Drymen Bridge carries the A811 across the Endrick Water a little to the south of Drymen, and just to the north of the TOTSO junction between the A809 and A811.
The bridge consists of 5 arches in the local red sandstone. Only two of the arches cross the river, the central one and that to the south of centre, the remaining three being flood arches. The bridge is built of regular blocks, shaped like rubble, with ashlar arch rings and a cornice line at road level. The central arch is further embellished by being flanked with semi circular piers rising from the cutwaters, suggesting that originally it may have been the only arch to span the water.
The bridge seems to have been originally built in 1765 with a 'major reconstruction' in 1929. This section of the A811 was originally built in the late 1750s or early 1760s as one of the last military roads built by Major Caulfeild, however the bridge is too decorative for a military structure. The answer, however, lies nearby in the Buchanan Estate which was the former home of the Dukes of Montrose. It seems possible that they funded the decoration, if not the whole bridge, as there was a lot of work done on the estate at that time.
A short distance to the south of the bridge, the A811 meets the A809 at a TOTSO junction, where the main route is the A811-A809 route between Drymen and Glasgow This route runs north - south, with the A811 also heading west to Balloch on Loch Lomond. The junction is a simple T junction, where the once wide bell on the A811 has been reduced with large patches of red paint to restrict the space available for traffic turning out.