Cost-Saving, Timely, and Light: How Filigree Wideslab Works for Philly

For nearly 40 years the world of concrete construction has utilized a system known as Filigree Wideslab. Filigree, fabricated by Mid-States Filigree, is a pre-fabricated thin prestressed concrete slab used in conjunction with field cast concrete for a finished concrete slab. The method gained popularity in the 1980s when many Atlantic City casino towers were looking for a way to build cost efficiently and quickly.

The Filigree system saves on form work because the factory-made precast shell is the project’s formwork. These precast shells are made using a smooth metal formed system in eight-foot wide planks. The system incorporates styrofoam voids that are set in the shell. This helps lighten the slab in its final form. The smooth surface is a major benefit to the Filigree system and the joints can either be exposed or covered up- depending on the needs of the project. Overall, the precast shells reduce forming requirements thus potentially saving labor in the field, which is key for the Philadelphia construction market.

To determine whether a new project will benefit from the Filigree System, The Harman Group begins the process by performing a structural systems study. During the system study the contractor and management team are given several structural systems. They then select the best system for the project.

The Harman Group has used the Filigree wide slab method in many Philadelphia area projects. The Granary was one of the more well-known projects where this system was used. Just completed in 2017, the Bridge, an 18-story mixed use concrete tower also utilizes Filigree.

The Harman Group also utilized the J Filigree system for the St. Barnabas Medical Center in Livingston, New Jersey. The 240,000-square foot west wing addition to the Cooperman Family Pavilion added an outpatient surgery suite, private inpatient bed units, an expansion to the current NICU unit, a new central administration area, a public atrium, and associated campus upgrades. The new west wing of the hospital was constructed with a thin concrete filigree and drop beam structural system, which allowed for a slim structural depth. This is a departure from traditional methods used in hospital construction, which often call for a more traditional structural system like composite steel and slab on metal deck. The Filigree method was chosen in order to match the existing hospital floor elevations with a thin structural system yet maintaining a long span between columns.

St. Barnabas Medical Center also added a four-level, open, precast parking structure with 400 spaces as part of the project.

As the building boom continues in Philadelphia and the surrounding area, The Filigree method continues to be selected for a light, thin, cost effective structural system.

By Janis Vacca