Helical restoration for historic skyscraper

With construction beginning in March 2011 and a Grand Opening slated for September 2012, significant budget concerns existed over the methods of repair to the exterior restoration in order to properly preserve and enhance the building’s core. Notably, the deteriorating exterior limestone corners of the building would have to be completely replaced at great cost. To make the numbers work, Akins Construction enlisted leading industrial masonry repair reinforcement system manufacturer Helifix®, Inc. (Streetsboro, OH) to implement its’ patented DryFix remedial pinning and tying system to reconnect, stabilize, and provide retrofit strengthening to the existing damaged limestone corners for all 34 floors.

Cornerstone Problem

During the projects’ initial inspection, at least two large pieces of limestone corners had fallen from the 18th floor during a storm due to rusted anchoring and freeze/thaw water damage. The historic style and age of the building’s expansion joints in the corner limestone columns, where major ‘sway’ movement occurs, made the need to remove and replace the limestone corners on all 34 floors of the historic tower seem imminent.

Given the project’s economical budget restraints, other methods of repair were explored and Akins Construction contacted Helifix, whom they had used over the years for creative applications, to provide an alternative solution to replacing the large volume of loose terracotta and limestone on the building’s deep corners. Helifix recommended its DryFix Remedial Tying system that offered the following solution that was quickly approved by JC Beal and Kramer Design.

Cornerstone Solution

Developed by Helifix over many years, the patented DryFix Remedial Tying System is an extremely versatile and reliable remedial pinning and tying system. Quick and easy to install, it provides an effective and economical stress-free connection between all commonly used building materials in both cavity and solid masonry constructions without needing any special grouts, resins, or mechanical expansion.

DryFix remedial ties, together with their associated installation techniques and high performance Helifix grouts, produce secure connections with brickwork, CMU blocks, stonework, concrete, marble, limestone, travertine, terracotta and timber. The system is embedded within the existing masonry to be fully concealed once installed. Because it’s generally installed into the existing masonry; expensive and time consuming tear down and rebuild are avoided while retaining the visual aesthetics of the structure−which made the system ideal for The Broderick Tower exterior restoration project.

The slim profile DryFix remedial ties are precision engineered from 10mm austenitic grade (304) stainless steel. The formed stainless steel wires offer a typical 0.2% proof stress of 500N/mm², but after the cold forming manufacturing process that creates the helical hi-fin design, this more than doubles to around 1100N/mm². This means that with its relatively small diameter, the system provides substantial tensile properties to the masonry.

Additionally, DryFix ties may be used in hollow materials and close to edges. They are sufficiently flexible to permit normal masonry movement, are designed to shed water in cavity construction, and provide strong, reliable axial restraint in both tension and compression.

Cornerstone Installation

In the case of Broderick Tower, Helifix delivered the DryFix materials within 24 hours of approval and remained onsite to assist Akins Construction during the installation process. A variety of lengths and sizes (10”-15”) of DryFix remedial ties were utilized to secure the loose terracotta and limestone on all four corners of the building’s 34 floors; in addition to various re-anchoring throughout the rest of the building.

Installation involved the simple power-driving of approximately 4-6 DryFix anchor ties per corner stone into position via a small pilot hole and using a special installation tool that leaves the end of the tie recessed below the outer face to allow an ‘invisible’ finish. Since there was no sound ‘back-up’ anchor stone available, the ties were anchored into adjacent limestone corners on each side for an optimal structural repair. High performance Helifix polymer grout was also used in key areas tohelp increase the bond.

Cornerstone Conclusion/Results

Helifix’s concealed, non-disruptive DryFix remedial tying system is on track for completion of The Broderick Tower’s Grand Opening in September 2012. Notably, there was no need to remove any of the limestone corner columns and ensuing pull-tests conducted on completed installations indicate optimal flexibility and movement during ‘sway’ as the stones stay securely anchored.

According to Akins Construction Owner Rich Akins, “Other methods were explored to remove the limestone completely with new anchors to the back-up walls. Ultimately, Helifix’s DryFix solution provided the ability to restore rather than replace the limestone corners and saved Motown Construction Partners upwards of approximately $1 million to the project’s exterior restoration budget.”