Most buildings are divided into compartments by fire-resisting walls and floors. They’re designed to hold a fire back long enough for people to get out and for firefighters to work. But they only work if they’re complete, and every cable, pipe or duct that passes through them leaves a gap.
How fire uses the gaps
A hole for a cable tray or a pipe might look small, but fire and hot smoke move through any route they can find. An unsealed gap in a compartment wall can let smoke into an escape route within minutes, and let fire bypass a wall that was designed to stop it. Gaps above suspended ceilings and in risers are especially dangerous, because nobody sees them.
Building regulations guidance in England, in Approved Document B, requires openings where services pass through fire-resisting construction to be fire-stopped, so the wall or floor keeps its fire resistance.
Common problems
These are the issues most often found in surveys:
- Holes left after new cabling or pipework. An electrician or plumber passes a service through a wall and moves on, without sealing around it.
- Voids left when services are removed. A redundant pipe or duct is stripped out, leaving a large hole behind.
- The wrong products. General-purpose expanding foam, for example, isn’t a fire stopping product unless it’s a tested fire-rated system used exactly as tested.
- Products used outside their tested details. A fire stopping product is only proven for the wall or floor type, the size of opening and the services it was tested with.
- Mixed services crammed through one opening, which few products are tested for.
What good fire stopping looks like
Good fire stopping uses third-party certified products, chosen to suit the wall or floor and the services passing through it, and installed to the manufacturer’s tested details. Depending on the situation, that might be:
- fire sleeves or cable transit systems, which let cables be added or removed later without redoing the fire stopping
- pipe collars or wraps for plastic pipes, which close the opening as the pipe softens in a fire
- fire batts and sealants for larger openings and mixed services, such as around ductwork
- intumescent coatings on structural steel, which swell in a fire to insulate the steel
Installers can also be third-party certified for fire stopping work. Recognised schemes include FIRAS, LPCB LPS 1531, BM TRADA Q-Mark and IFC Certification.
Keeping it right
Fire stopping is easily undone. A few habits help:
- make sure everyone who works in the building knows which walls and floors are fire resisting
- ask contractors how they’ll reinstate fire stopping before they start, not after
- keep a record of what was installed where, with photographs if possible
- have compartmentation checked after significant building or services work, and as part of your fire risk assessment
If you’ve had gaps identified in a fire risk assessment or survey, or you’re planning work that will pass services through fire-resisting walls, see our fire stopping service or get a quote.