The tradition of building with clay in Germany and Northern Europe is that of half-timbered construction. For infill, straw clay was usually used, a plastic mixture of clay with stabilizing straw, applied in countless regional variations. New interest in the building material clay has led to significant uncertainties in practice, as attempts to replicate the historical model reveal that the living tradition of clay techniques has been interrupted, leaving reliance on information found in literature. The composition of the clay alone is not what matters in infill; its quality is primarily determined by the application technique. During the restoration and conversion of the Gothic House Römer 2-6 in Limburg, its straw clay infill from different eras - from the 13th to the 18th century - could be systematically examined.