How to check a fire-rated sealant system

Before choosing a product, pin down what you’re sealing. Is it a linear gap in a wall, a gap in a floor, or a pipe or cable passing through? Note the construction, its thickness and the rating it needs. The fire engineer’s drawings set the required rating, and the seal has to restore it.

The SCDF Fire Code (clause 3.12) requires openings in fire-resisting walls and floors to be kept small and filled with fire-stopping material whose performance has been proven by test.

Fire stopping is life-safety work. Final approval belongs to the project’s fire engineer or Qualified Person, not the sealant supplier.

Pereseal FR is an intumescent acrylic. At about 180°C it expands to two to three times its volume and chars, closing the gap against fire and smoke.

Warringtonfire tested it to BS 476 Part 20 as linear gap seals in aerated concrete walls and floors, over polyethylene backer rod, across a range of joint widths and depths up to 50 mm wide. It held integrity for up to four hours. Insulation times depend on the joint size and on whether the seal is in a wall or a floor.

So “up to four hours” is accurate, but the rating you can claim depends on which tested joint matches yours. The full test report, with every joint size and result, is in our technical library.

• Wall or floor, and its construction and thickness
• Joint width: FR is rated for joints up to 50 mm wide
• Sealant depth
• Backing: the tested joints used polyethylene backer rod
• Linear gap or service penetration, and if it’s a penetration, what the service is

If your joint falls outside what was tested, extra sealant won’t fix it. A deeper bead or a different backing changes how heat travels through the joint. You need a tested detail that matches, or a formal assessment accepted by the fire engineer and the authority.

Don’t swap in another “fire” sealant, mineral wool of unknown density or foam filler. The rating only holds with the components that were tested. For pipe and cable penetrations, ask us for the evidence that covers your service before you specify.

FR bonds to most porous building materials without primer, and can go onto damp surfaces but not wet ones. Fit the backer rod at the right depth, fill the full depth, and tool with a damp spatula or soapy water before it skins at around 25 minutes. Keep it dry for 24 hours. It takes paint once dry.

Check the depth before the joint is covered. A neat face tells you nothing about what’s behind it. Photograph each joint with a scale, and note the location, product, batch and detail reference. Hand the record to the building owner. When someone later runs a new cable through, it tells them which seal they’ve disturbed.