Tying scaffold to a cavity brick wall is more involved than tying to a solid masonry or timber-framed wall. Because the outer leaf of a cavity brick wall is typically only 90–110 mm thick with an air gap behind it, standard through-bolts can't simply be driven in anywhere — you need the right anchor type, the right location, and the right technique to keep both the scaffold and the wall safe.
Why Cavity Brick Walls Need Special Attention
A cavity brick wall consists of two separate leaves of brickwork (or brick and block) separated by a gap, usually 50–100 mm wide. The outer leaf carries its own weight but is not a solid mass you can anchor into freely. Driving a standard anchor into the cavity zone, or into a mortar joint without the correct fitting, risks cracking or dislodging bricks, which can compromise the wall's structural integrity and create a serious falling hazard on site.
WorkSafe NZ requires that all scaffolding is erected, altered, and dismantled by or under the direct supervision of a competent person, and that ties are designed and installed to safely transfer the loads imposed by the scaffold into the structure.
Types of Ties Used on Cavity Brick Walls
There are three main tie methods suited to cavity brick construction:
1. Through-the-Wall Ties (Box Ties)
A box tie (also called a reveal tie or through-wall tie) passes a scaffold tube or fitting through a window or door opening and bears against the inside of the reveals. This is often the preferred method because it avoids drilling into the brickwork altogether. The tube is wedged firmly across the opening, and the scaffold is connected to it with a right-angle coupler.
- Best used where window or door openings are accessible
- No drilling required — no risk of brick damage
- The opening must be strong enough to take the load; check with the building owner or a structural engineer if in doubt
2. Anchor Bolt Ties (Drilled Fixings)
Where box ties aren't practical, mechanical anchor bolts or chemical anchors can be drilled into the mortar joints or into the brick itself. Key points:
- Always drill into mortar joints where possible — mortar is easier to repair and the brick face is preserved
- Use anchors rated for the pull-out and shear loads your scaffold design requires
- The anchor must reach into the inner leaf or be specifically rated for the outer leaf thickness — check the manufacturer's load data
- Sika and Mapei both supply chemical anchor systems with published load ratings for masonry; always follow the product's technical data sheet
- After the scaffold is struck, holes must be made good with a matching mortar or sealant to maintain the wall's weathertightness (important under NZ Building Code clause E2 – External Moisture)
3. Prop-Out Ties
A prop-out tie uses a tube braced from inside the building, pushing outward against the wall to create a reaction point. This avoids drilling but requires access to the interior and a suitable internal structure to brace against. It is less common but useful in heritage or sensitive buildings.
Tie Spacing and Load Requirements
Scaffold tie spacing must follow your scaffold design or, where a design isn't required, the guidance in the relevant standard. In New Zealand, scaffolding is generally referenced against AS/NZS 1576 (Scaffolding) and AS/NZS 4576 (Guidelines for Scaffolding). Typical tie spacing for a façade scaffold is:
| Direction | Maximum Spacing (general guide) |
|---|---|
| Vertical | Every second lift (approx. 4 m) |
| Horizontal | Every 6 m along the face |
These are general starting points only. Your actual tie pattern must match the scaffold design or the manufacturer's specification. For taller or more complex scaffolds, a site-specific engineering design is required — check with MBIE Building Performance for consent requirements.
Protecting the Wall During and After Scaffold
- Use rubber or plastic buffer pads where scaffold tubes bear against brickwork to prevent spalling
- Inspect ties regularly during the scaffold's life, especially after high winds — New Zealand's variable climate means wind loads can be significant
- When striking the scaffold, remove anchors carefully and repair all penetrations promptly to prevent moisture ingress, which is a key concern under the NZ Building Code
- If the wall has a cavity membrane or DPC (damp-proof course), take care not to bridge or damage it when drilling
Building Consent Considerations
Erecting scaffold itself generally doesn't require a building consent under Schedule 1 of the Building Act, but always confirm with your local council — rules can vary, particularly for scaffolding on heritage buildings or in special character zones. Any structural repairs to the wall triggered by anchor damage may require consent.
When to Call a Professional
Scaffolding is not a DIY task. Under the Health and Safety at Work Act 2015 and WorkSafe NZ guidelines, scaffolding over 5 m in height must be erected, altered, and dismantled by a certificated scaffolder (or under their direct supervision) — confirm the exact requirements with WorkSafe NZ, as rules vary with scaffold type and complexity. Tying into a cavity brick wall adds another layer of complexity that demands experience and, in many cases, an engineering assessment.
If you're unsure whether your wall can safely accept the tie loads, engage a structural engineer before work begins. For the scaffolding itself, find a qualified local scaffolding professional on tradedirectory.co.nz who has experience with masonry buildings.
