Walls
Enquire:
www.dcep.co.uk Tel: 01630 673000 Fax: 01630 673247 Email:
info@directcontactexhibitions.com Post: use the Enquiry Sheet Closing Cavity Walls?
Consider Rotational Movement + Fire and Acoustic Stopping
Many forms of construction such as building with a timber-frame inner skin require the designer to be aware and make provision to accommodate differential movement. The extent of total movement increases as the building gets higher. (As a rule of thumb a masonry external skin has a tendency to slightly rise as it dries out, 2.5mm per storey of clay masonry) whereas an internal skin of timber will shrink and move downwards. (See UKTFSA publication for advice).
Movement probability also increases as the cavity gets wider. So wherever there is connection between inner and outer skins there is further potential for movement conflict to manifest as cracking. This is because of the see-saw effect wherein upward or downward movement becomes more pronounced as it becomes more distant from the pivot point. Therefore, the way in which the reveal is closed can help reduce the potential for cracking and there are now Caviclosers to help address this issue.
The WCA Cavicloser (WCA stands for Wide Cavity Applications) uses accompanying ties to secure its outer edge to the masonry skin whilst the inboard edge is screwed or nailed directly into the timber inner leaf through the face flange. This section of the closer features a friction fit relationship with the rest of the closer body permitting the arrangement to benefit some expansion and contraction provision.
A version of the type WCA can also be supplied in a fire-rated format. The Cavi 60 type WCA identifies it as being tested (BS 476) to provide 60 minutes fore integrity rating.
Cavi 60 Type WCA reveal cavicloser. Available to suit a range of cavity widths
Elsewhere in the cavity there is a requirement for buildings with more than one area of different occupation to be so designed and constructed “that in the event of an outbreak of fire within the building, smoke and fire are inhibited from spreading beyond the area of occupation where the fire originated”.
The Cavi 60 Type SAF is a cavity stop with a difference supporting a parallelogram profile and providing passive fire-stopping and acoustic arrestment within the cavity. Importantly the parallelogram profile with a sloping top and sloping bottom removes the risk associated with conventional stops as any water penetrating the masonry above always drains forward. (There is no horizontal surface via which water can track inwardly). It also makes joining adjacent Cavi 60 Type SAF lengths simple and straightforward as they stagger-lap to maintain, fire, smoke and water control in a manner not possible with conventional cavity stops. Products are manufactured by Cavity Trays Ltd, the only cavity tray manufacturer awarded European Technical Approval.
www.cavitytrays.co.uk Reader Enquiry: 27 See Cavity Trays at the DCE CPD events 01935 474769
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Reader Enquiry: 28
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