Failure of Existing Wall Ties

ASRS were contacted by a residential client who suspected cavity wall tie corrosion to their two storey end-terraced property. ASRS inspected the condition of the existing cavity wall ties and associated defects. With the use of a metal detector a number of existing wall ties were located. Due to the presence of cavity wall insulation, we were unable carry out an endoscope inspection. Therefore, as agreed with the client, we carried out an intrusive investigation to the front and side of the property, by means of locating an existing tie and removing the mortar around it, to expose the wall tie. We were then able to investigate its condition, which revealed oxidization and rusting to the ties. Rusting causes wall ties to expand, which generally results in horizontal cracking along the bed joint We were unable to inspect the wall ties to the rear elevation due to the presence of a conservatory. However, horizontal cracking was noted above the first floor window heads.

The Problem

In view of our observations it was assessed that the existing wall ties were significantly affected by varying stages of corrosion. The corrosion of existing wall ties will affect the structure of the building and make it vulnerable to progressive failure unless the ties are isolated. Failure to address the issue could result in the collapse of the outer wall where it becomes detached from the inner.

The Solution

We recommended the installation of remedial Helifix Dry Fix wall ties. Using a metal detector we located and marked up all existing wall ties for isolation. Helical wall ties are made from stainless steel, therefore they do not rust. A pilot holes is drilled and the wall ties are then hammer drilled into both the outer and inner leaves, tying them together. Our team of approved installers installed new remedial Helifix Dry Fix wall ties to the front, flank and rear elevations. They were installed at 900mm centres horizontally, 450mm vertically, with additional ties at 300mm vertical centres within 225mm of openings. Following the installation of the new remedial Helifix Dry Fix wall ties we isolated the existing wall ties to ensure no further oxidisation would occur.

Completed Project

Once all new remedial Helifix Dry Fix wall ties had been installed and existing ties had been isolated we made good all areas of mortar disturbed by our installation, the mortar colour was matched as near as practicable leaving an aesthetically pleasing finish for the client. All work was completed in 3 working days and within budget. We also provided a 25 year Helifix indemnified guarantee.