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.
But 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.
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 is naturally drained forward. Unlike traditional cavity stops, the angled top guards against water tracking towards the inner skin as there is no horizontal surface to be usde as a bridge.
Caption Cavity 240 Type SAF multi-functional Cavity Stop vertical use (party walls)
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 maintain all integrities. The Cavi 60 prefix identifies the stop as having a sixty minute fire rating. BS 476 tested / certification
Type SAF Stop
Permanent profile
- 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
