Firestopping & Fire-Rated Assemblies

Buildings are divided into fire-rated walls, floors and shafts that hold back fire and smoke for a set time, such as one or two hours, so people can get out and firefighters can work. Every pipe, cable and duct that passes through those barriers makes a hole. Firestopping seals those holes with tested materials so the barrier still works. A single missing seal can let fire and smoke race through a building.

• All Trades
• Electricians & Plumbers
• Fire Protection
• Inspectors

Key terms

• Fire-rated assembly: a wall, floor, ceiling or other construction tested to resist fire for a certain time (for example 1 or 2 hours), shown in a listing or design. Fire barriers and fire walls divide buildings into areas. Smoke barriers limit smoke spread.
• Penetration: an opening through a rated assembly for pipes, conduits, cables, ducts or other items.
• Joint: a gap, such as where a wall meets a floor or an exterior wall, or an expansion joint, that needs to be sealed so fire can’t pass.
• Firestop system: a combination of materials and installation details tested together (with the specific wall or floor and the specific penetrating item) and listed by a testing lab. Tests follow ASTM E814 (UL 1479) for penetrations and ASTM E1966 (UL 2079) for joints, and E119 (UL 263) for rated assemblies.
• Fire damper and smoke damper: devices in ducts that close to block fire or smoke at rated barriers. They are separate from firestopping but must be coordinated.

Building and fire codes require firestopping of penetrations and joints in rated assemblies. See Building Codes and International Fire Code (IFC). The details are in the listed system, not in a general rule.

Why firestopping fails

• Missing or incomplete seals where trades cut or drill holes and don’t restore them.
• The wrong product for the wall, the opening or the item, such as ordinary caulk, expanding foam or mortar that isn’t a listed firestop system.
• Changes after inspection: new cables and pipes added to existing sleeves without re-sealing them.
• Poor installation: too little material, wrong depth, no backing, or gaps around the edges.
• Ignoring movement in joints or with plastic pipes that melt, where the seal must expand or collapse the opening.
• No documentation of which listed system was used.

Common firestop materials

Who is responsible

• Every trade that makes or uses a penetration has to see that it is properly firestopped, usually by a trained firestop installer under a coordinated program. In many projects a specialist subcontractor does it, and trades must not leave open holes.
• General contractors and owners should have a firestop plan, a list of the approved systems and an inspection and documentation process, which often includes third-party inspection.
• Building owners and maintenance staff must keep firestopping intact after construction. Anyone who adds cable, pipe or conduit through a rated wall must restore the seal.
• Inspectors check for compliance with the building code and the listings, sometimes using special inspection standards (such as ASTM E2174 for penetrations and ASTM E2393 for joints).

Good practices for installers

• Identify rated assemblies on drawings and in the field before cutting. Look for markings on walls, ceilings and above-ceiling labels, and ask before you drill.
• Use only listed systems that match the assembly, the opening size, the penetrating item and the rating. Keep the system listing or drawing on site.
• Follow the manufacturer’s instructions for material, depth, backing, gaps, cure time and temperature, and preparation of surfaces.
• Train installers. Many manufacturers and third-party programs offer training and certification.
• Label penetrations with a system number, date, installer and rating where required. Photograph before they’re covered.
• Coordinate with other trades, so seals are installed after pipes and cables and before ceilings and walls cover them. Re-seal after any later changes.
• Document and inspect the work, and correct problems before closing walls.

• Don’t use expanding foam, drywall compound or mortar that isn’t listed for the system.
• Don’t leave “temporary” openings, sleeves or open holes in rated walls and floors.
• Don’t stuff insulation or rags in a hole as a substitute.
• Don’t overload a sleeve with more cable than the system allows.

Worker safety while installing

• Chemical hazards: sealants and sprays can irritate skin, eyes and lungs and may contain solvents. Read the SDS, ventilate and wear gloves, eye protection and a respirator if required. See Safety Data Sheets and Respiratory Protection.
• Mineral wool and dust: wear long sleeves and a dust mask to reduce irritation. Cutting cementitious products makes silica dust. See Silica.
• Work in overheads, ceilings and shafts: use proper ladders, lifts and fall protection. See Fall Protection Basics and Scissor Lifts.
• Electrical hazards: be careful around live cables and conduits when working in cable trays and electrical rooms. See Lockout/Tagout.
• Confined spaces and shafts: use permits and follow procedures where required.
• Firestop work near hot work needs fire watch and permits. See Hot Work Permits.

Firestopping checklist

• Rated walls, floors and joints are identified before cutting or drilling
• Every opening is sealed with a listed firestop system that matches the assembly and the penetrating item
• Installers are trained and follow the manufacturer’s instructions; the listing is on site
• Seals are labeled, photographed and inspected before walls and ceilings are closed
• Seals are restored after any later cable, pipe or conduit changes
• Installers use SDS, ventilation and PPE for sealants and mineral wool

Last updated: October 5, 2026