A Company spokesman commented that most circular windows are in the popular 450mm to 900mm range.
However, the diameter of circular openings for industrial applications can be up to three metres and regardless of whether of aesthetic or functional purpose, all require damp protection where they punctuate the cavity wall.
This is provided by the Type K Cavitray that envelops the circular frame promoting 360-degree protection.
The Cavitray actually sleeves the frame outside edge so there is no direct contact with the damp masonry.
The main body of the Type K rises upwardly within the cavity ensuring separation between inner and outer skin.
When insulation is also required, a thermal collar that ‘rings’ the opening provides this.
‘Whilst such openings are commonly called bulls eyes, not all of them are circular’ commented the spokesman.
‘We are regularly required to produce elliptical models and sometimes designs require an arrangement of two or more interconnecting sections.’
Water that penetrates masonry above and around a circular or elliptical opening eventually gravitates and discharges at the bottom of the opening, having tracked around the protected frame. ‘That is why we mould in a protective skirt’ commented the spokesman, ‘to ensure all such water is controlled and cannot track inwardly.
More water accumulates at the bottom of a circular opening than at the top – exactly the opposite to what happens over openings with horizontal heads.
The choice of masonry also influences water behaviour.
Perforated bricks for example can act as multiple vertical conduits via which penetrating water can gravitate more speedily.
An increase of 35%+ in the speed at which water permeates is not unusual’.
Type K circular Cavitrays for popular sizes are normally available from stock.
Sizes up to 3 metres diameter are manufactured to order by the bespoke division of Cavity Trays of Yeovil.
The lead-time for such bespoke requirements is expected to halve once the unit is operational.
Production unit operational from 4th January 2011.
Cavity Trays of Yeovil