An hour before sunrise Sept. 28, more than 30 carpenters, masons and laborers started a 12-hour continuous pour to form Paul Milstein Hall's concrete dome.

The dome is a signature feature of the Rem Koolhaas-designed building for the College of Architecture, Art and Planning. The quality and consistency of the pour was critical because the dome's entire underside will be the ceiling for a critique space for AAP students' work.

The engineering that went into planning for the pour was equally as important, as the completed dome will weigh approximately 900,000 pounds -- or about 175 pounds per square foot.

To get the 200 yards of concrete flowing, one pump truck and two conveyor rigs, on different corners of the building, poured the low-viscosity material from the top. Tradesmen crawled on the structure, moving the concrete into place with vibratory tools to help ensure a smooth surface on the bottom and used hand floats to smooth the top. The layer they poured is the bottom half of what will be a double shell, with a layer of insulation and utilities sandwiched between.

Workers have been on site since June to prepare for the pour, building wooden falsework to establish the dome's shape and provide support. On top of the falsework, plywood sheathing was installed and precisely caulked to keep the surface smooth. Woven on top of the wooden form, approximately 71.5 tons of reinforcing steel rebar was put in place. Workers will begin to remove the forms for the dome about two weeks after the pour, depending on weather conditions. Utilities and insulation will begin to be installed in about four weeks.

Pike Co. of Rochester, N.Y., is the subcontractor handling the dome pour and other concrete for the building. Welliver McGuire of Montour Falls, N.Y., is the construction manager on the project. Paul Milstein Hall was designed by Koolhaas and the Office for Metropolitan Architecture's New York City office. Engineering consultation for the building's cantilevers and the dome was done by Robert Silman Associates, headed by Robert Silman '56.

Aaron Goldweber is communications director in the College of Architecture, Art and Planning.