LECKWITH Road bridge will remain closed until Friday, February 28, for resurfacing works to be completed.
Work began on the bridge on Monday and was scheduled to last for five days.
Dinas Powys councillor Chris Franks said that the works were necessary due to the poor condition of the bridge.
"Apparently the surface is rapidly deteriorating and the hot weather last year further weakened the surface when high temperatures caused the material to almost melt," he added.
"The work will not be a simple resurfacing. A depth of up to 400 mm (16 inches) will be removed and replaced with a more effective material.
"Due to the state of the bridge smaller vehicles will be used so as not to impose excessive loading on the structure."
Diversions will affect journeys on Cardiff Bus routes 95 and 95A.
From Barry to Penarth, buses will take the normal route to Leckwith Road Retail Park (ASDA) then travel via Hadfield Road, Penarth Road and Landough Hill to Landough Village (Penlan Road) and Llandough Hospital.
Buses will then continue normal route and times to Dinas Powys and Barry, 95, and Penarth, 95A.
Buses on these journeys will not serve Leckwith Village or bus stops in Llandough before Llandough Hill.
From Barry and Penarth, buses will operate the normal route to Cardiff Road (Merrie Harrier) then continue via Barry Road, Penarth Road and Hadfield Road to Leckwith Retail Park (ASDA) then back to normal route.
Buses on route 95 will not serve Llandough hospital towards Cardiff.
Journeys on route 95A will operate normal route to Llandough Hospital then return via Dochdwy road, Barry Road, Penarth Road, and Hadfield Road to Leckwith Retail Park (ASDA) then back to normal route.
A shuttle bus will operate, from 8am to 7pm each day, between Leckwith Village and Llandough Hospital and Merrie Harrier to connect with journeys on 95 for onward travel to Cardiff or Barry.
Passengers who board the the bus to Cardiff at Llandough Hospital can take route 95A which will operate as now, but return via the route stated to Cardiff.
Alternatively, use the shuttle bus and connect the 95 at the Merrie Harrier.