Remedial wall tie programme secures timber framed properties

In Headlands Drive, Aldbrough, 10 semi-detached two storey properties owned by the local authority were found to have horizontal cracking in their mortar joints when surveyed prior to receiving external wall insulation. Further inspection revealed that remedial ties had been installed previously but the contractor had not isolated the original failed wall ties, which had continued to corrode and expand, causing the bed joint cracking.

Unusually for properties built in this area in the 1960’s, the houses were of timber frame construction and had ‘L’ shaped fish tail ties. An increased tie density was required, with the new remedial ties both ensuring a secure connection between the brick outer leaf and the timber stud and increasing the load bearing capability of the wall to take the additional weight of the new external cladding.

The Helifix solution

A remedial wall tie programme was devised using Helifix stainless steel RetroTies. As no records existed of the existing tie density, and based on building height, exposure and loadings, the new remedial ties were to be installed at 2.5 fixings per m².

The first task was to locate the corroded ties and isolate them by fitting suitable isolation sleeves or by cutting them back the tie where it was deemed appropriate and the action would not disturb the internal plasterboard finish.

Next, the exact location of the timber stud had to be established. The contractor carefully removed selected bricks to identify stud positions and, after identifying the stud centres, proceeded to drill the required 12mm clearance holes in the masonry for the tie installations.

RetroTies, 8mm x 195mm, were inserted through the holes and driven into the internal studwork, as they are self-tapping, with a minimum embedment of 50mm. The outer end of each tie was then bonded into the external masonry using PolyPlus resin with approximately 160 RetroTies installed on each property.

With all necessary repointing completed, East Riding Council was pleased with the final results having chosen Helifix based on price and quality but also because they were able to provide design guidance, proven products and techniques and quality of installation through the use of an Approved Installer.