Selleys Butyl Mastic is a synthetic resin, butyl rubber based mastic which forms a smooth tough skin, but remains permanently plastic underneath. It is available Off White.

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: –35° to +65°C
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 mineral turps or white spirits

Where can this product be used?
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.
Ideal for dust proofing cars, trucks, caravans, boats, etc. and is suitable for sealing cracks and gaps around brickwork, roofing and cladding. 

What materials is this product suitable for?
Please contact your store to confirm avaliability, as some stores may have a limited range.

The following should only be used as a guide and the installer should apply all Australian Standards, BCA/NZBC requirements, and best practices when installing.

Surfaces to be sealed must be clean, dry and free from dust, grease, old mastic and  flaking paint. If necessary clean with degreasing solvent such as white spirits.
Cut nozzle supplied at an angle and to the required opening. Cut end off nipple on cartridge, fit nozzle and insert in suitable caulking gun such as the Selleys Light Speed caulking gun.
If sealing lap joints, apply suitable size bead of Butyl Mastic to one surface through the intended fasten line. Bring surfaces together squeezing the mastic bead out on both surfaces and mechanically fix join where necessary.
If sealing open joints, apply Butyl Mastic by forcing it into the joint ahead of the nozzle. This method aids in properly filling the joint and forcing mastic to wet on to the sides of the joint. If required, smooth surface with spatula dipped into mineral turps.


Not an elastomeric compound, it should not be used in joints subject to considerable dynamic movement.
Should not be used where joint movement will exceed ±8%.
Maximum service is achieved when used within joints; it is not recommended to be used as a "skim" coating over joints.
Not recommended for use in joints required to resist static air or water pressure. 

Surfaces must be clean and dry.
Life expectancy in joints is approximately 5 years
Interior applications may have greatly extended skin over time due to the reduced presence of sunlight.
Allow surface to skin before painting, i.e. approximately 24 hours after application.
Butyl Mastic can be painted over using oil or water based paints after the surface has skinned.


SKU 9300697101495
Barcode # 9300697101495
Brand Selleys
Shipping Weight 0.5000kg
Shipping Width 0.100m
Shipping Height 0.100m
Shipping Length 0.100m
Shipping Cubic 0.001000000m3

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