What is fire stopping in construction?

Fire stopping, also known as compartmentation, is a fundamental part of passive fireproofing. It refers to the process of filling openings and joints between walls and floors with fire-resistant material, inhibiting the spread of fire between ‘compartments’ within a building.

In this post, we’ll explore the origin of fire stopping regulations in construction. We will then provide an overview of the most common fire stopping methods, as well as some of the most frequent instances of non-compliance with industry best practice.

The origins of fire stopping regulations in construction

Compartmentation and fire stopping originated in the shipbuilding industry. Similar to the construction industry, the walls were often peppered with holes to allow ducts, pipes, and cables to pass from one area to the next. Fire stops were meant to stop fires from penetrating and travelling through these gaps. While used for construction on land it would be some time before regulations regarding fire stopping materials and requirements would be put in place.

The pivotal moment came in March 1975, when a test was performed at the Browns Ferry Nuclear Power Plant using a lit candle. The goal was to discover air leaks, but the polyurethane foam used at the time turned out to be highly flammable. The fire quickly spread, significantly damaging the reactor control cabling. That was considered a significant moment in the use of fire stopping in the nuclear, commercial, and industrial construction fields.

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Another catalytic event was the MGM Grand Hotel Fire in Las Vegas. Commonly considered one of the worst fire-related disasters in U.S. history, 85 people lost their lives and over 600 people were injured. In the aftermath of the fire, it was discovered that one of the main reasons the fire spread so quickly were unfilled openings in joints, electrical and plumbing systems and vertical shafts. The changes in passive fire protection best practice following the fire formed the basis of the numerous fire stopping regulations that companies and contractors abide by today. These include:

• Building Regulations 2019, Approved Document B.
• Regulatory Reform Order 2005.
• BS 7671:2018 – IET Wiring Regulations.

Fire stopping methods and products

There are various methods, materials, and products used for fire stopping. Depending on the construction requirements and environment, these may differ. Below, we look at a few common methods and products and when they’re typically used.

Fire sleeves: pipes and cables

Pipes and cables can pass through different ‘compartments’ within a building. The openings around their entry and exit points between compartments can act as channels for fire to spread. To prevent this from happening, passive fireproofing professionals have a variety of tools at their disposal.

Fire sleeves are fire stops made for sealing the gaps created by pipes and cables passing through walls or ceilings. When there’s a fire, these sleeves expand rapidly to seal the space between the pipes or cables and the surrounding materials. If used with plastic pipes, the sleeve will crush the pipe to ensure that the gap is fully sealed and that no smoke or fire can travel to the next area.

Fire collars: pipes and penetrations

Similar to fire sleeves, fire collars expand under the high temperature of a fire. These collars help maintain fire resistance levels in conjunction with other fire stops and prevent gasses or flames from spreading from one compartment to another.

Fire covers: ceilings

These covers are designed to stop fires in ceilings. Should a fire occur, the cover will immediately begin to expand internally and fill an entire space with a fire-resistant, insulating char.

Fire sealants and gap fillers: door frames, windows, and gaps

As the name implies, fire sealants and gap fillers prevent fire and smoke from spreading through spaces. When heated at high temperatures, these fire stopping materials expand. There are various sealants and fillers, and it’s critical to use whatever one is best suited to the substrate and application.

These firestops can be used around pipes and cables, as well as fire doors and windows. Although fire doors are fitted to be flush with the door frame, any gaps between the two are filled with silicone-based fire-resistant sealing. To enhance their fire resistance, intumescent strips are often attached to the base of the door.

For fire stopping purposes, windows are treated in a similar way to doors. Gaps around the frame are sealed with a fire-resistant material (suitable for the particular substrate), and any cavities around the window space are filled with a thermal cavity barrier (more on this below).

What’s the difference between a cavity barrier and a fire stop?

Despite a similar purpose, cavity barriers and fire stops differ in their applications. Cavity barriers are designed to effectively close a cavity between two building elements, such as between a floor slab and cladding materials or a loft space. On the other hand, fire stops are intended to close a service penetration made through a compartmentation element, such as a pipe going through a firewall.

Common examples of fire stopping non-compliance

While there are fire stopping regulations in place, there are still common mistakes that can lead to a failed fire safety inspection. It’s critical to ensure that the correct fire stopping materials and installation protocols are followed. The four most common fire stop mistakes are:

• Using unlisted fire stopping products. All products used for joint systems must be tested either under UL 2079 or ASTM E1966. If used for wall or ceiling penetrations, it must be tested under UL 1479 or ASTM E817. These installations are very closely scrutinised.
• Using the incorrect or untested fire stopping materials for a particular purpose or application. Fire stopping materials are developed for specific applications, and using the incorrect materials won’t perform up to the required standards.
• Installing fire stops at the incorrect depth within the substrate. Regulations require fire stops to be installed at a particular depth to function properly. It’s a common mistake made by installers who are not fully trained or are attempting to save on project costs. The required depth may also vary depending on the material, movement requirements, and hourly rating.

Of course, the biggest mistake is when a construction contractor tries to circumvent regulations and avoid installing a fire stop. That still occurs today and can have serious repercussions. Obviously, installing testing and approved fire stops are necessary for the safety of those using the building.

The importance of fire stopping

Fire stopping is an essential component of a building’s safety. They’re required to help prevent the spread of fire through the different compartments of a building. Without having fire stops correctly installed, smoke and flames can quickly travel through a building, damaging the property and risking the lives of its occupants. Fire stops also help emergency services to suppress the fire before it spreads beyond control.

Once installed, fire stopping measures need to be monitored regularly and assessed for their effectiveness. Failure to do so could mean that your property is not in compliance with current fire safety regulations, and you could be held accountable in the event of a fire.

Always ensure that the correct fire stopping materials are used and that materials and expertise are supplied by reputable fire stopping companies.

CLM Fireproofing is one of the UK’s leading fire stopping companies. With 35 years of experience, our experts are able to accurately assess fire risk in your buildings and install measures to ensure full compliance with current regulations. If you’d like to know more, get in touch with CLM Fireproofing today.

Disclaimer: This post is intended for educational use only, and should not be relied upon for compliance purposes.