Bostik N49 Primer

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The Bostik N49 Primer is a clear, one-part primer designed to enhance the adhesion of Bostik polyurethane sealants on porous substrates. It ensures a strong bond, particularly in water-immersed applications. Ideal for use with Bostik Seal N Flex® 1, Bostik Seal N Flex® FC, Bostik Construction PU, and Bostik Fireban® One on porous surfaces like concrete, render, brick, blockwork, lightweight blocks, and unglazed ceramic tiles.


  • Promotes high bond strength of polyurethane sealants on porous substrates
  • Clear appearance for neat application
  • One part - no mixing required for ease of use


  • Colour: Clear
  • Appearance: Thin, colourless liquid
  • Coverage: 1 liter covers approx. 50 lineal meters of joint per liter
  • Drying Time: 15 minutes
  • Composition: Moisture sensitive


Prior to applying Bostik N49 Primer, ensure the substrate is sound, dry, clean, and free from any dust, residue, or contamination. Follow the substrate preparation guidelines detailed in the applicable Polyurethane Sealant Technical Data Sheet.


Bostik N49 Primer is formulated for use on porous substrates such as concrete, render, and masonry. Apply it with a soft brush and allow a minimum drying time of 15 minutes before applying the sealant. Please note that this primer is not suitable for non-porous substrates like hard plastics and ferrous or non-ferrous metals.

To maximize adhesion results:

  1. Decant the required quantity that can be applied by brush within 30 minutes into a clean, dry container.
  2. Primer that changes colour or becomes thicker has commenced to cure and should be discarded.
  3. Avoid dipping the same brush into the original container unless the entire contents are applied in 30 minutes.
  4. Use a clean, dry container on each decant to avoid contamination and shortened pot life.
  5. Discard any unused primer; do not pour any unused primer back into any remaining original primer in the original container.

Sealant must be applied within 4 hours, or re-priming is required. A sample test application is recommended on all substrates as staining may occur where the primer has been applied to areas not covered by polyurethane sealant.

Primer Yield Guide:

1 liter of primer will coat approximately 50 lineal meters of concrete joint interface, depending on wastage and substrate type.


Store the primer between 5°C and 30°C. Shelf life is twelve months in the original unopened container.

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Bostik N49 Primer

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