Repair Systems — 03 — Facade & External Envelope
Undercut expansion mechanical wall tie
Supplier reference for undercut expansion mechanical remedial cavity wall ties for masonry facade remediation on Class 2 strata buildings. The highest-load mechanical anchor type — requires specialist tooling and engineer specification. Compares Hilti HDA and Fischer FAZ II by mechanism, load data, and distribution.
Undercut expansion mechanical wall ties
Undercut expansion anchors are the highest-load mechanical anchor type — they drill an undercut profile in the masonry and lock into it under bearing rather than friction. They outperform all other mechanical anchor types in characteristic resistance values and provide a more ductile failure behaviour. Specialist tooling is required. These are engineer-specified products for the most demanding structural masonry anchoring applications. Structural engineer specification is mandatory.
Supplier reference
2 of 2 suppliersHilti HDA Undercut Anchor
High-load undercut anchor with keyed mechanical lock for structural masonry anchoring
Hilti HDA (High-performance Deformation-controlled Anchor) is a specialist undercut anchor that achieves significantly higher load capacity than standard wedge or sleeve expansion anchors by locking into an undercut profile drilled in the masonry.
Fischer FAZ II Undercut Anchor
High-load deformation-controlled undercut anchor for structural masonry and concrete
Fischer FAZ II is a deformation-controlled undercut anchor for high-load structural anchoring in solid masonry and concrete — an alternative to the Hilti HDA for the most demanding applications.
| Supplier | Product | Mechanism | Grade | Tooling | Load Data | Distribution | Primary Use |
|---|---|---|---|---|---|---|---|
| Hilti Australia | HDA Undercut Anchor | Undercut bearing | 316 SS | Hilti specialist kit | ETA + PROFIS | National direct | Highest-demand structural anchoring |
| Fischer Fixings | FAZ II Undercut Anchor | Undercut bearing | 316 SS | Fischer specialist kit | ETA published | National (specialist) | Very high-load masonry anchoring |
Do not confuse undercut expansion ties with:
- Wedge expansion ties — friction-based cone-wedge mechanism, lower load capacity, no specialist tooling required — listed on the wedge expansion tie page
- Sleeve torque-control ties — bolt-tightened sleeve expansion, torque-controlled, lower load capacity than undercut — listed on the sleeve torque-control tie page
- Resin anchor ties — chemical adhesive anchors — different installation mechanism, no undercutting required, suitable for softer substrates — listed on the cavity ties — resin anchor page
- Hilti HDA vs standard Hilti HSA — the HDA is an undercut anchor; the HSA-R2 is a standard sleeve anchor — do not substitute HSA for HDA in engineer-specified undercut applications
- Undercut anchors for concrete — concrete undercut anchors are not rated for masonry substrates without technical confirmation
Disclaimer
This page provides general technical information only. Undercut expansion ties require specialist tooling and are engineer-specified for the highest-demand applications only. Anchor type, diameter, embedment, and spacing must be confirmed by a structural engineer against project-specific masonry conditions and AS 3700.