Fire stopping and passive fire protection for commercial buildings

Compartmentation is the principle behind passive fire protection: a building is split into sections, or compartments, using walls, floors and doors built or upgraded to resist fire for a stated period, usually 30, 60 or 90 minutes depending on the building’s size, use and height. A fire starting in one compartment is intended to stay there for that period, rather than spreading through the building unchecked, which protects people moving through other parts of the building to reach an exit and limits the damage before the fire is brought under control.

A compartment line is only as strong as its weakest point. Fire-rated walls and floors provide the bulk of the resistance, but every door, every service penetration and every gap left where two elements meet has to match that same rating for the compartment to work as designed. That is why passive fire protection is rarely a single job: it means treating the wall or floor, the doors within it, and every pipe, cable and duct that crosses it as one connected system rather than separate items.

Fire doors are one part of that system, holding the line at door openings in the same way that fire-stopped penetrations hold it around services. We cover fire door specification, installation and inspection in detail on our fire doors page; here, we focus on the walls, floors, penetrations and voids around them.

Fire does not only travel through occupied rooms. Ceiling voids, raised floor voids, roof spaces and the cavities inside partition walls can let fire and smoke move between compartments even where the visible walls and floors are intact, because those hidden spaces often run continuously above suspended ceilings or below raised floors without being divided in line with the compartments below. Cavity barriers close off these voids at compartment lines, restricting a fire to the same footprint below the ceiling as above it.

Cavity barriers and voids are also where fire stopping is most often missed, because the work happens above a suspended ceiling or beneath a raised floor where it is out of sight once the fit-out is finished. A void that looked correctly fire-stopped at first-fix stage can be compromised later by cabling contractors, data installers or maintenance teams working back through the same space without reinstating the barrier they disturbed. We check ceiling and floor voids as part of any compartmentation survey, since a wall that is correctly fire-stopped at floor level can still fail if the void above it was never properly closed off.

Fire stopping needs checking periodically rather than assumed to remain intact once installed, because most damage to it happens through ordinary building use: new cabling run through an existing wall, a pipe replaced without the collar being refitted, or a hole cut for maintenance access and never made good. An inspection identifies where seals have failed, where penetrations have been added or altered since the last check, and where fire doors, walls or dampers within the compartment line have been damaged or compromised.

Where an inspection finds a defect, we carry out the remedial work needed to restore the compartment line, whether that means resealing a penetration, replacing a damaged cavity barrier, or making good a wall or floor that has been cut into since it was last fire-stopped. We record what was found and what was done, so the building has an up-to-date picture of its passive fire protection rather than a one-off survey that goes out of date the first time a contractor is back on site.

What compartmentation needs to achieve is consistent, but where the risks concentrate varies by building. Offices and retail units typically need fire stopping around riser cupboards, comms rooms and plant areas where services are concentrated. Warehouses and industrial premises often have larger service runs and bigger openings between compartments, and may have had multiple phases of fit-out and refit that each disturbed the fire stopping put in during the last. Older commercial buildings and converted premises can have compartment lines that were never fully fire-stopped to begin with, particularly where floors or partitions were added after the original construction. We take these differences into account across the industries and premises we work with, rather than applying a single specification everywhere.

Listed and historic buildings raise a further set of questions, since original walls, floors and joinery often cannot be altered or fire-stopped using standard methods without affecting the building’s protected fabric. We cover how compartmentation and fire stopping are managed sensitively in these buildings on our heritage and listed building fire safety page.

If you need a compartmentation survey, fire stopping around service penetrations, or remedial work identified by a fire risk assessment, get in touch through our contact form with a few details about your building and what prompted the enquiry. We will come back to you to arrange a site visit.