Renovation

Fire-Stopping: Ask for the Photographs Before the Walls Close

Expanding foam is not fire-stopping. Every service penetration needs a tested seal, and Regulation 38 entitles you to the record. Ask before the boards go on.

By Vladimir Castravet·

Here is a simple way to test a builder: ask for photographs of every wire and pipe before the walls are boarded. Once plasterboard goes on, nobody looks behind it again — which is exactly where corners get cut. And you are entitled to the record anyway: Regulation 38 makes handing over fire safety information a legal duty. Our renovation work and loft conversions both live or die on this detail, and the estimator prices it as part of the build rather than as an extra.

What fire-stopping is

A fire-separating element — the wall around a protected stair, a compartment floor, the wall between a house and an integral garage — is built to hold fire back for a stated period. In a house that baseline is REI 30: thirty minutes of load-bearing capacity, integrity and insulation, with fire doorsets at E 30.

That rating belongs to the element as built. The moment somebody drills through it for a soil pipe, a cable, a duct or a joist hanger and leaves a gap, the rating is gone at that point — and fire and smoke travel through gaps faster than through anything else in a building.

Fire-stopping is the sealing of every one of those joints, imperfect fits and service openings so the element keeps the resistance it was designed to have. It is one of the last things done before boards go on, and one of the first things to disappear.

The figures

| The rule | What it requires | Source | |---|---|---| | The general rule | Every joint, imperfect fit and opening for services through a fire-separating element should be sealed with fire-stopping so the fire resistance of the element is not impaired. | AD B Vol 1 §9.1 | | Baseline in a house | REI 30 is the baseline for fire-separating construction in dwellinghouses; fire doorsets E 30 (FD30). | AD B Vol 1, Table B4 | | Pipes through a fire wall | Three permitted routes: a proprietary tested sealing system (any diameter), a restricted diameter per Table 9.1, or sleeving. | AD B Vol 1 §9.2–9.5 | | Pipe diameter limits | Between dwellings: 160mm high-melting-point metal; 160mm stack / 110mm branch for uPVC, lead, aluminium or fibre-cement in an enclosure; 40mm any other material. | AD B Vol 1 Table 9.1 | | Sleeving | Maximum nominal internal diameter 160mm, sleeved in metal that will not soften or fracture at 800°C. | AD B Vol 1 §9.5 | | What is not fire-stopping | Materials must be reinforced with or supported by materials of the appropriate class. Expanding foam alone is not fire-stopping. | AD B Vol 1 §9.25–9.27 | | Cavity barriers | Provided at the edges of cavities, around openings, and to subdivide extensive cavities. Not the same as fire-stopping. | AD B Vol 1 §8.1–8.6 | | At roof level | Fire-stopping carried over the full thickness of the wall and up to the underside of the roof covering, boarding or slab, and extended into any eaves. | AD B Vol 1 §7.4 | | Smoke alarms | At least one on every storey. Grade D1, mains with battery back-up, interlinked. Sited on the ceiling at least 300mm from any wall or light fitting. | AD B Vol 1 §1.2–1.14 | | The 4.5m rule | Escape provisions step up at each storey more than 4.5m above ground level — which is why a loft conversion on a two-storey house triggers a protected stair. | AD B Vol 1 §2.1–2.6 | | Handover | Fire safety information must be given to the building owner on completion. A legal duty, not a courtesy. | Building Regulations 2010, reg. 38 |

Approved Documents are statutory guidance to the Building Regulations 2010 for England. Compliance is judged against the Requirements in Schedule 1; your building control body has the final word on your specific building.

Where it goes wrong

Expanding foam. It is fast, it looks tidy, it fills the hole, and it is not fire-stopping. This is the single most common thing found behind plasterboard on domestic work.

The pipe nobody collared. A plastic soil stack passing through a compartment floor melts early in a fire and leaves an open shaft between storeys. That is what an intumescent collar is for — it expands under heat and crushes the pipe closed.

Downlighters. A protected ceiling perforated by a dozen unrated downlights is a protected ceiling with a dozen holes in it. Fire-rated fittings or hoods exist precisely for this.

The loft hatch and the top of the stair enclosure. Fire-stopping has to be carried over the full thickness of the wall and up to the underside of the roof covering, and extended into the eaves. Stopping at ceiling level leaves the route that matters most open.

Cavity barriers confused with fire-stopping. They are different jobs. Fire-stopping seals a penetration through an element; a cavity barrier subdivides a concealed void so fire cannot travel unseen behind the finishes. You can have one perfectly and lack the other entirely.

Why this is the best test of a builder there is

Almost everything else you buy on a renovation, you can inspect. You can see whether the tiling is straight, whether the paint is even, whether the kitchen doors line up. If you do not like it, you say so.

Fire-stopping you will never see. It goes in on a Tuesday and vanishes on a Wednesday. Nobody will look at it again unless there is a fire or you sell the house and a surveyor gets curious. It costs relatively little to do properly, it takes patience rather than skill, and there is no commercial consequence to skipping it — which is precisely why it is the honest test.

So ask. Not aggressively, and not as an accusation: “Can you photograph the penetrations before you board? I’d like them for the file.”

A good builder will already have them. Ours photograph every covered element as a matter of course — foundations at bearing level, steel bearings and padstones, cavity trays and weep holes, fire-stopping at every penetration, insulation, drainage before backfill — dated and indexed, because on a job where everything is photographed there is nothing to argue about later.

A builder who finds the question strange has told you something worth knowing, at no cost, at the exact moment you can still act on it.

The inspection that matters

The first fix / pre-plaster inspection is where structure, fire-stopping, cavity barriers, insulation and services are looked at together, before they disappear behind plasterboard. It is one of the notifiable stages, and like every other one it closes permanently the moment the work is covered. The only remedy for a missed inspection is opening the work back up.

That single fact is why the photographs matter more here than anywhere else on the job. An inspector attends once. A photograph lasts.

At completion, Regulation 38 requires the fire safety information to be handed to you, alongside the completion certificate, the Regulation 40 building information and the competent-person certificates. Ask for all of it in one file. In year three, when a question comes up, the answer is either in that file or it does not exist.

The same logic applies to the details that keep water out — the damp-proof course and the weep holes are equally invisible and equally permanent.

The takeaway

Fire-stopping is the clearest test of a builder there is, because it is work you will never see. Ask for the photographs before the boards go on. A good builder is proud of the parts you cannot see — and Regulation 38 means you are entitled to the record anyway.

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