New 'M' building roof was built within its walls

Elwood, Ill.
August 11, 2010

When chemical manufacturer Stepan decided it was time to replace the 24,000-sf roof of the "M" Building at its Elwood, Ill., facility, the A/E firm chosen for the job, Ambitech Engineering, quickly learned how difficult the task would be.

A survey of the nearly 50-year-old wooden bow-string truss roof revealed cracking in many of the trusses, and planks and purlins were rotting, to the point where the roof was in danger of collapse. Reacting quickly, Ambitech, of Downers Grove, Ill., installed temporary beams to support the roof until a new one could be designed and constructed.

Ambitech and general contractor Graycor Industrial Construction, Homewood, Ill., initially thought it best to erect the new steel beams for the roof outside the existing facility, thereby keeping production interruptions to a minimum.

They had to shelve this strategy, however, because one side of the building housed a loading dock and rail line that could not be obstructed, and the other side had underground sewer lines whose exact location was unknown. Moreover, putting the columns on the exterior would have increased the plant's floor area to the point where additional permits would have been required.

Instead, the team decided to build the new roof columns inside the existing walls and run the 200-foot main steel beams along the long span of the building. This reduced the total amount of equipment, vessels, piping, and conduit relocations, saving Stepan about $500,000.

Similarly, the original plan for the north row of main support columns was adjusted to prevent the costly permanent relocation of two 12,000-gallon vessels and the risk involved in digging near a 40-year-old well water line.

In the midst of the project, Stepan asked the architects and engineers to raise the roof's elevation by 30 feet. This meant changing the foundation design and column sizing to handle increased wind loading and other factors.

Steel erection for the $8.5 million project began at the end of the summer of 2004, but to be able to enclose the building before the cold weather set in, the crew kicked into a 58-hour work week. The building was largely enclosed by November 2004, with final completion taking place last January, three months ahead of schedule.

"Raising a roof of an existing manufacturing facility while it remains in operation 24 hours a day is commendable," said judge William Bast, PE, SE, SVP, Thornton-Tomasetti Group, Chicago.

Although chemical production continued all the while, now it is being done in a much safer, brighter environment. For this effort, the project earned Special Recognition honors in BD&C's 22nd annual Reconstruction & Renovation Awards.