With Croydon Flyover in need of joint replacement, Metrail employed a bespoke planing drum and Permatrack H, replacing a total of 33 joints whilst keeping road closure times for the works strictly to schedule – 9 pm until 5 am.

  • Challenge
  • Solution approach
  • Technology

  • Execution

  • Result

The challenge

A little background info about Croydon Flyover: as the name suggests, it’s an overpass in Croydon, England that was opened in 1969. And with Croydon Flyover prone to heavy traffic congestion, queuing traffic ends up sitting on top of the bridge, which places huge amounts of pressure on the expansion joints in the structure.

Facts & Figures

March 2019

Croydon Flyover, part of the A232

IKO Permatrack Heavy Duty Expansion Joints

Solution approach

Early Contractor Involvement (ECI) with the PC Kier and the client allowed us to come up with a more heavy-duty solution for the joints as well as minimise the risk to delivery whilst maximising the working window and ensuring minimum delays to the road user. During the project, the depths of the joints were not as stated in the as-builts. But from experience we always ensure we carry a percentage uplift of material to allow for the unknowns – like this one!

Technology & Execution

For this project, Metrail replaced a total of 33 joints using Permatrack H, which was delivered hot charged in tankers carrying up to 18 tonnes of material direct to site – this increases safety for Metrail’s teams handling the material as they do not have to prepare it on-site, and it also allows for greater speed of application, thus saving on traffic management costs.

How much Permatrack H was used on this project?

In total: 54 tonnes. The high-modulus joints incorporate Permatrack PSB, which is a highly polymerised elastic bituminous membrane in preformed strips. These strips provide the movement properties of the joint and are bonded to Permatrack H using a high-modulus matrix consisting of SBS modified bitumen and Trinidad Lake Asphalt. As far as the movement range goes, the joint material caters for +/- 20mm (40mm total), and this movement range is in line with the recommendations of CD357 issued by Highways England. Our use of a bespoke planing drum gave us full control of the works and allowed us to amend the works as needed on-site. Using it also saved time compared to conventional removal of the joints with handheld vibrating breaker tools. The material that was planed out was taken off-site and disposed of correctly and waste certificates issued.


Early contract involvement on this project added value through achieving programme certainty and specialist input into appropriate intervention solutions as well as mitigating delivery and safety risks. We’re pleased to report that the combination of exceptional products and our effective project management made the project a great success delivered on time and on budget.

This project demonstrates Metrail’s ability to work in restricted nighttime only windows with critical carriageway reopening times always achieved.

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