Firestopping FAQs

Firestopping FAQs: Your Questions Answered

Firestopping is one of those areas of construction where small details can have significant consequences. A penetration that looks perfectly acceptable on completion may bear very little resemblance to the tested detail it is supposed to replicate. A substituted sealant or oversized annular gap can quietly undermine compartmentation long before anybody notices.

That is why firestopping tends to generate so many technical questions on site. Some relate to standards and compliance. Others stem from the realities of refurbishment projects, awkward penetrations, changing specifications, or conflicting advice from different trades. In many cases, the issue is not a lack of products — it is understanding where products can and cannot be used within the scope of testing.

These are some of the most common firestopping questions we are asked at Norseal. They are not exhaustive, and no FAQ can replace project-specific technical advice, but they do address many of the recurring questions we are asked about passive fire protection systems in real buildings.

What is the difference between acrylic sealant and graphite fire sealant?

Standard acrylic fire-rated sealants are typically used in linear joints and service penetrations involving non-combustible services such as copper pipes and cable penetrations. They are also widely used around coated board (batt) systems and for sealing joints between boards.

Graphite or high-pressure exerting (HPE) sealants behave differently. They are designed primarily for combustible penetrations such as plastic pipes, where the service may soften or burn away in a fire. The graphite expands aggressively under heat to close the void left behind.

In practice, HPE sealants can also be used around cables and mixed services, but they are generally more expensive than standard acrylics, so it is sensible to confirm whether the application genuinely requires them.

As always, the key issue is not simply choosing a "fire-rated" product, but ensuring the sealant forms part of a tested system under EN 1366-3 or EN 1366-4.

Why can't all sealants be used with CPVC sprinkler pipe?

CPVC sprinkler systems are sensitive to certain chemical compounds, particularly plasticisers found in some sealants and adhesives. Improper product selection can compromise the integrity of pipework or fittings over time, especially in pressurised systems. That is why compatibility matters just as much as fire performance.

Where CPVC is involved, only tested and approved sealants should be used, and compatibility should always be checked against the sprinkler manufacturer's guidance before installation.

Can you use coating to bond fire batt joints?

No. Coatings and batt sealants perform different functions and should not be treated as interchangeable.

In coated board systems, joints should be sealed using the approved fire-rated acrylic sealant specified within the tested system detail. Ablative coatings are typically used to reinstate exposed edges, cover fixings or repair damaged surfaces, not to form structural or fire-resisting joints between boards.

Mixing products or improvising joint treatments outside tested details is one of the more common reasons batt systems fail inspection.

When should you use a pipe wrap instead of a pipe collar?

Both products are designed to maintain compartmentation where combustible pipes pass through fire-resisting walls or floors, but they are used in different ways.

A pipe collar contains intumescent material within a steel shell fixed to the face of the wall or floor. During a fire, the intumescent expands inward as the pipe softens or burns away.
Pipe wraps provide the same basic function but are designed to sit within the opening itself, typically recessed into the surrounding construction or batt system.

Wraps are often useful where space is limited or where the penetration detail makes a surface-mounted collar impractical. As with all passive fire protection systems, the important point is that the chosen arrangement sits within the tested scope.

What is the maximum gap that can be filled with fire batt?

This depends entirely on the tested system. Some manufacturers have tested coated board systems in apertures up to 2600mm x 2600mm, but that does not mean every batt system is suitable for openings of that size.

Maximum aperture dimensions are influenced by factors such as:

• wall or floor construction
• framing requirements
• support conditions
• service loading
• fixing centres
• movement considerations 

Large openings may require additional framing, support steelwork or alternative firestopping methods entirely. This is where simply asking "how big a gap can batt fill?" becomes less useful than asking whether the proposed installation matches the tested detail.

Can fire-rated foam be used for firestopping?

Not in the way many people assume. Fire-rated PU foams are commonly misunderstood on site. While some products achieve fire test performance in specific linear joints or small penetrations, they are not a universal solution for sealing large openings or complex penetrations.

Foams are combustible materials. Their performance depends heavily on the tested application, joint size and surrounding construction.
Used correctly, they can be effective around door frames, narrow joints and small service penetrations. Used outside the tested scope, they can quickly create a false sense of compliance.

The term "fire-rated" should not be mistaken for "suitable everywhere".

What fixings should be used with fire batt systems?

Fixings should always follow the tested system detail and manufacturer guidance.
Spacing, edge distances, and fixing types vary between systems, but screws are commonly positioned within the overlap zones and typically spaced at 150mm to 300mm centres, depending on the test evidence.

Fixing choice also depends on the substrate:

• drywall systems generally require drywall screws and penny washers 
  
• masonry or concrete requires suitable anchors or concrete screws
• fixing length must account for batt thickness and substrate depth
• fixings to insulation or batt combinations may require Pigtail or Firespring screws

Fixings should also be coated where required within the tested detail, as exposed steel can conduct heat rapidly under fire conditions.

What do putty pads actually do?

Putty pads maintain the fire and smoke performance of partitions where electrical socket boxes or service outlets would otherwise weaken the wall.
In a fire, electrical sockets can melt or deform, leaving openings through which flame and smoke can pass. Intumescent putty pads expand under heat to seal those voids.
They also provide acoustic benefits, which are particularly relevant in residential and multi-occupancy buildings.

What are firestop pillows used for?

Firestop pillows are mainly used for temporary or removable firestopping arrangements.
They are useful where services may require frequent alterations, such as data rooms, industrial installations, or temporary works. Because they can be removed and reinstated, they provide flexibility that more permanent systems do not.

However, pillows alone generally do not provide an effective smoke seal and often require additional treatment, depending on the application.

When should silicone sealant be used in firestopping?

Silicone sealants are generally used where greater joint movement is expected. Standard acrylic fire sealants typically offer lower movement capability than silicone systems. In buildings where structural movement, deflection or thermal expansion is more significant, fire-rated silicone sealants may be the more appropriate solution.

This is particularly relevant around movement joints or external applications exposed to moisture ingress.

As always, only sealants tested for passive fire protection applications should be used. A general-purpose silicone sealant, even if marketed as "high performance", should never be assumed suitable for firestopping.

This Is Part of a Wider Series

This article forms part of a wider series exploring passive fire protection systems in more detail. Alongside this FAQ guide, we look at fire test standards, legislation, compartmentation, cavity barriers and penetration sealing systems in real-world building conditions. Each article is built around the same principle: that compliant firestopping depends on tested systems, competent installation and evidence that stands up to scrutiny.

Next Steps

Most firestopping questions arise when site conditions no longer match the drawings.
That might be an oversized penetration, an unexpected substrate, a late service change, or uncertainty about whether a proposed detail still falls within the tested scope. These are exactly the situations where assumptions start creeping in.

Norseal works with contractors, specifiers and building owners to resolve those issues before they become inspection failures or expensive remedial works. If a detail is unclear, it is worth asking the question early.