Key takeaways
- Fire stopping keeps compartment walls and floors fire-resisting where services pass through them
- Most failures come from unsealed penetrations, the wrong products and later trades breaking the seal
- General-purpose expanding foam is not fire stopping
- Every seal should match a tested system and be recorded with a label and photograph
Compartmentation: the reason fire stopping exists
Most buildings of any size are divided into fire compartments. Walls and floors built to resist fire for a set period hold a fire in the area where it starts. That protects escape routes, gives people time to get out, supports a stay-put strategy in many blocks of flats and gives firefighters a safer building to work in.
A compartment is only as good as its weakest point. A fire-resisting wall with a hole in it for a bundle of cables is not a fire-resisting wall. Fire and smoke will find the gap, often within minutes, and spread into the next compartment, the roof void or the escape stair.
Building regulations in both nations require compartmentation and cavity barriers in many buildings. England uses Approved Document B and Wales has its own Approved Document B (Wales). The Fire Safety Order also requires the Responsible Person to maintain it once the building is in use.
What fire stopping actually is
Fire stopping is the sealing of openings and gaps in fire-separating elements so that the wall or floor keeps its fire resistance. It is part of what is often called passive fire protection. Typical locations include:
- Pipes passing through walls and floors
- Cables, cable trays and trunking
- Ventilation ducts and extract routes
- Gaps at the head of walls and around frames
- Service risers at every floor
- Joints between walls, floors and the external wall
Products include fire-rated sealants, intumescent collars and wraps, fire batts and boards, pillows, mortars and fire-rated foams. Each is designed for particular materials, sizes and wall or floor types.
Cavity barriers are a related but different measure. They close off hidden voids, such as ceiling voids, roof spaces and cavities in walls and cladding systems, so fire cannot travel unseen through the building.
Why fire stopping fails
Fire stopping surveys tend to find the same problems again and again. Few of them are about poor products. Most are about how and when the work was done.
Penetrations left unsealed
The most basic defect is an open hole. Services are installed, often above a ceiling or inside a riser, and nobody goes back to seal around them. Because the gaps are hidden, they can remain for years.
The wrong product
A sealant tested for small copper pipes will not necessarily protect a plastic pipe, which melts in a fire and leaves an open hole. That needs an intumescent collar or wrap that expands to close the gap. Products used outside their tested scope may not perform, however neat they look.
Expanding foam misuse
General-purpose expanding foam from a builders' merchant is not a fire-stopping product. It burns. Some fire-rated foams have been tested for particular gaps and constructions, but only within strict limits on width, depth and the surrounding materials. Foam used to fill large openings or around plastic pipes is a very common defect.
Missing or damaged cavity barriers
Cavity barriers are easily left out during construction or disturbed during later work, especially in roof voids, above corridor ceilings and behind external cladding. Because they are hidden, they are also rarely checked.
Later trades breaking through
Even a well sealed building does not stay that way. New data cabling, a replacement boiler flue or a new sprinkler pipe can mean someone cutting through a compartment wall and not reinstating the seal. Without a permit system and someone checking the finished work, the damage goes unnoticed.
A simple permit process helps. Anyone who needs to breach a compartment wall or floor must ask first, agree how the opening will be sealed and with what product, and provide a photograph of the finished seal before the permit is closed.
Tested systems and matching the tested configuration
Fire stopping products are tested as part of a system: a specific product, in a specific wall or floor type, with specific services, sizes and gaps. Penetration seals are commonly tested to BS EN 1366-3 and classified under BS EN 13501-2. The manufacturer's data sheet or assessment tells you which configurations have been tested.
The seal on site must match a tested configuration. If the wall is a different construction, the pipe is a different material or the gap is larger than tested, the evidence no longer applies. Where no tested solution exists, an engineering judgement from a suitably qualified person may be needed, and it should be recorded.
Surveys, labelling and records
A fire stopping survey checks compartment walls, floors and cavity barriers against the building's fire strategy or fire risk assessment. It identifies unsealed openings, inappropriate products and missing barriers, and it is often the starting point for a remedial programme. Surveys usually need access above ceilings, into risers and into roof spaces, so some opening up may be required.
Good practice on completion of any fire stopping is to:
- fix a unique label next to each seal, showing a reference, the installer and the date
- take a photograph of each seal, showing the product and the service
- record the product and tested system used for each location
- keep the records with the fire safety information for the building
These records let a future assessor, contractor or inspector see what was installed and whether it has been disturbed. In England, higher-risk buildings must also keep accurate information as part of the golden thread under the Building Safety Act 2022.
Choosing an installer
Fire stopping is specialist work. Look for an installer who can show training, product knowledge and independent evidence of competence. Third-party certification schemes such as FIRAS, LPCB and BM TRADA Q-Mark are examples of what to look for. Whoever installs it, check the finished work and records before ceilings go back up.
At Vocus Fire Safety, fire stopping surveys and remedial works are carried out in-house by our team, with records held in the Vocus Fire Safety Portal.