The possibility that buildings in the Nara period onwards might have been kokera (bark tiles)-roofed or bark-roofed has been investigated; but restorations of the roofs of pit dwellings from Yayoi or earlier periods ruins (for example, Toro Ruins) are usually thatched.
奈良時代以降の場合はこけら葺や樹皮葺であった可能性が検討されるが、弥生時代以前の遺跡（登呂遺跡など）で復元される竪穴式住居などの屋根は通常茅葺とされる。