Fire batt, sometimes written batten or batting, usually means a dense mineral wool slab coated on one or both faces with an ablative or intumescent compound, used to close a hole in a fire separating element. The material is straightforward. Where installations fail is in the detailing, and in the confusion between two different jobs that use similar looking products.
Cavity barriers
A cavity barrier closes a concealed void so that fire and smoke cannot travel unseen through it: within roof spaces, behind cladding, in floor voids, around the perimeter of compartment lines. It has to be continuous and tightly fitted to both faces of the cavity, and it has to be supported so that it stays there. A barrier with a gap at the top is a barrier only in the drawing.
Penetration seals
Where a service passes through a fire separating element, the hole around it is sealed to restore the element's performance. Coated batt is a common solution for larger openings carrying several services, with collars, wraps or sealants around individual pipes and cables depending on what they are made of. Plastic pipes need a collar that crushes the pipe as it softens; metal pipes conduct heat and need their own detail.
Why the detail matters more than the material
Every one of these is a tested system: the batt, its thickness, the coating, the supporting construction, the services passing through it and their spacings. Adding a cable to a sealed opening after the fact, without reinstating the seal correctly, is the most common defect found in risers. So is a batt friction fitted with no coating on the reverse face, which looks finished from the access side.
Evidence and access
Fire stopping is buried by the next trade, so the record of it is the only evidence anybody will ever have: photographs, locations, the system used, and who installed it. Third party certified installers produce that as a matter of course. Where a building has no such record, establishing the state of its fire stopping means opening risers and ceilings.
Questions people ask about fire batten
Is fire batting the same as ordinary mineral wool?
No. The density and the coating are what make it a tested system. Ordinary insulation stuffed into a hole is not fire stopping, however much of it is used.
Who should install fire stopping?
Somebody working to the system manufacturer's instructions, ideally under a third party installer scheme, and leaving a record of every seal.
How is existing fire stopping checked?
By inspection with access, which means opening risers and ceiling voids at sample locations. It cannot be checked from a corridor.