It seemed that the oyster shells in "Keke Cuo" were not selected by size or by following any rules, but it was found after careful analysis that the big shells were laid in stretcher bond (the overlap, which is usually of half the length of the object) whereas the small ones were laid in bull header bond (the overlap, which is usually of half the of width of the object).
From inside to outside, the walls of "Keke Cuo" in Quanzhou are made up of 15 mm facing oyster shell mortar, 25 mm leveling mortar mixed with straw, 300-400 mm internal wall infilled with brick and rock debris, 30 mm rendering oyster shell mortar and 70-80 mm oyster shells laid in stretcher or bull header bond.
