Sika Black Jack 903 Fibre Reinforced Bitumen Trowel Mastic 5L 90305

Product Details: Brand: Sika | Range: Black Jack | Product Type: Fibre Reinforced Bitumen Trowel Mastic | Size: 5 Litre | Colour: Black | Product Code: 90305 | Model: 90305 | SKU: 486991 | MPN: 852674 | Sika Code: 852674 | EAN: 5029347009359 | Barcode: 5029347009359

Sika Black Jack 903 Fibre Reinforced Bitumen Trowel Mastic 5L is a ready-to-use black bituminous repair compound for larger roof and exterior building repairs. It has a thick trowel-grade consistency, making it suitable for pressing into cracks, gaps, holes, seams and damaged areas where a brush-applied coating would not be enough.

The 5 litre tin is the largest size in this 903 range. It is the best choice when the job involves broader repair areas, repeated patching, several roof defects or trade maintenance work where smaller tins may run out too quickly.

Built For Larger Roof Repair Work

The 5L size is aimed at bigger or more demanding repair jobs. It gives more material for working across wider roof sections, multiple defects, gutter runs, flashing details and maintenance areas where a compact tin would not be practical.

• Larger roof cracks, holes, splits and patch repair areas.
• Repeated repairs across felt, asphalt, metal or compatible roof surfaces.
• Longer seams, laps, edges and roof detail repairs.
• Gutter, pipe, downpipe and roofline maintenance work.
• Flashing edges, chimney bases and roof penetration repairs.
• Trade or frequent use where 1L or 2.5L may not provide enough material.

Why Choose The 5L Tin

Choose the 5L tin when the repair job is beyond a small patch or a few isolated defects. It is better suited to planned maintenance, larger roof repair areas and repeated use across several sections of the same job.

For one small crack or a minor touch-in repair, the 1L size is usually enough. For several localised repair points, the 2.5L size may be the better middle option. For broader roof repair work, larger patching or trade maintenance, the 5L tin is the stronger choice.

Key Benefits

• Larger 5L Tin: Better suited to bigger repair jobs and frequent use.
• Fibre-Reinforced Compound: Helps strengthen bitumen repair areas.
• Trowel-Grade Texture: Can be pressed into cracks, gaps, holes and joints.
• Ready To Use: No mixing required before application.
• Black Bitumen Finish: Suitable for compatible black bitumen roof repairs.
• Good For Trade Maintenance: Useful where several roof areas need attention.
• Broad Surface Compatibility: Suitable for many clean, dry and prepared roofing or building surfaces.
• Flexible Repair Use: Designed to tolerate moderate movement after application.

Suitable Repair Areas

Sika Black Jack 903 can be used for patching, sealing, bedding, bonding and waterproofing on suitable prepared surfaces. It is commonly used around roofing felt, mastic asphalt, corrugated iron, cast iron, fibre cement, slates, lead, copper, zinc, concrete and timber.

• Larger roofing felt splits, holes and joint repairs.
• Mastic asphalt cracks, seams and damaged local areas.
• Corrugated iron and fibre cement roof sheet repairs.
• Lead, copper and zinc flashing details.
• Concrete and timber areas where the surface is suitable and prepared.
• Gutters, downpipes, pipe joints and roofline details.
• Chimney bases, roof penetrations and external waterproofing repair points.

How To Use On Larger Repair Areas

Always read the current Sika product data sheet and safety data sheet before use. With the 5L tin, it is worth preparing the full repair area before application so the mastic can be applied cleanly and consistently across each section.

• Assess the full job: Identify all cracks, holes, seams, roof edges, gutter joints and flashing details that need repair.
• Prepare the surface: Remove loose material, dust, dirt, rust, grease, flaking coating and unstable debris from each area.
• Check dryness: The surface should be dry, clean, sound and stable before the mastic is applied.
• Apply with the right tool: Use a steel trowel, spatula or putty knife to work the mastic into the repair area.
• Build a strong patch: Press the mastic into gaps, cracks, holes and seams, then spread beyond the damaged edge to help bridge the repair.
• Use reinforcement where needed: For larger holes, wider cracks or weaker zones, embed a suitable reinforcing membrane before applying a further layer.
• Allow the repair to settle: Let the mastic form its surface skin before further handling, coating or exposing the area to heavier use.

