One Plus P590 delivers. It’s engineered for the most dynamic expansion joints, providing +100%/-50% movement capability and bubble-free curing even on damp substrates. This ensures long-term integrity where standard sealants would fail, keeping large-scale construction joints sealed and stable.

Why this product exists

Bostik Seal 'N' Flex One Plus P590 is a next-generation Flex-IQ polyurethane sealant designed for extreme movement in construction joints. It provides a flexible, bubble-free seal that accommodates significant building dynamics, thermal expansion, and contraction. Formulated to perform on damp or moist substrates without compromising cure quality, it prevents common gassing issues found with conventional polyurethanes, making it ideal for critical expansion joints up to 80mm wide.

The numbers that matter

With a remarkable +100% / -50% joint movement capability, this sealant manages extreme expansion and compression cycles without compromise. This high movement rating is supported by an elongation at break of over 1000%, offering an immense safety margin against tearing and premature failure from thermal shock, settlement, or dynamic loads. A Shore A hardness of 20-25 ensures a balance of flexibility and durability, allowing the sealant to absorb movement while resisting wear in demanding environments.

What it's like to use

Bostik Seal 'N' Flex One Plus P590 is a non-sag, thixotropic paste, making it easy to tool and apply consistently. It cures via moisture, forming a bubble-free seal that is unaffected by the tooling method, even on damp or moist substrates. The sealant features a skin time of 90 minutes, providing ample working time for proper placement and finishing. Full cure typically takes 7 days on porous substrates, extending to over 14 days for joints wider than 20mm. For optimum adhesion on non-porous substrates like plastics and metals, prime with Bostik N40 Primer. For porous surfaces and periodically immersed applications, use Bostik N49 Primer. Uncured material and tools can be cleaned immediately after use with Bostik Handy Wipe towels.

Where this product excels

This sealant is engineered for demanding construction and facade applications:

  • Civil Construction: Sealing large expansion joints in in-situ concrete, precast, and tilt-up panels that experience significant structural movement and thermal cycling. Its bubble-free cure ensures joint integrity in humid conditions or on damp concrete.
  • Commercial Facades: Providing a robust, flexible seal for metal cladding, aluminium composite materials, and aluminium windows, accommodating high wind loads and facade movements. Compatibility testing (P.A.T.S.) is advised for coated panels to ensure adhesion.
  • Masonry: Sealing joints in brickwork and blockwork, where its extreme elasticity prevents cracking and water ingress caused by differential movement and thermal expansion.
  • Specialty Panel Systems: Adhering reliably to GRC, fibreglass, granite, sandstone, and marble panels, maintaining flexibility and preventing joint failure in complex architectural designs.

Choose this when

  • When sealing extreme movement joints with cyclic expansion and compression of +100%/-50%.
  • For projects requiring bubble-free curing, especially on damp or moist substrates.
  • Sealing large expansion joints up to 80mm wide in concrete, precast, or tilt-up panels.
  • When a highly elastic, UV-resistant, and paintable polyurethane sealant is required for outdoor exposures.

Don't use this when

  • Not for: Use in chlorinated water, such as swimming pools or spas, or constant saltwater immersion.
  • Not for: Glazing applications.
  • Not for: Trafficable joints where continuous vehicle or heavy foot traffic is expected.
  • Not for: Application on specific plastics including PE, PP, PC, PMMA, PTFE, soft plastics, neoprene, or bituminous substrates.
  • Not for: Cement-based substrates within 28 days of initial pour or set.
  • For standard movement joints within ±50% (consider Seal 'N' Flex One P390 for these applications).

Bostik Seal 'N' Flex One Plus P590 meets ASTM C920 and ISO 11600 standards for elastomeric joint sealants, confirming its performance in demanding construction environments. It also complies with EN 15651-1 F-EXT-INT-CC 25LM and EN 15651-4 PW-EXT-INT-CC 25LM, signifying suitability for external and internal use in facade and pedestrian applications. Furthermore, it holds AS/NZS 4020:2018 certification for potable water contact, making it suitable for applications where incidental contact with drinking water is a consideration, provided other product limitations are observed.