Archaeologists and building researchers in southern Germany have discovered that a medieval cellar ceiling was built with timbers from a ship, including a remarkably complete section of its hull.
The find was made in Konradigasse in Konstanz, on Lake Constance. Researchers from the State Office for the Preservation of Historical Monuments, or LAD, date the cellar to 1244. The discovery offers rare evidence of material reuse and new clues about medieval shipbuilding.
Dr. Aline Kottmann, a medieval archaeology specialist at the LAD, said researchers initially knew only that the planks had been reused. Discovering that they had once formed part of a ship came as a complete surprise.
The ceiling covers more than 25 square meters (269 square feet) and contains at least 19 ship planks. Wooden pegs, rows of pegs and characteristic plank shapes helped researchers identify their maritime origin.
Medieval ship timbers found a second use
Alexandra Ulisch, a member of the LAD’s “Wrecks and Deep Sea” project, said medieval builders were already known to have reused decommissioned ships. The project has previously identified 31 unknown shipwrecks in Lake Constance during a systematic survey of the lake’s submerged heritage.
The scale of the Konstanz find, however, makes it unusual. Ulisch explained that here, not just individual fragments, but an almost completely intact ship’s hull was used.
Archaeologists in Germany made a remarkable discovery inside a medieval cellar: ship timbers dating back more than 700 years. At least 19 planks from a medieval cargo vessel were reused to build a cellar ceiling in Konstanz in 1244. pic.twitter.com/pKD4cnp450
— Tom Marvolo Riddle (@tom_riddle2025) August 17, 2026
Initial analysis suggests the timbers came from a flat-bottomed sailing cargo ship. Its construction is comparable to other medieval finds from Lake Constance, including the 14th-century wreck at Kippenhorn near Immenstaad.
Other recent discoveries have also provided rare evidence of medieval cargo-ship construction, including a 600-year-old cargo vessel found beneath the Øresund Strait.
Researchers are also examining whether parts of the ship’s side planking survived. Such remains could reveal how medieval shipbuilders connected a vessel’s flat bottom to its sides.
Repairs reveal medieval shipbuilding techniques
The timbers preserve at least four repairs made during the vessel’s working life. Shipbuilders cut out damaged sections and replaced them with precisely fitted wooden inserts. One repair features a dovetail-shaped inlay with no known direct parallel in medieval shipbuilding on Lake Constance.
Some planks remain connected as they were aboard the ship. Caulking used to seal gaps between them has also survived in places. Researchers have analyzed the material for further evidence about medieval construction techniques.
Similar studies of preserved ship coatings have shown how such materials can reveal details about ancient shipbuilding and repair methods.
The preservation is particularly valuable because the few known medieval shipwrecks in Lake Constance remain underwater and are difficult to examine. The Konradigasse timbers are far more accessible to researchers.
Researchers build a 3D record
Researchers documented the ceiling again in mid-August 2026 using structure-from-motion, or SfM. Hundreds of photographs are being combined to create a three-dimensional digital model of the remains.
The team also collected samples for dendrochronological analysis. Tree-ring patterns could reveal when the timber was cut and provide more information about the vessel before its wood was reused in the cellar. The same dating method has helped researchers refine the chronology of a Bronze Age palace in Greece.
The find goes far beyond a chance discovery, Kottmann explained. It is a valuable testament to medieval shipbuilding technology and of particular importance for the maritime archaeology of the Lake Constance region.
Researchers said the findings remain preliminary. Further details are expected after the ongoing analyses are completed.
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