Choosing Between 1L, 2.5L And 5L

The 5L tin is the largest option in the 903 range. It is best for bigger roof repair areas, repeated maintenance work and trade use where smaller tins may not offer enough working quantity.

• Choose 1L: For one small crack, minor joint, small touch-in repair or very local patch.
• Choose 2.5L: For several repair points, repeated gutter details, grouped roof defects or small-to-medium maintenance work.
• Choose 5L: For larger repair areas, broader patching, frequent use and trade roof maintenance jobs.
• Use on dry surfaces only: The surface should be dry, clean and stable before application.
• Do not use as a structural repair: Broken, loose or unstable roof materials should be repaired properly before applying mastic.
• Do not rely on standard paint over bitumen: Many coatings do not bond well to bitumen surfaces.

Technical Notes

• Black fibre-reinforced bituminous trowel mastic.
• 5 litre tin for larger repair areas, broader patching and trade maintenance work.
• Applied by steel trowel, spatula or putty knife.
• Designed for sealing, waterproofing, bedding, bonding and patch repair use.
• Suitable for many clean, dry and prepared roofing or building surfaces.
• Approximate coverage depends on surface condition, repair depth and application thickness.
• Drying note: Sika advises that the mastic forms a surface skin after around 24 hours. The material underneath remains plastic for many months, which helps it tolerate moderate movement after application.

Products To Help With Preparation, Use Or Clean-Up

Before applying the mastic, larger repair areas should be cleaned back properly. A scraper, brush or wire brush can help remove loose material, surface dirt, rust, grit and unstable coating from the areas being repaired.

Porous, friable or difficult surfaces may need priming before the mastic is applied. Use Sika Black Jack 902 Bitumen and Flashing Primer 1L where a compatible bitumen primer is required.

For handling and clean-up after preparation or application, Sika Everbuild Heavy Duty Textured Wonder Wipes can help remove general grime, dirt and residue from hands, tools and suitable surfaces.

For a single small repair, choose the 1L Sika Black Jack 903 size from the side options. For several smaller repair points, choose the 2.5L size where available.

• Specification

  Weight	6 kg
  Manufacturer	Sika
  Reference Code	90305
  Reference Code sika	852674
  Type	Bitumen Trowel Repair Mastic
  Size	5 Litre
  Range	Black Jack
  Colour	Black

• Product FAQs

  Q: What is Sika Black Jack 903 Trowel Mastic 5L used for?
  A: It is used for sealing and repairing larger roof cracks, holes, joints, gutters, flashings, roof penetrations, laps and exterior waterproofing defects.
  Q: What size is this trowel mastic?
  A: This product is supplied in a 5 litre tin.
  Q: When should I choose the 5 litre tin?
  A: Choose the 5 litre tin for larger repair work repeated patching or trade maintenance jobs where a 2.5 litre tin may not provide enough material.
  Q: How is Sika Black Jack 903 applied?
  A: It is applied directly from the tin using a steel trowel spatula or putty knife.
  Q: Can it be used with reinforcing fabric?
  A: Yes. For larger cracks holes or weak areas a closely woven glass fibre membrane can be embedded into the first layer before a second coat is applied.
  Q: Does this mastic stay flexible?
  A: Yes. It forms a surface skin while the material beneath remains flexible to allow a degree of movement in suitable repaired areas.

• Downloads

  Sika Black Jack 903 Bitumen Trowel Mastic Technical Data Sheet
  Sika Black Jack 903 Bitumen Trowel Mastic Product Flyer
  Sika Black Jack 903 Bitumen Trowel Mastic Safety Data Sheet