Complex sentence: Based upon tree-ring dating, construction continued through 1128, but in the materials and techniques of construction in the 1100s was less reliable and methodical, using poorer quality adobe and rock, that resulted in irregular shaped rooms.
Split into simpler sentences: Based upon tree-ring dating, construction continued through 1128. Construction materials and techniques in the 1100s were less reliable and methodical, with poorer quality adobe and rock, that resulted in irregular shaped rooms.