After spending more than $23 million dollars and experiencing two delays, the finish line is finally in sight for the restoration of Frank Lloyd Wright’s Unity Temple in Oak Park, Illinois. Built for a Unitarian Universalist congregation between 1905 and 1908, the poured-in-place concrete structure is considered by many—including Wright himself—to be the architect’s most notable contribution to modern design.

The multi-phase plan to repair the National Historic Landmark and UNESCO World Heritage Site had been in discussion for many years prior to work finally starting in the spring of 2015. Originally expected to be competed by the fall of 2016, the timeline later slipped to late March of this year. According to the Unity Temple Restoration Foundation, the most recent estimate anticipates a public unveiling to take place in July.

The scope of the work involves a multitude of structural improvements such as a full restoration of the building’s exterior including the majority of the temple’s roof. Inside, the structure’s striking original skylights, windows, light fixtures, flooring, plastering, and millwork are also in the process of being painstakingly brought back to their former grandeur. Additionally, workers will modernize the building’s mechanical systems and add air conditioning.

Phase I: Strengthening the Structure

• Restoration of the concrete walls, chimney, and roof slabs

• Restoration of art glass laylights and skylights

• Restoration of elevated terraces, east retaining wall, and ornamental planters

• Development of routine maintenance procedures to monitor concrete for future cracks and deterioration

• Development of appropriate repair process to prevent water from penetrating the surface and causing new damage

Phase II: Achieving Climate Control

• Installation of state-of-the-art geothermal ground source heat pump to stabilize temperature and humidity levels year-round

• Air-conditioning for the warmer summer months

• Aid in preventing future structural and surface deterioration

• Upgrades to mechanical, electrical, plumbing, and life safety systems

Phase III: Restoring the Interior

• Restoration and conservation of all interior art glass, plasterwork, paint finishes, concrete floors, Magnesite floors, art glass lighting fixtures, and oak trim

• Interior surfaces restored to original texture, color, and translucence

• Removing all over-painting and applying replicated new finishes

• Applying new layer of plaster with replicated finishes

• New over-painting on all existing surfaces to resemble original treatments