FireMastic-300: Premium fire & acoustic sealant offering up to 5hrs fire protection
FireMastic-300 is a highly effective intumescent acrylic sealant designed to resist fire, smoke and sound. It flexes, seals, and expands under heat — forming a protective char that keeps fire and smoke from spreading through joints, penetrations and gaps. It’s ideal for walls, ceilings and internal partitions where fire and acoustic performance are essential.
Why FireMastic-300 Works So Well
- Up to 5-hour fire protection — FireMastic-300 delivers one of the strongest fire resistances available from a mastic, providing long-duration integrity and insulation even under severe conditions.
- Fire and acoustic sealing in one — It not only stops fire and smoke, but also offers strong sound reduction (up to 67 dB), making it useful where acoustic separation matters.
- High flexibility and joint movement tolerance — It supports up to 25% joint movement (+/-), making it reliable in dynamic building environments or where structural shifts may occur.
- Versatile substrate compatibility — Suitable for fire rated plasterboard, concrete, masonry, Hebel/AAC, AFS, Dincel, Speedpanel & Korok systems and more.
- Handles a variety of penetrations and gaps — Great for sealing around small cable bundles, metal pipes, cable trays, dampers, perimeter wall seals or linear joints.
- Clean, easy installation — Acrylic, water-based composition makes it easy to tool, smooth, and clean up. Once cured, it can be painted to match surrounding finishes.
Typical Use Cases
FireMastic-300™ is an excellent choice for:
- Linear joints and gaps in fire-rated walls
- A variety of service penetrations for pipes, cables or small cable bundles
- Perimeter sealing around fire dampers
- Offers cost effective solution for steel sprinkler pipes up to 60.3mm OD without any wrap needed
- Internal building joints (e.g. control joints, partition junctions)
- Installations requiring both fire and acoustic separation, e.g. apartments, offices, shared walls
- Compatible with many BOSS Fire products such as FyreBox™, MaxiCollars™, BOSS Batts™, P40-MAK Wrap and Thermal Defence Wrap.
It’s especially useful where multiple wall types intersect — providing a simple, unified sealing solution.
How to Install FireMastic-300
- Prepare the surface: clean, dry, free of grease or dust.
- If a backing rod is required, install it to maintain correct seal depth in accordance with the tested system.
- Apply FireMastic-300™ with a cartridge or foil sausage caulking gun.
- Tool the bead smooth. For best finish, do so within about 5 minutes.
- Allow to tack-dry (roughly 30 min) and cure. Typical cure rate is ~3 mm per 24 h.
- Once fully cured, the sealant can be painted to match existing surfaces.
FAQ
Q: Can FireMastic-300 seal moving joints?
A: Yes. It accommodates joint movement up to +/- 25%.
Q: Can it be used around metal pipes and cable trays?
A: Yes. It’s approved for sealing around steel, copper & iron pipes, steel sprinkler pipes and electrical penetrations amongst many other applications.
Q: Can it be used in concrete and masonry walls?
A: Yes. It works across a variety of different wall systems including fire rated plasterboard, masonry, concrete, AAC/Hebel, Speedpanel, Korok, AFS, Dincel and many common substrates.
Q: Is it suitable for acoustic separation?
A: Yes. It delivers high sound reduction of up to 67db — ideal for areas where sound control matters.
Q: Can it be painted after curing?
A: Yes. Once cured, FireMastic-300™ can be painted to match the surrounding finishes.
Ready to Choose FireMastic-300 for Your Next Project?
If you need a reliable fire and acoustic sealant that is easy to install and simple to specify, FireMastic-300™ is a smart choice.
Whether you are working on a new build, a refurbishment or a complex multi-service project, the BOSS team can help you select the right system and detail it correctly.
Talk to BOSS Fire for:
- Project and specification support
- System selection and detailing help
Installation guidance and documentation.
Want to Know More?
BOSS Fire can provide full technical guidance, installation details and project support. Get in touch if you would like help selecting the right fire stopping system for your build.
