- Suitable For: Mastic asphalt, roofing felt, corrugated iron, cast iron, fibre cement, slates, lead, copper, zinc, concrete and timber
- Area of use: EXT
- Application Method: Steel Trowel / Putty Knife
- Volume: 1L, 2.5L, 5L
- Container Type: Tin
- Type: Bitumen
- Colour: Black
- Brand: SIKA
- Manufactuer: SIKA
Sika® Black Jack®-903 Bitumen Trowel Mastic is a fibre-reinforced, heavily-filled bituminous compound designed for trowel application, forming a durable surface skin while remaining soft beneath to accommodate moderate movement. It is suitable for sealing, waterproofing, filling and bonding on a wide range of materials, including mastic asphalt, roofing felt, corrugated iron, cast iron, fibre cement, slates, lead, copper, zinc, concrete and timber, making it ideal for repairing holes and defects in roofing and guttering systems. Fast-drying and compatible with all bituminous coatings, the product delivers long-lasting flexibility after application.
Key Points
– Fibre-reinforced, trowel-applied bitumen mastic that remains flexible beneath the surface.
– Suitable for sealing, waterproofing, bonding and filling holes in multiple roofing and construction materials.
– Fast-drying and fully compatible with all bituminous surface coatings.
– Ideal for repairing mastic asphalt, roofing felt, metal surfaces, guttering and general roofing defects
For more in our range of roofing and bitumen products, please click here.
For our full range of products from Sika, please click here. For more information on Sika and their products, you can visit their website here
Mainly used for:
– Waterproofing, stopping, bedding, bonding and sealing.
– Adheres to/fills holes in: mastic asphalt, roofing felt, corrugated iron, cast iron, fibre cement, slates, lead, copper, zinc, concrete and timber.
LIMITATIONS
Do not use in areas where subsequent solvent contact is likely, and avoid inhaling vapours in confined spaces. The product must not be applied to damp surfaces, and sufficient drying time should be allowed before overcoating. Only black bituminous coatings should be used over the mastic, as other paints may be affected by bleeding. The manufacturer cannot anticipate all possible uses; it is the user’s responsibility to determine suitability. For advice, contact the Technical Services Department.
ECOLOGY, HEALTH AND SAFETY
Users must consult the most recent Safety Data Sheets (SDS) before using the product. The SDS provides guidance on safe handling, storage, and disposal, and contains physical, ecological, toxicological, and other safety-related information.
APPLICATION INSTRUCTIONS
SUBSTRATE PREPARATION
All surfaces must be dry, stable, and thoroughly cleaned of dirt, dust, and grease. Any remaining moisture should be removed with a dry cloth. Loose felt should be adhered with Black Jack®-904 Roof Felt Adhesive. Metal surfaces must be wire-brushed to remove rust, and long-term protection may require a rust-inhibitive primer such as red lead or zinc phosphate. Loose or blistered paint and tar-based coatings should be removed. New galvanised surfaces must be roughened or treated with a proprietary etch primer. Surfaces affected by algae or fungi should be cleaned with Sika® Mouldbuster as directed. For cold weather application, store the material in a warm room overnight prior to use.
APPLICATION
Sika® Black Jack®-903 Bitumen Trowel Mastic is ready for use and should not be thinned. Apply with a steel trowel or putty knife.
CRACKS AND HOLES
Force the mastic into cracks and finish with a 25 mm band at 3 mm thickness along the crack. For larger cracks or holes, embed a closely woven glass fibre membrane overlapping the defect by 50 mm, allow to dry, and then apply a second coat covering the membrane completely.
CORRUGATED IRON / FIBRE CEMENT SHEETING
Tighten loose hook bolts and trowel around with mastic. Remove loose screws, re-bed them in mastic, and top seal with a smooth finish. For cracked sheets, clean, prime with Black Jack®-902 Bitumen & Flashing Primer, embed a glass fibre band in the mastic, allow to dry, then overcoat with Black Jack®-902 Primer and Black Jack®-901 Bitumen Paint. The same method applies for sealing side and end laps.
TILES
Point up butt edges of ridge tiles, fillets, and slates using Sika® Black Jack®-903 Bitumen Trowel Mastic.
LEAD AND ZINC
Apply mastic over cracks and pinholes, reinforcing with a woven glass membrane if needed, ensuring full embedment and coverage.
FELT
Re-adhere loose felt with Black Jack®-904 Roof Felt Adhesive, then apply Sika® Black Jack®-903 Bitumen Trowel Mastic and overcoat with Black Jack®-905 All Weather Roof Coating. Felt must be completely dry before applying the mastic.
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| Elementlength | |||||||
| up to 1,5 m | up to 2,5 m | up to 3,5 m | up to 4,5 m | up to 2,5 m | up to 3,5 m | up to 4,5 m | |
| Type of window frame material |
Minimum witdth of joints for a butled mounting b in mm | Minimum witdth of joints for a inner mounting b in mm | |||||
| Hard PVC (white) | 10 | 15 | 20 | 25 | 10 | 10 | 15 |
| Hard PVC and PMMA (dark) (colour extruded) | 15 | 20 | 25 | 30 | 10 | 15 | 20 |
| Hard PUR integral foam | 10 | 10 | 15 | 20 | 10 | 10 | 15 |
| Wood-aluminium-window | 10 | 10 | 15 | 20 | 10 | 10 | 15 |
| Aluminium-plastic sandwich frame (bright) | 10 | 10 | 15 | 20 | 10 | 10 | 15 |
| Aluminium-plastic sandwich frame (dark) | 10 | 15 | 20 | 25 | 10 | 10 | 15 |
| Wooden window frame | 10 | 10 | 10 | 10 | 10 | 10 | 10 |
From: £3.11 inc. VAT
£2.59 ex. VAT
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£6.98 ex. VAT
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