Unreinforced masonry (URM) buildings 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 facade 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 facade. 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.

1. Goodwin C., Tonks G. and J. Ingham (2009). Identifying heritage value in URM buildings. URL: retrofitsolutions.org.nz (Accessed: March 2010)

Architect Harry Seidler considered Blues Point Tower to be one of his best buildings,1 and his many admirers would no doubt agree. But following its completion in 1962, Blues Point Tower has attracted more than just devotees. Salt, moisture and exposure to Sydney's harbour environment have all exacted a toll on the building's facade.

The building comprises a concrete frame structure and cavity brick infill panels. Weathering and building movement have contributed to the development of a number of problems requiring remediation including masonry cracking and corrosion of the original wall tie system. In 2000, two Helifix repair schemes were called upon to help with works conducted to repair the building's southern elevation. DryFix ties were used to reconnect the external and internal brickwork leaves of each infill panel while RetroTies were used to connect the edges of each panel to the surrounding concrete superstructure.

To install the DryFix, small undersize holes were first drilled through the external leaf and into the internal leaf. DryFix ties were then driven in to finish just below the surface of the near leaf using a Power Driver Attachment. To install the RetroTies, pilot holes were drilled through the brick and into the concrete behind before the holes in the near leaf were enlarged to 10mm. RetroTies, 8mm diameter, were then power driven into the pilot hole in the concrete to create a mechanical connection. Finally, resin was injected into the clearance hole to chemically bond the exposed end of the tie to the near leaf masonry. RetroTies were used in preference to DryFix in this instance to accommodate differences in the densities and structural performance of the materials involved.

Tests conducted recently to assess the performance of these remedial wall tie systems confirm that both continue to provide structural security after nearly 10 years of continuous service.

The results indicate the strong, on-going performance of the resin bond into the near leaf of the RetroTies and the strong, continuing mechanical performance of the DryFix and RetroTie connections into the internal brickwork and concrete columns respectively.

A new round of work organised to repair the remaining three elevations is now under way, and following the successful demonstration of the long term performance of the original Helifix repair programme, DryFix and RetroTies are again part of the remedial schedule. By completion, several thousand DryFix and RetroTies will have been installed by teams of experienced installers working off swinging stages.

1. Lacey S. (2002). Towering Ambition. Sydney Morning Herald, September 28.

A collaborative project investigating the seismic retrofitting of masonry buildings, involving researchers from both sides of the Tasman, continues to make headway. Led by engineers at the Universities of Auckland and Canterbury in New Zealand, in conjunction with colleagues at the Universities of Newcastle and Adelaide in Australia, the Seismic Retrofit Solutions project has targeted the development of cost-effective guidelines and solutions to retrofit unreinforced masonry (URM) structures.

The wording and implementation of a full list of solutions and formal provisions has yet to reach fruition, but the research, which is now at an advanced stage, has produced compelling results and there is a growing expectation that a suite of technical seismic manuals will result. As part of the project, researchers have investigated the performance of a number of different retrofitting systems. Shotcrete, fibre-reinforced polymer (FRP) sheeting and shear truss systems, among others, have received attention. Helifix has also supported a coordinated series of studies into its own Helibeam System of masonry reinforcement.

Unreinforced masonry panels, cut from condemned buildings in Gisborne, the site of a significant earthquake in 2007, provided the raw material for Helifix testing in New Zealand. In Australia, tests conducted using newly constructed masonry panels reinforced with HeliBar and HeliBond grout have fueled research at the University of Newcastle.

Results to the date of publication (November 2009) confirm much of what is already known about the Helibeam System, and which has been confirmed previously at numerous different sites and laboratories around the world. And that is: the Helibeam System can be used to provide tremendous strength and greatly enhanced seismic performance to existing masonry structures.

The Helibeam System, which builds around the bonding of specially formed stainless steel HeliBars into existing masonry with a specially formulated cementitious grout, HeliBond, also offers great versatility. Available in a range of different diameters and cross-sectional areas, different combinations of HeliBars and installation patterns may be used in pursuit of a variety of different solutions. Their unique helical profile ensures that HeliBars can be bonded into slots and clearance holes cut and drilled into masonry without workmanship difficulty. Complete results of the tests will be published through a series of papers presented at various international seismic and engineering conferences and symposiums in the new year. Current results confirm that, critical to the performance of the Helibeam System is the high quality and strength of the bond created between the HeliBar reinforcement, the HeliBond, and the masonry itself. Further, results indicate a significant increase in the performance of the tested masonry wallettes when subjected to simulated seismic loads.

Helifix is looking forward to its on-going involvement with the project.

Problem and Solution. The architects behind this new development at Sydney's Mater Hospital complex envisaged a striking building encased in seamless brickwork, unspoiled by the appearance of structural components. They also envisaged a building shaped by a series of interwoven straight and curved walls, and where a variety brick types, colourings and glazings might be used to highlight different features. Grand in design, the construction process presented contractors with a number of interesting problems. One such problem was how to construct a curved brick panel above an opening such that the supporting concrete slab/lintel structure might remain completely concealed and only the full face of the coloured soffit brickwork fully visible.

After consulting Helifix, the bricklaying contractors for this project put together a clever and reliable solution.

First, the glazed, face bricks that were to be used to create the bottom edge of this panel were cut to custom sizes and shapes. Second, these cut bricks were lined up and bonded to long lengths of HeliBar with EpoxyPlus resin to enable easy on-site positioning and manipulation, and the easy formation of the curved facade lines. Third, short PatchPins were partially driven into each individual brick, leaving an exposed tie section of around 50mm extending from the back of each brick. Finally, while allowing for movement, the concrete slab/lintel was poured.

