The Spark Central Complex is the largest commercial development in recent years in the Wellington CBD, the development achieved a NZGBC 5 Green Star rating.

On completion of the project in 2011, it delivers 19,000 m2 of open plan style office accommodation. The complex consists of two structurally separate buildings: the Willis and Boulcott Towers, 12 and 14 story high respectively, with a 12 story high atrium between the two towers. The Willis Tower is an extension to the existing Airways House with retention of the heritage Tisdalls facade. Extensive strengthening work was carried out on the Willis Tower using FRP, with additional shear walls incorporating permanent ground anchors, and structural skin installed behind the historic facade. Clendon Burns & Park Ltd is responsible for the design of all the civil & structural engineering work associated with this prestigious commercial development.