Compartment walls often stop at the suspended ceiling. The void above can run the full length of the floor — an open corridor for smoke and flame that nobody ever sees. Gemini AMPM installs cavity barriers and fire barriers as tested, certificated systems, and surveys existing voids for the defects that quietly undo them.
Building regulations guidance is blunt about concealed spaces: cavities must be closed at their edges and around openings, and extensive voids must be subdivided, because a hidden cavity lets fire and smoke bypass every wall beneath it. Suspended ceilings, raised floors, roof voids and external wall cavities all qualify. If a compartment wall stops at ceiling-tile height, the void above must carry the line to the soffit — otherwise the wall is theatre.
We install cavity barriers and fire barriers as complete tested systems: rigid barriers where the construction suits, and flexible, wire-reinforced barrier systems for large roof and ceiling voids, hung, lapped and sealed exactly as the manufacturer tested them. Fixings, supports and penetrations follow the tested detail, with fire resistance specified to match the line the barrier is defending — typically 30, 60 or 120 minutes.
The same defects appear in survey after survey. Barriers that stop short of the soffit. Barriers sagging off their fixings because nobody supported them properly. Neat slices cut for new cabling and never resealed. Laps left open. Foam used where a tested closure was needed. And, above more partitions than you would hope, no barrier at all — because the ceiling grid hid the omission from every handover inspection since.
Finding them is the point of looking. We survey voids with the compartment drawings in hand, grade and photograph each defect, and reinstate barriers as complete tested systems rather than patching what is there. Before-and-after evidence is referenced and handed over for your records. Where defects point to something bigger, the findings feed straight into a wider passive fire programme — barriers rarely fail alone.
A cavity barrier closes or subdivides a concealed space — a ceiling void, raised floor or wall cavity — and typically needs 30 minutes of fire resistance. A fire barrier is the broader term: where a compartment line runs through a void, the barrier above may need to match the full 60 or 120 minutes of the wall below. The distinction matters when specifying, because installing a 30-minute product on a 60-minute line is a defect with a certificate.
Because fire follows the path of least resistance, and an open void is exactly that. Smoke and flame entering a shared ceiling void can pass over the top of walls, drop into rooms far from the fire and cut off escape routes before alarms in those areas trigger. Barriers close the shortcut, holding fire within the same lines the visible walls define. The building looks compartmented from the corridor; the voids decide whether it actually is.
Assume not until someone looks. Data cabling, pipework and duct runs are routinely threaded through voids years after the barriers went in, and the trades involved rarely reseal what they cut. It is the single most common defect we find. A void survey is quick and non-destructive: tiles lifted, barriers traced, breaches photographed and priced. If your building has had a refit, a rewire or a new tenant fit-out since the barriers were installed, a survey is overdue.
A named engineer, not a call centre, comes back within 24 hours. Tell us the building and what you’re dealing with, and we’ll scope it properly.