Firestop Guide

How to Firestop Pipe Penetrations (Plastic vs. Metallic)

Pipe is the most common thing to penetrate a fire-rated wall or floor — and how you firestop it depends entirely on what the pipe is made of. Metallic pipe and combustible plastic pipe behave in opposite ways in a fire, so they need completely different systems.

Metallic pipe: seal the annular space

Steel, copper, iron and cast-iron pipe stay intact in a fire. Firestopping them is straightforward: pack the annular space with the material the UL system calls for (usually mineral wool) to the required depth, then cap it with an intumescent or elastomeric firestop sealant. That is the whole system for most metallic penetrations.

Plastic pipe: the pipe disappears

PVC, CPVC, ABS and PEX soften and melt away in a fire, leaving an open hole for flame and smoke. A bead of sealant cannot close a gap that large — you need an intumescent device that expands with enough force to crush the collapsing pipe and choke the opening shut:

Intumescent collars — surface-mount to the wall or floor, sized to the pipe OD (typically 1.5"–6"). The standard for larger plastic pipe.
Wrap strips — tuck into the annular space before sealing. The flexible option for smaller pipe, tight spaces and retrofits.

See the full range of collars, wrap strips and sleeves →

Collar or wrap strip — which one?

Both crush a melting plastic pipe; the UL system decides which is listed for your conditions. As a rule of thumb, collars suit larger diameters (2"+) and floor penetrations, while wrap strips suit smaller pipe and tight or retrofit spaces. Send us the pipe material, diameter and assembly and we will pull the exact UL system — free.

Frequently asked questions

Do I need a collar or a wrap strip for plastic pipe?

Both are intumescent and both crush the melting pipe — the listed UL system determines which to use. Collars are typical for larger diameters and floor penetrations; wrap strips suit smaller pipe, tight spaces and retrofits. We will match the exact system to your pipe schedule.

How do you firestop metallic pipe?

Metallic pipe stays intact in a fire, so you pack the annular space (usually with mineral wool, per the UL system) and seal it with an intumescent or elastomeric firestop sealant. No collar or wrap strip is normally needed.

Can I firestop a pipe without opening the wall?

Usually yes. Collars surface-mount to both faces of the wall or floor, and wrap strips insert into the annular space around the pipe. Most UL systems require no demolition.

Need it matched and priced?

Send your penetration schedule and we'll pull the UL system and quote it — distributor pricing, same-day shipping, free submittal support.

Browse catalog & pricing →Email sales@firestop-usa.com