FSI Pyrocoustic® Intumescent Mastic (Box of 25)

Availability: In Stock


Pyrocoustic® Sealant is a water based acrylic sealant used to reinstate the fire resistance of wall and floor constructions where apertures are penetrated by multiple services and linear gap seals where wall and floor constructions abut. Pyrocoustic® Sealant is extensively tested for global requirements, it is supplied in 310ml cartridges.

Please contact us if you require this product in 600ml foils.

Pyrocoustic® Mastic is a water based, acrylic, ablative sealant used to reinstate the fire resistance of wall and floor constructions in linear gap seals, where apertures are penetrated by services.

Pyrocoustic® Sealant is extensively tested for global requirements, it is supplied in 310ml cartridges and 600ml foils.

Product testing

This mastic is tested to the following standards:

  • BS EN 1366-3:2009
  • BS EN 1366-5:2006
  • BS EN 1026:2000
  • ASTM E84
  • ASTM E2923:14
  • BS EN 13501-2:2016
  • LEED 4.1
  • BS EN ISO 10140-2:2020

It also carries the following certifications:

  • CE Mark
  • UL Certification
  • Emicode Certification
  • CoC Marking


It can be used to reinstate fire resistance in the following scenarios:

  • through rigid floors
  • through rigid and flexible walls

Also, you can use FSI Pyrocoustic mastic in linear construction joints, single and multi-service penetrations, blank openings and in conjunction with other FSi Ltd. products.

Technical Details

FSi Pyrocoustic mastic is a water-based acrylic sealant.

It has a weight of ~1.6g/cm3.

Purchase this product in either a white or a grey colour.

Shelf life: 18 months when stored correctly.

Sag flow: ~0 mm (WI 018)

Cure rate: ~3mm/24h (in a 23°C environment, 50% r.h)

Skin time: ~40 minutes (in a 23°C environment, 50% r.h)

Determination of change in mass: 12-15% (ISO 10563:2005)

Determination of change in volume: 2-4% (ISO 10563:2005)

Shore A Hardness (28 days): 66/31 (1 second/ 5 seconds) (BS ISO 7619-1:2010)

Do not use in an environment where joints will be immersed in water, or substrates which could emit solvents, oils or plasticisers.

This product is not resistant to water, strong acids, strong bases, oxidizing agents, alcohols and hydrocarbon solvents.


Installation & Operation

Ensure that before applying Pyrocoustic Sealant, the substrate is clean, dry, sound and homogeneous. It must be free from oils & grease, dust and loose particles.

We recommend carrying out adhesion tests before full application, to assess whether a primer is needed or not.

Use a suitable backing material to control the sealant depth if required as per the UL-EU-00500-CPR document.

Upon application, use a gun to firmly apply the sealant into the joint. Make sure that it is in full contact with the sides of the joint.


To improve the appearance of the sealant, using a flat tool over the sealant may be required. This tooling technique would also compress the sealant into the joint which improves adhesion to the joint sides.

All tools and equipment should be cleaned immediately after use with water.


Maintaining Pyrocoustic Mastic

Please follow the maintenance and inspection schedule defined for the building / project.

Ensure that the inspections are completed and recorded by competent individuals at the correct intervals as per the operation & maintenance manual for the building.

Safe Access and Egress should be in place when carrying out maintenance & inspections.

Damaged and tampered sealant should be dealt with appropriately. New product should be installed in line with installation guidance.


Handling & Storage

This product should be stored in a dry, cool environment, with temperatures between 5 and 35 degrees Celcius.

Do not expose to direct sunlight.



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Data Sheets



Cartridges or Foils

310ml cartridges, 600ml foils