Why are firestopping defects so common in existing buildings?

I have inspected hundreds of buildings in the UK during my career and frequently found the fire safety section of my reports highlighted compartmentation defects that are typically a combination of poor design, coordination and skill.

In recent years there has been a shift to more robust fire safety design, with the introduction of third-party certification schemes for both product and installer competency as well as new regulatory frameworks that aim to address long-standing failings within the industry.

Yet despite this progress, many existing buildings remain unchecked, with either missing or defective firestopping that presents a life‑safety risk.

The go-to industry standard guidance for fire safety design in England and Wales was, and still is, the government legislation Fire safety: Approved Document B and the British Standards Institution's guidance BS 9999 and BS 9991.

The guidance stipulates where lines of compartmentation should exist, what fire rating they should achieve and that service penetrations should be appropriately firestopped.

In most projects, the fire engineer or architect would interpret the guidance and develop a project-specific fire strategy. 

Architects and structural engineers then go on to design how the walls or floors would be constructed to achieve the required fire resistance.

This creates a gap in design responsibility, leaving the contractor to deal with service penetrations on an ad hoc basis without any oversight. 

This can in turn lead to the use of incompatible firestopping products – usually off-the-shelf products from general building material suppliers – or, penetrations would simply be left unsealed and then concealed, due to a lack of knowledge and understanding.

Following the Grenfell Tower disaster, there has rightly been a spotlight on fire safety design in buildings and, from this, a significant shift in how fire safety design is better managed on projects.

Improved design coordination between the project team and specialist subcontractors is now commonplace as a result, as are early engagement with firestopping manufacturers, third-party competency schemes and a re-emergence of the clerk of works role.

It is no easy task, and requires meticulous planning and coordination in the early stages of the design process.

Considering the complex process involved in achieving a compliant firestopping solution, it is no surprise that the existing building stock has suffered an epidemic of defective fire compartmentation.

This is not a sector-specific issue: it affects all building types, including residential, office, industrial, retail and mixed-use developments. The defects often remain hidden or are in difficult-to-access areas that would typically not be inspected as part of a standard due-diligence survey.

Despite this, there are some limited areas where these can be readily inspected, such as plant rooms and riser cupboards, and if visible, it is important to understand what to look out for.

The following defects are those which are most common and can lead to substantial remediation works being required.

1. Missing firestopping. Services passing through walls or floors without any form of sealing or protection to the surrounding opening. This is very common and has been seen in buildings as recently as the 2010s.

2. Sealing with non-fire-rated products. Most commonly, we find expanding foam, either standard or 'fire rated'. Neither would be suitable for service penetrations, nor would they last more than a few seconds in a fire scenario.

3. Oversized apertures where fire collars are intended to be used. This goes back to the importance of design coordination, understanding the pipe diameter and ensuring the core holes are adequately sized to facilitate installation of a fire collar afterwards.

4. Products installed incorrectly. It is common to find that products are not installed in accordance with the manufacturer's instructions. The example below is a head-of-wall detail where mineral wool was installed but did not fill the gaps to the metal sheet profile above.

5. Incorrect product specification. Products may be found to have been installed in a substrate or around a service where they are not certified for use.

6. Chemical incompatibility of products. This defect is less common and relates to the use of chlorinated polyvinyl chloride sprinkler pipework, which can have a chemical reaction with certain firestopping products. This has led to flooding of buildings, causing substantial widespread damage. This is difficult to determine through visual inspection and would require product information to be reviewed.

Understanding the nature and origin of these issues is essential for surveyors to accurately assess risks and provide suitable remedial options to clients. The new role of Principal Designer (Building Regulations) introduced under the Building Safety Act 2022 now provides a framework for how these historical failings can be addressed on projects going forward.

One of the key roles of the new Principal Designer is to plan, manage and monitor all design work in a way that ensures full compliance with the Building Regulations. One outcome is that design gaps are identified from the outset and properly assigned to the relevant competent designer to resolve.

Using firestopping to service penetrations as an example, early collaboration between architect, structural engineer, fire engineer, mechanical and electrical engineer, contractor and specialist firestopping manufacturers should now take place.

This will help ensure risers and structural openings to facilitate service routes are appropriately sized, not only for the number of services passing through but also to ensure a tested firestopping detail is achievable.

While the introduction of the new Principal Designer (Building Regulations) role will undoubtedly help prevent the legacy issues we currently face, it does not resolve the long-standing issues embedded in buildings built before the regulatory changes were introduced.

As a result, surveyors will continue to uncover defects for many years to come, highlighting the ongoing need for intrusive assessments and targeted remediation to manage fire safety risks in older properties.

The following outlines key considerations for high‑level, non‑intrusive technical due-diligence surveys.

1. Information request and desktop review. A pre‑survey request for information should be issued to the building owner or manager. 

In relation to firestopping, surveyors should ask for the building fire strategy, fire risk assessment, as‑built drawings, firestopping quality assurance records, product data sheets, compartmentation surveys and maintenance logs.

Often, limited information will be provided. However, it is essential to always request this, as any omissions will form part of the survey limitations.

2. Review exposed and accessible areas on site. Following a desktop review, the surveyor should inspect all accessible areas of the property where service penetrations are readily visible, such as riser cupboards, plant rooms, bin rooms, basements, car parks, lift rooms, server/comms rooms and meter cupboards.

Hatches and removeable suspended ceiling tiles may provide access into voids. However, health and safety risks should be considered before accessing these areas.

3. Assess the presence and quality of firestopping. Where firestopping is visible at service penetrations, surveyors should consider the following.

• Is the installation labelled by a third‑party certified installer? If so, request supporting documentation and confirm competency.
• Are there cracks, gaps or evidence of movement? Firestopping installed within deflection zones without appropriate detailing often leads to visible cracks and gaps to firestopping materials.
• Where pipework passes through compartments, check for appropriate collars and confirm adequate fixings to the substrate.
• Confirm whether the wall or floor is actually a fire‑rated compartment. Misidentifying compartment walls is common in legacy buildings.

Older buildings often contain historic services that have been partially removed, leaving redundant pipes or ducts unsealed. Even if the original penetration has been firestopped, unsealed pipe ends deeper within the system may still permit cold‑smoke transfer.

It is extremely common in older buildings to find no firestopping at this location and it is often a tell-tale for the detailing of fire doors located in the rest of the building.

After inspecting a representative sample of accessible areas, surveyors should assess whether observed defects are isolated or indicative of systemic issues likely to exist in concealed locations.

Where systemic defects are suspected, an intrusive compartmentation survey should be recommended. If no fire strategy is available, one should be commissioned beforehand to establish the building's intended compartmentation requirements and to inform the scope of more detailed investigation.

Surveyors should also be mindful that compartmentation surveys carried out solely by firestopping contractors can result in overly cautious reporting, particularly where the contractors do not fully understand the building's fire strategy.

Commercial incentives may also drive some contractors to identify every service penetration as a defect, regardless of whether it breaches a compartment line, leading to unnecessary remedial works.

Independent oversight by a competent fire engineer or experienced surveyor is essential to ensure findings are accurate, proportionate and aligned with the building's actual design intent.

As surveyors, we will play a central role in identifying these defects and advising clients on both the life safety and commercial risks.