Butyl Mastic


Butyl Mastic is a synthetic resin, butyl rubber based mastic which forms a smooth tough skin, but remains permanently plastic underneath. It is available in 3 colours – White (off-white colour), Black and Grey.


Having excellent adhesion to timber, glass, concrete, masonry, aluminium, steel and marble, this product is a versatile sealant for joint movement not exceeding ±8%.

Applications for Butyl Mastic include:

  • Sealing aluminium windows to masonry
  • Sealing joints between pre-cast concrete panels or porcelain enamelled panels
  • Sealing edges of all types of wallboards or wherever a permanent waterproof seal is required
  • Sealing lap joints between metal applications with the inclusion of fasteners
  • It is ideal for dustproofing cars, trucks, caravans, boats, etc. and is suitable for sealing cracks and gaps around brickwork, roofing, cladding, etc.

Product Range

Product Code: 9300697101457

  • Size & Pack Type: 400g cartridge
  • Color: Black

Product Code: 9300697101464

  • Size & Pack Type: 400g cartridge
  • Color: Grey

Product Code: 9300697101495

  • Size & Pack Type: 400g cartridge
  • Color: White (off-white colour)

Technical Features

  • Remains permanently plastic under a smooth tough skin
  • Versatile sealant with excellent adhesion to a variety of substrates without the necessity to prime
  • Will not bleed into porous surfaces
  • Non-sag in joints up to 12mm vertical joint
  • Wide service temperature: –35o to +65oC
  • Excellent weathering characteristics
  • Does not corrode metals
  • Good water resistance
  • Life expectancy is approximately 5 years in a thick joint. It is recommended to use silicone sealant in thinner joints
  • Easy smoothing and clean-up with Turps or White Spirits

Application Tips

  • Should not be used where joint movement will exceed ±8%. Interior applications may have greatly extended skin over time due to the reduced presence of sunlight. Surfaces must be clean and dry.

Technical Details and Performance

Indicative information only, not to be used for setting specifications.


Alkyd resin/Butyl rubber binder with extending fillers


Thick non – slump paste. Easily extruded from cartridges using a hand gun.

Indicative Viscosity

11,000 to 15,000 Poise @ 25oC

Storage Life

12 months stored in original unopened containers stored below 24oC

Clean Up

Mineral Turps or White Spirits are suitable for cleaning off spills and tools

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