Visible are the iron ties inserted ca. 1640 for stability.

The hospital (part of the former Cistercian abbey of Byloke or Bijloke) and its attached chapel form an L-shaped plan; the structures are joined by an integrated, twin-gabled façade at the west face. The chapel and a detached sick ward date from 14th to 16th century. The open-roofed infirmary of 11 bays is architecturally the most important timber structure at Byloke. The roof covers the ward (16 x 55 m). The masonry dates to 1228-1234 and occupies only 8 m of the overall height of 22 m. The walls (ca. 1 m thick) are buttressed at approximately 5 m intervals. Although considerable masonry support for the roof was designed, the walls have deflected outwards as a result of the combined roof thrust and shifting of the foundations; iron ties were inserted ca. 1640. The Byloke roof is a monumental two-tiered structure of steep pitch (ca. 60 degrees) forming a great trefoil arch. During an archaeological investigation of the site begun in 1990, the roof, whose date had been in question, was dated by dendrochronology with a felling date of AD 1251-1255.