"Every building that is divided into more than one area of different occupation must be designed and constructed in such a way that in the event of an outbreak of fire within the building, fire and smoke are inhibited from spreading beyond the area of occupation where the fire originated."
Maintaining a clear cavity is the usual objective when constructing a cavity wall, but there are occasions when doing the opposite is required if the structure is to satisfy several requirements.
Cavity stops of various styles are produced for installation horizontally and vertically. Passive rectangular profiled stops close the cavity permanently. Intumescent stops leave the cavity partially open and rely on heat to activate closure.
Now there is a third type of cavity stop that offers benefits not available with these alternatives.
The Type SAF cavity stop from Cavity Trays of Yeovil is a passive parallelogram stop that provides both fire-stopping and acoustic arrestment within the cavity. Where Part E requirements call for buildings to have both fire and acoustic stop provision, a Type SAF stop can be used to fulfil both functions in one product installation. The need to have separate acoustic stops with separate traditional or intumescent stops is eliminated. One operation and one cost.
Being a permanent passive barrier means it is in place to also prevent the spread of smoke that generally manifests and can be drawn through cavities in advance of heat and fire. (Statutory regulations state smoke must be inhibited from spreading beyond where a fire originates).
The parallelogram profile with a sloping top and sloping bottom is used to advantage. The shape can act as its own dpc/deflector and any water penetrating the masonry above drains forward. In contrast an unprotected traditional cavity stop with a horizontal upper surface can act as a bridge for water to track inwardly.
It makes sense to amalgamate rather than have separate acoustic and separate fire stops in a wall. The Type SAF (sloping+acoustic+fire hence its name) shape also permits adjoining lengths to simply lap either above or below a neighbouring length and in so doing the sloping advantage, the acoustic advantage and the fire and smoke stop qualities are maintained. Concerns about continuity with end to end butting need not arise.
The Type SAF is passive and not reliant on activation to change shape to function. Its shape and purpose remain unaltered. One knows its presence is as installed and passive containment is fully in place to prevent smoke, fire, and sound journeying through the cavity.
Acts as acoustic stop
Acts as one hour rated fire stop
Smoke spread prevented at all times
Integrity maintained via lap linking lengths
No activation and shape change required to function
Shape deflects water forward to prevent bridging to inner skin