Inclinometer readings of a deep excavation project are presented in this paper to show that joint details could have significant effects on the behavior of cross/buttress walls. It is found that both T-shaped and clean contact joints are capable of limiting the lateral displacement of perimeter diaphragm wall to less than 10 mm in this case. On the other hand, a soft contact joint nullifies the restraining effect of buttress wall, resulting in a maximum wall displacement of about 30 mm for this 12 m deep excavation.