There is usually a horizontal gap between the edge of a floor slab and the inside face of precast cladding. Unless dealt with, this gap would allow flame to spread between floors in the event of a fire. Similar conditions can also exist at a vertical joint between units and a shear wall. To close this gap a fire stop material must be inserted.
Typical materials are non-combustible mineral wool .
The material is cut to fit the gap between the slab and the cladding, allowing 3mm – 5mm compression when fitted.
Supporting brackets are typically required at 450mm centres as shown. The brackets should be mechanically fixed to the floor slab using metal fixings suitable for use in masonry.
If the gap is wider than 250mm, then the joint between sheets may need to be sealed on top with adhesive aluminium tape.
The firestop must extend between two non-combustible surfaces. If the inner face of the cladding has pre-fixed insulation, then it is important that this is stopped off to allow the firestop to contact the face of the concrete cladding. If the firestop is fitted after erection of the cladding, then the insulation must be stopped some way above the firestop to allow installation. The insulation must be re-instated after the firestop is fixed.
There are available alternative methods including mineral wool with a sprayed-on treatment on the top. This can also be taken into account when considering air leakage.