Motorists warned of disruptions this weekend as 50-year-old bridge undergoes critical repairs

The structures between Junction 12 and Hilsea Interchange require extensive repairs to their surfaces and waterproofing systems, with National Highways now having to act.

To allow the agency to complete the work, four complete weekend shutdowns will take place across September and October.

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The first closure will take place this weekend, with motorists travelling westbound encountering closures at the Portsbridge roundabout from 9pm on Friday, September 5, until 6am on Monday, September 8.

A second westbound weekend shutdown will take place from 9pm on Friday, September 26, through to 6am on Monday, September 29.

For drivers heading eastbound, Junction 12 will be closed from 9pm on Friday, October 10, until 6am on Monday, October 13. The final scheduled closure affects the same eastbound section from 9pm on Friday, October 17, to 6am on Monday, October 20.

The bridges, locally referred to as the IBM bridges, have suffered considerable degradation since their construction in 1975.

National Highways explained that water damage to the concrete has sparked the need for a comprehensive repair programme.

Initial work on the bridge has been taking place all year, with the agency explaining that work beneath the structures is nearly finished, with crews now preparing to tackle the bridge decks themselves during the planned closures.

National Highways said it has also built in contingency weekends, should weather conditions prevent the scheduled work from proceeding.

Additional overnight closures will follow to complete the installation of new bridge joints once the main surface work concludes.

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The 50-year-old structures have experienced significant deterioration, with corrosion affecting the steel reinforcements within the bridges over the years.

Recent months have seen contractors complete substantial concrete repairs to the undersides of both bridges. Protective coatings have also been applied to prevent further steel corrosion. The scale of these repairs required single-lane closures on each bridge while the concrete was being addressed.

With the underside work approaching completion, attention has now turned to the bridge surfaces. The upcoming weekend closures will enable contractors to strip away the existing road surface and remove the deteriorated waterproofing that has allowed water to seep into the structure.

Emma Weston, project manager at National Highways, said: "Our workforce has made great progress and ensured that everything has gone to plan, often under arduous conditions, during the recent heatwave."

The forthcoming work presents particular challenges, including the safe removal of asbestos discovered within the old waterproofing materials. Specialist contractors have been deployed to handle the hazardous material disposal before new waterproofing can be installed.

She added: "The next phase of work will involve removing the surfacing and age-expired waterproofing on the top of the bridges and upgrading the existing surface drainage. We've got an additional challenge to remove the asbestos from the waterproofing.

"It will be safely removed and disposed of by specialist contractors before the new waterproofing layer is applied and new surfacing laid.

"We understand the frustration our work may have caused. The weekend closures have been carefully planned to avoid the Portsmouth Football Club home and away games, as we know these would be busier weekends."