Fire-resisting walls and floors divide a building into compartments, so a fire and its smoke are held in one area for a set time. That only works if the gaps around services are properly sealed. New services added after handover, such as data cabling and pipework, are a common reason fire stopping gets breached. This guide is for FMs, fit-out contractors and building managers who need to make good after other trades have been through.
How breaches happen
- new data, power or AV cables pulled through an existing seal
- holes cut for pipework or small ducts and left open
- old services removed, leaving empty holes
- ceiling tiles lifted and seals above them damaged
- sealant used to fill a gap without matching any tested detail
Many of these are hidden above ceilings, in risers and behind panels, so they often go unnoticed until someone looks.
A simple post-works checklist
- Ask each trade which fire-resisting walls and floors they passed through.
- Inspect risers, ceiling voids and plant rooms where new services run.
- Photograph every opening and note the wall or floor type, the service and the gap size.
- Check whether the original fire-stopping design or specification covers that situation.
- Get the designer or fire engineer to confirm the right product and detail where it doesn’t.
- Have the openings sealed to that detail and keep records.
Checks after M&E works are good practice, not an optional extra.
Why the tested detail matters
Penetration seals are fire tested to BS EN 1366-3 (BSI listing) and linear joint seals to BS EN 1366-4. Results are classified under BS EN 13501-2, for example EI 60 or EI 120. A seal is only as good as its match to the tested detail: the same product, substrate, service type and size, gap, depth, backing and orientation. Mixing products or improvising invalidates the evidence. Our fire stopping explained article covers the basics.
Need the work done? Mastic Doctor covers South East England, London and all of Scotland, with a 12-month guarantee on our workmanship. Send details for a fixed quote.
Sealant is one option among several
Fire-rated sealant is one type of fire-stopping product. Others include collars, wraps, batts, pillows and boards, each specified for different services and openings. A large bundle of cables or a plastic pipe may need something different to a small copper pipe. Where fire-rated or intumescent sealant is the specified product, we install it to the manufacturer’s tested detail, and we’ll tell you if the detail calls for something else. See fire-rated vs intumescent sealant.
Who decides what
Fire stopping design and sign-off belong to the designer, principal designer, fire engineer or building control, depending on the project. The installer’s role is to install what is specified, to the product’s tested detail. In England, Approved Document B covers fire stopping of openings and penetrations (Approved Document B on gov.uk). In Scotland, see our article on Scotland’s building standards.
Records
Keep a log of what was found, what was sealed, with which product and to which detail, plus photos. These records help the next contractor and support the building’s fire safety information. Tell us what records you need and we’ll confirm with the quote. Our fire-rated sealing page explains our part in this work.
Quick answers
Can any fire-rated sealant be used to fill a gap?
No. The product must match a tested detail for that wall or floor, service type and size, gap and depth. Using a product outside its tested detail means there is no evidence it will perform.
Who should check fire stopping after a fit-out?
The person responsible for the building’s fire safety, usually with advice from a fire engineer or the designer. Building control may be involved where works fall under the regulations.
Do you certify fire stopping?
No. We install fire-rated and intumescent sealant where it is specified, to the manufacturer’s tested details. Design and sign-off sit with the designer, fire engineer and building control.
What should we send for a quote?
Photos of each opening, the wall or floor type, the services passing through and the specification or fire-stopping details if you have them. That lets us confirm whether fire-rated sealant is the specified product for each one.
Related services
More advice
- Fire Stopping Explained for Building Owners
- Fire-Rated vs Intumescent Sealant Explained
- Building Safety Act and Fire Stopping Records
- Fire Stopping and Scotland's Building Standards
- Sealant Snagging Before Handover
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.