Unreinforced masonry buildings (URM) form a significant and rapidly diminishing part of New Zealand’s collective heritage and there is a growing concern that appropriate retrofit repair and reinforcement steps be taken to preserve these structures for future generations (1).
In Auckland, threats to the longevity of URM structures include salt, wind and seismic loading. Using a range of Helifix remedial systems, structural integrity was re-introduced into this building, situated in central Auckland, and strength added in anticipation of future seismic events. The original construction materials and character were retained through the use of non-disruptive Helifix installation techniques.
The deterioration of the façade included corroded wall ties, failed lintels, cracked, bowed and unstable brickwork.
The Helifix repair scheme involved installing HeliBar stainless steel reinforcing bars into channelled-out mortar beds at various levels and locations along the façade. These tied the masonry together, stitched cracks, and formed masonry beams that reinforced the structure and spread the loads.
A suitably coloured repointing mix was used to cover the slots and completely conceal the location of the installed bars.
StarTies were used to connect sections of the external brickwork leaf that needed to be reset back to the internal leaf. In these instances, undersize, 5mm pilot holes were drilled 70mm deep into the internal leaf before 8mm diameter StarTies were driven into position and their exposed tails bonded into the mortar beds of the newly constructed external leaf section. DryFix ties were used to tie all other areas of the facade back to the internal leaf. To minimise damage to the existing brickwork, small rotary percussion drills holding straight-shanked 5mm diameter drill bits were used to drill the pilot holes necessary for DryFix installation. Holes were drilled through the external leaf and 70mm deep into the remote leaf. DryFix ties were then installed using a Power Driver Attachment fitted to a light-weight SDS drill. A coloured patching mortar mix was used to patch all DryFix entry points to leave a near invisible repair.