TIMBER FRAME CAVITY BARRIER 551 is designed to prevent passage of fire through concealed voids within the external fabric of a timber frame building.

The polythene enclosed rock fibre barrier is manufactured in bespoke sizes to suit the specified cavity width.

The barrier is stapled to the inner timber substrate prior to brickwork being erected and is compressed into the cavity.



Timber Frame Cavity Barrier 551 assists in satisfying requirements of guidance documents such as Approved Document B and The Scottish Technical Handbook.

The product reduces flanking sound transmission at separating wall and floor junctions and complies with Robust Detail (Appendix A) as a “cavity stop”.

Suitable for both vertical and horizontal positioning to the edge of cavities, around openings, at separating compartment lines and to sub-divide cavities.


• Designed for installation within masonry/timber frame cavities
• Accommodates a maximum void of 175mm
• Easy installation process
• Installed under compression
• For voids up to 150mm a minimum compression of 15mm is required, thereafter 20mm compression is required up to the maximum void of 175mm
• Tested and assessed to the general principles of BS 476-20: 1987
• Suitable for both vertical and horizontal orientation
• Solutions available offering either 60 minutes or 120 minutes fire resistance performance
• When installing it may be necessary to consider additional use of DPC’s and/or cavity trays in line with relevant Building Control guidance.

Product Performance

Cavity WidthStop Sock Size required for 60 minutes integrity/15 minutes insulationStop Sock Size required for 120 minutes integrity/60 minutes insulation
50mm65mm x 65mm65mm x 150mm
60mm75mm x 90mm75mm x 150mm
75mm90mm x 120mm90mm x 150mm
85mm100mm x 120mm100mm x 150mm
100mm115mm x 120mm115mm x 150mm

Other sizes are available

Contact Us