The slab has now cured, and each PatchPin now acts as a mechanical key, connecting each brick directly back to the concrete slab.

Problem and Solution.

The DryFix remedial wall tie system has been used to repair buildings at the former artillery school, Manly, NSW.

Situated atop North Head, this site plays host to a number of buildings which look out over a large parade ground and harbour views. And though military personnel are no longer housed here, boot camps, of a kind, are still the order of the day with the barracks and parade ground providing the backdrop in recent times to a popular reality television exercise and lifestyle show.

But like other buildings in the area, age and exposure to salt air has taken its toll. Some time ago, a storm that passed through the area generated wind gusts sufficient in force to bring down the gable end of one of the buildings where wall tie corrosion had compromised structural integrity.

Over the course of the last few years, buildings at the site with the same identified problem have been retied using the DryFix system. The system in all cases was chosen for its effectiveness, simplicity and ability to keep installation damage to an absolute minimum. Installation required the drilling of only 5mm diameter pilot holes.

Problem and Solution. The construction of the Olympic Village for the Sydney 2000 Olympic games was the largest project of its kind at the time. It involved the construction of an entirely new suburb, complete with its own postcode, and was designed to house more than 15000 people during the games, a further 7000 people during the Paralympics, and a whole new population of permanent residents just a few weeks after that. The project logistics were impressive, but as if this were not enough the project engineers and developers also had to contend with the site's unique topography and geology.

The land upon which the village was to be built was once deemed part of the Parramatta River estuary but was considered at the time of construction more wasteland than wetland. This conjecture was confirmed as site surveys revealed that the many thousands of buildings to be built would have to be set into foundation soils comprised of a mix of river sediment and urban and industrial infill.

The buildings themselves had in the meantime been designed to meet a range of environmentally sustainable objectives. Most buildings received solar panelling and a range of passive energy saving features. Architecturally, the buildings had been designed to project a clean and vibrant atmosphere. Building openings were designed according to a uniform flat arch design, with additional square arched pergolas and architectural features added to individualise many of the buildings.

For the project engineers, the task of combining extensive square arch design with inconsistent foundation soils brought about a particular challenge: How to cost-effectively and reliably reinforce square masonry arches to resist cracking from likely foundation movement.

Stainless steel HeliBar reinforcing was ultimately chosen as the solution to the problem, and over the course of the multi-year project several thousand 1200mm long HeliBar lengths were installed above the corners of openings in the facades of many of the new dwellings.

The installation procedure was straight-forward, and added little to the overall construction time. In accord with Helifix New Build HeliBar Detail BNB04, during construction, single lengths of HeliBar were bedded into the first brick course running above each of the selected openings, with each installed bar positioned such that half its length projected above the opening and half into the supporting pier. A second length of HeliBar was then similarly bedded into a second brick course situated higher up in the wall.

A recent curb side survey of dwellings, close to ten years after the completion of the project, revealed that masonry cracking above openings is not an issue where HeliBars were installed.

Problem and Solution. HeliBars were used to strengthen a series of intricate, shallow brick arches newly constructed along the southern face of this building in Curl Curl, Sydney, in yet another new build HeliBar application.

Here, the project architects were keen to ensure that the Roman-styled brickwork arches possess sufficient strength to carry the loadings to be generated through the extension of an elevated concrete pathway above.

To lend additional strength to the natural arching of the brick rings, parallel lengths of 6mm diameter HeliBar were bedded into the brick course running directly over the peak of each arch. Shorter lengths of 8mm HeliBar were bonded vertically into the brick rings themselves to provide further support.

Problem and Solution. Political movements are not the only source of life in Kirribilli. Building movement in some of Sydneys largest and most prestigious apartment blocks also make a contribution. On-going movement and the gradual deterioration over the years of some component elements in this apartment block, for example, resulted in the need for some substantial refurbishment and an opportunity to revamp some of its key architectural features.

Contractors were called in originally to waterproof the balconies and to refurbish them with glass balustrades so that occupants of each apartment might make the most of their spectacular harbour view. Part of this project involved using the DryFix system to stabilise the masonry around the edges of each balcony. Additional Helifix ties were then used to secure sections of the building's parapet and help control movement in its northern elevation. In this regard, the project engineers specified Helifix Repair Detail BMJ01 to secure a movement joint that was to be cut into the northern wall.

A movement joint had been cut into the lower portion of this wall some time earlier, but it was decided that the opportunity should be taken to extend the joint to run to the full height of the wall. In accordance with detail BMJ01, after cutting the joint, the contractors installed additional DryFix wall ties up either side of the cut at 300mm centres, installed sleeved HeliBar sections across the joint to allow for horizontal movement, and then sealed the joint by injecting a suitable flexible mastic.

Problem. This building occupies a commanding position at the southern end of Manly beach, Sydney, NSW. For much of the last two years, however, its spectacular outlook has been impeded by scaffolding and contractors working to carry out much needed repairs to its intricate brickwork facade. The problems that most needed to be addressed included the deterioration and failure of wall ties and the deterioration and failure of mortar joints. Both problems undoubtedly resulted from decades of exposure to Manly's sea side conditions.

Solution. The DryFix system was called upon to retie the majority of the buildings cavity brickwork. To this end, several thousand 8mm diameter DryFix ties were driven into small 5mm diameter pilot holes that had first been drilled through the face brickwork and into the inner brickwork leaf. Larger 10mm diameter DryFix ties were driven into 6mm diameter pilot holes in one section of the building where the cavity width measured around 200mm.

The ResiTie, RetroTie and StarTie systems were used in several other areas of the building where the deterioration of the brickwork was such that some rebuilding and some resin-based tying of the facade was required.