Fire-rated construction — and the joints, panels and glazing that decide whether it holds.

Fire-rated glazing is a tested assembly, not a pane of special glass. The glass, the frame, the beads, the gaskets, the fixings and the construction it sits in were tested together, and swapping any one of them for something that looks equivalent leaves you outside the evidence.

Two things decide most jobs. Whether the glazing has to resist radiant heat as well as fire and smoke, which changes what can be used and how close people can be to it; and whether the surrounding wall or partition is the one the glazed assembly was tested into. FRS installs the assembly to its evidence and records what went in, so the next person can tell what they are looking at.

A floor separates one storey from the next, and everything true of a fire-rated wall is true of it — except that a floor is walked on, cut into after the fact, and very often has a second floor built on top of it with a void in between. That void is the part people forget. Left open, the space under a raised floor is a clear path between compartments that nobody can see, above a ceiling nobody opens.

FRS works on all of it. Fire-rated subfloor and access-floor panels where the floor itself has to carry a rating. Fire-rated board and panel decking over a service void, a shaft, a pit or an opening in a slab. Barriers built inside a subfloor void so the space under the floor is divided the way the building above it is. And reinstatement — making good a rated floor that has been cored, cut, trenched or opened up by a later trade and never properly closed.

It comes up across every kind of building we work in: data halls, comms rooms, switchrooms and control rooms where the raised floor is part of the design; office fitouts where a tenancy floor has been opened for services; and operating plant and substations where the floor has been cut into for years and nobody has a record of by whom.

What we are asked for most

• Access and subfloor panels that have to hold a rating, installed to the system the evidence supports rather than to whatever fits the pedestals.
• Fire-rated decking over voids, pits, shafts and slab openings.
• Barriers within a subfloor void, so it is compartmented rather than continuous.
• Reinstatement of a rated floor after coring, trenching or a service change.
• The record of what was done, where, and what evidence it was built to — because the next trade to lift a floor panel will need it.

Fire-rated construction rarely stands alone. It meets penetration seals, ducts, dampers, transits, structural steel, ceilings and the surrounding walls, and each interface is a place where two sets of evidence have to agree. FRS builds to the interfaces rather than up to them, and raises the ones that are not supported before they are closed up.