How to identify wall tie failure in high rise buildings

Wall ties are used to connect the inner and outer wythes of cavity constructed walls and this type of cavity wall construction is commonplace in the US.  Successful  solutions are available to repair the wall without having to rebuild the entire outer wythe which in the past has caused a wide range of secondary problems.

Common wall tie failure indicators include:

•    Horizontal cracking
•    Out of plumb, bowed, cracked or collapsed brickwork elevations
•    Rust staining on the walls
•    Problems having been identified within properties of a similar age and location

Wall ties are essential to the stability of the normally unloaded outer wythe.  The outer wythe can be affected by either direct wind forces, or more commonly wind suction forces – particularly within high rise buildings. Where insufficient or perhaps incorrect wall ties have been installed, or where the corrosion of the existing ties has been identified, then remedial wall ties will need to be installed to prevent potentially catastrophic failure.

The majority of corrosion of wall ties takes place in the outer wythe bed joint. This can lead to considerable horizontal cracking, and cumulative raising of the outer wythe.   Smaller ‘wire’ ties do not usually have sufficient corrosion product volume to crack the brickwork. Ongoing cracking is a certain indicator that new ties should be installed, and the existing either removed or isolated. In the case of ‘wire’ ties the lack of cracking will not necessarily reduce the necessity for new wall ties.

Developed by Helifix®, Inc. over many years, the patented DryFix Remedial Pinning and Tying System provides an effective, economical, and stress-free retrofit connection between all commonly used building materials. The slim profile, precision engineered DryFix helical ties (stainless steel; grade 304 or 316) are made from a drawn stainless steel manufacturing process that creates the helical hi-fin design that more than doubles the proof stress. With its’ relatively small diameter, the system provides substantial tensile properties to the concrete.

Ideal for both cavity and solid masonry constructions, the DryFix system requires no special grouts, resins, or mechanical expansion, and is embedded within the existing masonry to be fully concealed−once installed.

DryFix installation involves simple power-driving of the precision engineered, slim profile remedial ties into position via a small pilot hole. A special installation tool is then used to leave the end of the tie recessed below the outer face to allow an ‘invisible’ finish. High performance Helifix polymer grout was utilized in key areas to help increase the bond.

DryFix systems are installed into the existing masonry; expensive and time consuming tear down and rebuild were avoided while retaining the visual aesthetics of the structure.

The DryFix Tie was specified as the ideal solution for the Lancaster Leaf Tobacco Company’s structural warehouse restoration project, where approximately 6,400 DryFix helical anchor ties were used throughout key focus areas of the tobacco warehouse’s north, south, and west elevations. You can view this project and many others, by visiting our case studies section. Click here.