The indispensable building component – 100% post-consumer recycled PVC-U cavity closers

Cavity closers have become a critical building component that’s now widely used in all commercial and residential new-build projects. They are undoubtedly the simplest and most effective way to seal cavities around wall openings and provide a rigid template for bricklaying and window or door installation.

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Improving thermal efficiency performance

Our unrivalled range of innovative cavity closers won’t just help you meet today’s sustainable legislation, but that of the future.

One of the main Cavalok products is BigBlok. A leading insulated cavity closer system designed for zero-carbon buildings, which means it already satisfies the 2016 Code for Sustainable Homes Level 6.

Benefits at a glance:
  • Manufactured from 100% post-consumer PVC-U
  • Pre-installed polystyrene core enhances thermal efficiency for Part L compliance
  • Time saving clip together assembly – no adhesives or tools required Quick-fit spring clip for fast installation of pre-glazed windows
  • Compatible with most PVC-U window systems as well as timber and aluminium

Cavity Closer FAQ

Check reveal is a construction method of building walls where the brickwork is returned into the opening of between 15-20mm on the jambs. This method is primarily used for severe weather rated areas or if the designer has taken consideration of the added thermal properties that having windows and doors in check reveal provides.
The minimum thermal resistance as set out by the Accredited Construction Details (ACDs) Part L is 0.45_m²K/W
A standard EPS filled cavity closer you cannot use as a direct fix. With our high density CF EPS material you can use a cavity closer as a fixing point.
A hybrid cavity closer is required when the load of the window or door will be primarily over the open cavity and where the standard loading capacity of a standard closer will not suffice. A structural closer will also be used if a direct fix through the window into the closer is used.
Our cavity closer system can be used on timber frame and other frame constructions using our frame hanger system. This system is designed to support the cavity closer from the internal frame prior to the erection of the external skin.
The ACDs state that the minimum requirement for a window to be set back into the cavity is 30mm from the inside face of the external skin. The further the set back of the window frame with the cavity, the better the thermal performance of the junction.
The bracing system spans from jamb to jamb of the cavity closer frame and allows for rigid support for transportation and installation. Optional supports on the corners can be provided for the larger cavity widths. Cavalok corner braces can be provided.
Windows and doors set back a minimum of 30mm within the cavity can be supported by a standard cavity closer as the primary load will be supported by the external skin. If windows and doors are to be installed directly over the cavity, a structural assessment will need to take place by a member of our technical team.
The brick or external course should be built up to cill level for the cavity closer frame to then be inserted and to be used as a guide for building of the jambs.
Domestic dwelling comprising of ground floor and first floor (masonry construction) only needs a non-fire rated cavity closer. Masonry construction more than two stories or of timber construction they must then use a fire barrier (fire rated closer or sock) or wooden pinch baton. Multiple dwellings within one unit, the builder has to provide a fire barrier for continuation of a compartmental or party wall, this also applies to terraced housing. In particular in Scotland, where the majority of construction is timber frame, fire barriers are required.
For more information about the Cavalok range of PVC-U products and support services for specifiers and architects, please call 0300 333 6525.
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