Timber bridge

Most 12th-century bridges were built of timber: a deck of planks carried on piers of driven oak piles, sometimes on stone footings. They needed constant repair and were easily swept away by floods or fire. London's bridge over the Thames was of timber until Peter of Colechurch began a stone replacement in 1176, completed in 1209. Tolls and pious bequests paid for upkeep.

Sources: britannica.com