Cavity Closers

Cavity closers and window formers are important elements of any new build development, protecting from water ingress, damp, heat loss and condensation. That is why we supply them for new build developments across the South West.

These products are widely used by leading commercial and residential housebuilders in the UK, as they provide market leading thermal performance and the most efficient way to seal cavities around wall openings and a template for window and door installations.

Cavalok’s wide product selection makes them suitable for all new build development, closing cavity at window and door opening in almost any size, material, and make-up of wall, enabling specifiers to meet current legislation demands.

Download full Cavalok brochure

BigBlok Cavity Closer

The BigBlok Cavity Closer and Frame Acceptor System is suitable for use in masonry walls with nominal cavity widths ranging from 125 to 300 mm and is compatible with PVCU, timber, aluminium, steel and composite window and doors. The system can also be used in timber-framed and steel-framed buildings. This product closes opening with continuous CFC/HCFC-free insulation, reducing U-values to prevent thermal bridging. In addition, it is super-insulating and has been designed specifically to meet the need of zero carbon.

Download BigBlok Cavity Closer and Frame Acceptor System brochure


FramleBlok is a combination of a cavity fire barrier and a cavity closer former. This product serves as a ring of fire protection around openings in cavity walls, providing more than a 60-minute fire integrity and insulation. Unlike other traditional methods of closing cavities, such as battens in timber frame or returned brickwork, FrameBlok is provided with a very high thermal performance. It is manufactured from recycled PVCu and is suitable for cavities greater than 100mm, and up to 150mm.

Download FlameBlok brochure

Trade Closer

Trade Closer can be used for cavities of 50-100mm and is perfect for refurbishment projects. It provides a high thermal performance insulating and sealing cavities around windows and doors in existing walls. In addition, it also provides an efficient way to improve the damp proof course when replacing a window.

Download Trade Closer brochure

Hybrid Cavity Closer

Hybrid Cavity Closer provides a solution for wider sized cavities up to 300mm. Its new and advanced insulating foam technology allows the loading of heavy A rated windows directly over cavity. Being reinforced with steel for inner and out leaf support, it provides reduced air leakage with the option of a four sided closer at the head.

Structural Closer

Structural Closer can be used for doors and large window openings of 100mm. The former is filled with structural foam inserts, providing you the ability to directly fix through the outer door frame into the cavity closer, removing the reliance on strap fixings. This way, any movement can be reduced after installation. They are mainly used on front, back and French doors.

Download Structural Closer installation guide

BBA Certificates

Download cavity closer British Board of Agrément certificates.

Cavalok Cavity Closer and Frame Acceptor System

BigBlok Cavity Closer and Frame Acceptor System