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REDiBOX Wall Recess Former Specification

REDiBOX is a purpose-designed ‘left-in’ component for easy forming of recesses in concrete walls (precast or in situ). REDiBOX is configured to receive the sliding inner sections of TSS and RVK Telescopic Connectors cast into floors or landings. After cementitious grout fill, the connection is ‘unseen’ and fire resistant.
Invisible Connections’ range of permanent recess formers includes REDiBOX PRF-STD (standard version) and REDiBOX PRF-PIN (pinned version). REDiBOX standard version is used where the layout of connectors inherently tie floor or landing in position. REDiBOX pinned version enables robustness requirements to be met where the landing can only be fixed on two ends.

REDiBOX is manufactured from durable and recyclable high density polyethylene (HDPE) and sized to provide generous installation tolerance.

Features and benefits

  • Recess fits within the depth of the floor so that the connection is hidden and clean architectural lines can be realised.
  • Once grouted the recess former is protected from fire so that fire resistance and reaction to fire requirements can be met.
  • Appropriate for installation across all concrete wall construction techniques (slip-form, jump-form or precast).
  • Different floor shapes and connector layouts can be accommodated and robustness compliance achieved.


  • Ribbed monocoque structure on back and sides provides strength and a substantial key to anchor it into the concrete wall.
  • Fully sealed unit ensures the recess will be clean once the face-plate is removed.
  • The rear of the detachable face-plate has an inset perimeter rib, which provides a close fit to the box and also maintains the shape of the recess former under concrete pressure.
  • The face-plate can be nailed to timber moulds or shutters. Alternatively, the integral lugs (two on four sides) provide fixing points to tie-wire the unit to the wall reinforcement (suitable for slip-forms).
  • Recyclable face-plate incorporates a central ‘soft-eye’ into which a hammer-claw can be inserted to pull and detach, revealing the clear recess.


  • REDiBOX PRF-STD: For use with TSS 41, TSS 101, TSS 102, RVK 101. When rotated 90 degrees may also be used with DTS 120 and DTS 150 connectors to support lightweight beam connections and Double Tee floors.
  • REDiBOX PRF-PIN: For use with TSS 81-30 and RVK 101-30 connectors.


  • [REDiBOX PRF-STD] – Standard version, 180 x 120 x 104 mm (internal, w x h x d).
  • [REDiBOX PRF-PIN] – Pinned version, 180 x 230 x 120 mm (internal, w x h x d).


  • REDiBOX PRF-STD: Used where layout of connectors inherently tie floor or landing in position.
  • REDiBOX PRF-PIN: Supplied with a white rebar tie-pin and 3D restraint U-bar with wire-tied crossbar. The white rebar tie-pin is conveniently housed inside the back of the recess former, easily accessed to position it through the hole in the telescopic connector and into the lower pocket of the recess former (thus enabling the axial tie). Alternatively, the entire unit can be secured into position using loose ‘trappings bars’ (not supplied) wired back to the main wall reinforcement.


  • [None]
  • [Foam rod]
  • [Levelling shims]

Guidance for REDiBOX

  • As standard.


  • Durable and environmentally recyclable HDPE.


  • Vertical:
    REDiBOX PRF-STD: ±35 mm.
    REDiBOX PRF-PIN: +30/ -10 mm.
  • Horizontal:
    ±40 mm (minimum).

We have completed installation of our stairs in both cores, using TSS connectors. Everything went smoothly, quickly and easily. The new anti-uplift brackets have done the job perfectly.

Matthew Bialecki, Senior Engineer, J. Coffey Construction Ltd 
Matthew Bialecki, Senior Engineer, J. Coffey Construction Ltd

We were thinking how we could give the architect what they wanted: a finished landing with a shadow gap all around. We used the telescopic connection system from Invisible Connections, which made it a lot easier, both to install the wall recesses and to install the stairs.

Ali Solki, Project Engineer, A J Morrisroe 
Ali Solki, Project Engineer, A J Morrisroe

Telescopic connectors provide us numerous advantages for precast stair installation. Apart from improved time and efficiency, the health and safety gains over traditional support methods are a key driver to satisfy our own needs, as well as those of our clients.

Shane Dunleavy, Project Manager, Morrisroe 
Shane Dunleavy, Project Manager, Morrisroe

Thank you for sending the calculations and installation advice. The new calculation software looks great. Very clear, user friendly and with more design checks than the previous version. It’s a pleasure to see how you are constantly improving.

Stefan Pauceanu, Senior Structural Engineer, Ground Construction Ltd 
Stefan Pauceanu, Senior Structural Engineer, Ground Construction Ltd





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