The Fallingwater Residence

Mill Run, Pennsylvania, USA

Project Abstract: Built in 1937, the Fallingwater Residence stands to this day as one of the greatest architectural achievements of Frank Lloyd Wright. Located in Mill Run, Penn., the home caters to thousands of visitors each year. Over time, the structure has endured a number of structural issues, which included cracking and deflection at the cantilever terraces. To ensure its historic value, contractors used post-tensioning systems to rehab a portion of the deteriorating elements. Post-tensioning allowed for hidden repairs in the floor cavity between the girders, making rehabilitation virtually invisible from many viewpoints. With repairs completed in 2002, the post-tensioned systems used proved to be a durable solution for the Fallingwater residence.

The Fallingwater ResidenceMill Run, Pennsylvania, USA

Project Overview: Originally built in 1937, the Fallingwater Residence in Mill Run, Penn., serves as a lasting embrace of architecture designed by Frank Lloyd Wright. Organic in the nature of design, the home has inspired American culture for more than 60 years. Over time, the structure has endured a number of structural issues, which included cracking and deflection at the cantilever terraces. Although the cantilever girders at the main level contain up to 16 one-inch-square bars each, engineers found that the girders were not capable of maintaining the design loads.

The Fallingwater ResidenceMill Run, Pennsylvania, USA

This inadequate load caused both terraces to sag downward towards a nearby stream.

The Fallingwater ResidenceMill Run, Pennsylvania, USA

Project Overview: The Western Pennsylvania Conservancy, owners of the property since 1963, began planning for rehabilitation of the deteriorating elements in 1995. Contractors utilized post-tensioning systems to limit the presence of restoration to visitors of the historical residence. Aesthetically, post-tensioning could be hidden in the floor cavity between the girders, making rehabilitation virtually invisible from many viewpoints. Four concrete cantilever girders were used to support the main terrace, with a concrete slab placed

monolithically at the bottom of the girders to form a soffit. Contractors also used multi-strand post-tensioning of three support girders spanning in the north-south direction. Thirteen-strand tendons were placed on each side of two of the girders. One 10-strand tendon was placed on the western side of the third girder. Eight monostrand tendons were slated for the east-west direction.

The Fallingwater ResidenceMill Run, Pennsylvania, USA

Project Overview: The project was a challenge for contractors for several reasons including the fact that it was imperative to preserve the historical elements of the structure. Additionally, contractors had to work in cold weather conditions to complete the project within budget and in a timely manner. With repairs completed in 2002, the post-tensioned systems used proved to be a success for contractors of the Fallingwater residence. The durability of post-tensioned concrete will allow for the long-term sustainability of Frank Lloyd Wright’s iconic home.