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FERBOX Reinforcement Continuity System

Former BBC Television Centre, White City W12

FERBOX Reinforcement Continuity System

Exchange Square, Birmingham

FERBOX Reinforcement Continuity System

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FERBOX Reinforcement Continuity System

FERBOX provides the continuity between wall and floor reinforcement. This continuity strip solution is manufactured to precise application requirements and is in daily use by the industry’s leading concrete frame contractors.

Invisible Connections’ manufacturing scope is unrivalled in this product sector, so engineers and contractors benefit from bespoke fabrication to site specific dimensions without the need for any on site modification. FERBOX customers can therefore have confidence that design intent and quality assurance will be met as well as timely delivery and ease of installation.

Good practice as standard practice

For design intent and construction practicalities to be achieved, as well as the quality assurance needs of professional stakeholders to be met, the UK concrete reinforcement sector adopts this process as standard:

  • Concrete reinforcement is specified (to BS4449:2005+A3:2016) and CARES approved.
  • ‘Cut and bent’ requirements are designed to a range of shape codes (BS8666:2005 refers) which provide the basis for designers to define all dimensions to the needs of each project.
  • After careful quantification, to avoid wastage, reinforcement is manufactured to order by CARES approved fabricators.
  • Bundled and uniquely labelled to aid installation, reinforcement is delivered on schedule to site.

This rationale also applies to threaded couplers.

Yet when it comes to reinforcement continuity strip, such checks are often inexplicably dismissed. What is more, since reinforcement continuity strip is subject to the additional demands of rebending on site, it should result in higher levels of scrutiny, not less.

If you would like to see our products in action, please have a look at our videos in the resources area.

Choose the appropriate FERBOX shape for your project requirements below. Alternatively, you can order multiple FERBOX shapes at the same time using our All Shapes Scheduling Form, which includes a guide to every shape option in the FERBOX range. Alternatively, download our Off the Shelf Scheduling Form.

Our CPD seminars and webinars explain the practicalities and theory of using Invisible Connections products and are illustrated with real world examples. If you’re an architect or engineer who would like to attend, please sign up here.

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FERBOX reinforcement continuity strip

FERBOX Reinforcement Continuity System
95% of FERBOX is made-to-measure, providing optimum efficiencies for concrete construction by satisfying design requirements, saving costly wastage and mitigating health and safety risks.


Designed to maintain structural continuity across construction joints in reinforced concrete structures. Easy, quick and reliable installation. Bespoke and off-the-shelf shapes available.

Choose FERBOX by application

All Specials Range

Specials Shape 21 Range

Specials Shape 11 Range

Specials Shape 00 Range

Specials Shape 13 Range

Specials Pull Out Links Range

Selecting the right product

Find below which Invisible Connections’ products are best suited for your project requirements, or download our at a glance Product Selection Guide to view the entire product range, features and benefits.


Product NameFeaturesBenefits
Specials range 19 different bar shape configurations, almost infinitely variable to application requirements, in bar diameters 10, 12 and 16mm.Reinforcement design requirements are met (normally without compromise) and without any cutting or wastage on site.
Standard range Twin-leg U-bars and single leg hook-bars offered in standard reinforcement configurations and in fixed length casings.Speed of delivery.
Bending toolsBending ToolsSized to provide adequate leverage and to be a close fit around the reinforcement. A simple tool to ensure the best quality rebend on site.A safe method of straightening bars, which also helps to ensure straightness of reinforcement at joint interface.
To make an enquiry, email or or talk to us by calling 01844 266000.

A structural component, not an accessory

Continuity strip is sometimes regarded as an insignificant ‘accessory’ and brought into the UK without any recognisable form of approval. Such products tend to be entirely ‘standard’ in their configuration, with a ‘one size fits all’ approach to anchorage, lap and casing length. Frequently proving to be wasteful in application, these products offer little to address the needs of reinforcement design.

However, CARES approved continuity strip manufacturers are adept at the timely fabrication of their products, accommodating principal design and construction practicalities.

Varying reinforcement and casing dimensions to suit, results in what we know as ‘specials’. For UK CARES approved fabricators, these variations are simply incorporated and help to ensure that design intent is met, whilst also making life much easier for contractors.

Quality assurance and compliance

Reinforcement continuity strips are important structural components which require performance validation. CARES Technical Approval provides this validation through a process of structural testing, regular mechanical testing and audit. This meets the quality assurance needs of professional stakeholders and enables compliance with the National Structural Concrete Specification (NSCS) published by Construct Concrete Structures Group.

‘Specials are our standard’

For good reasons over 90% of FERBOX reinforcement continuity strip is made-to-measure, which has many efficiency advantages for concrete frame construction. Here’s our top 10:

  1. Removes the labour and associated costs of cutting and re-sealing cases (also compromising lap-lengths, which are cut short)
  2. No material losses: on a typical project, we estimate that 20% of ‘standard’ cases and reinforcement are wasted.
  3. Wastage transfer and disposal is eradicated, saving cost and protecting the environment.
  4. Correctly sized casing lengths eliminates the unplanned and expensive cost of remedial couplers, drilling and resin-fixing rebar.
  5. No need to run power and power-tools, which improves efficiency.
  6. Health and safety conditions are improved, since there is no need to use power-tools.
  7. Specified reinforcement design can normally be met (achieving correct anchorage, lap and concrete cover).
  8. In congested site working conditions, the hassle is taken out of installation by transferring avoidable operations offsite, into factory controlled conditions.
  9. Deliveries can be scheduled on a just-in-time basis, minimising site storage requirements and making the location-labelled FERBOX easy to find.
  10. Product performance requirements are met: All FERBOX manufacture is endorsed by CARES Technical Approval, helping you to meet the requirements of the National Structural Concrete Specification (NSCS).
Product Drawings
Enquiry Forms
Invisible Connections' Videos for connecting precast concrete elements using telescopic connectors
Seminar/webinar icon


Can't find what you're looking for? Our resources area provides much more information. Or get in touch.


Related projects

If you would like to discuss your specific project requirements, please contact us for technical advice without obligation.

Having FERBOX pre-sized is great from a quality and time-saving perspective, because if you use a regular continuity box, you end up having short lap lengths, depending on where you cut it. It goes back to your time spent fixing, looking for things, cutting them and having to retape corners and ends to stop concrete going in.

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

Invisible Connections are an outstanding company to work with. Between Ross in sales and Derek on the technical side of things, iC have an offering which the rest of the market would do well to get close to. I can’t credit these two individuals enough for the support they have given me for both standard and bespoke FERBOX connections – some rather more complex than others!

Iain Harding, Project Manager, Keltbray Structures 
Iain Harding, Project Manager, Keltbray Structures

We hadn’t typically gone the ‘specials’ route before. But, by investing a little upfront time to schedule our FERBOX requirements, we gained a smooth supply and installation process – without wastage or complication – and exceeded the programme demands of our slip-formed cores.

Adrian Paul, Project Manager, O’Keefe Construction (Greenwich) Ltd 
Adrian Paul, Project Manager, O’Keefe Construction (Greenwich) Ltd





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