A freestanding scaffold tower that wobbles is not just annoying — it is genuinely dangerous. The good news is that most instability comes from a handful of fixable causes: missing or incorrectly fitted braces, unlocked castors, or a tower that is simply too tall for its base width. Sorting these out before you climb is essential, and in New Zealand, working safely at height is governed by WorkSafe NZ regulations that place real obligations on anyone erecting or using a scaffold.
Understand Why Towers Wobble
Before you start adding braces, it helps to know what causes instability in the first place:
- Incorrect height-to-base ratio — the most common cause. A tower that is too tall relative to its base footprint will always feel unstable.
- Missing diagonal braces — scaffold frames rely on triangulation to resist racking (side-to-side movement).
- Unlocked or worn castors — mobile towers must have all castors locked when in use.
- Uneven ground — a tower on a slope or soft ground will shift under load.
- Loose couplers or pins — components that are not fully engaged allow movement at every joint.
Check the Height-to-Base Ratio First
This is the single most important stability rule. As a general guide for mobile aluminium scaffold towers used in NZ:
| Condition | Maximum height-to-base ratio |
|---|---|
| Indoors (sheltered) | 4:1 |
| Outdoors (exposed to wind) | 3.5:1 |
So if your tower base measures 1.5 m wide, the working platform height should not exceed 6 m indoors or 5.25 m outdoors. Always check the manufacturer's manual for your specific tower — these figures can vary. If you have exceeded the ratio, you must either widen the base using outriggers or reduce the height.
Fit Outriggers (Stabilisers)
Outriggers are fold-out or bolt-on arms that extend the effective base width of the tower without adding height. Most aluminium modular tower systems (such as those available from Bunnings or Mitre 10) include outrigger kits as an accessory.
- Fit outriggers to all four corners of the tower base.
- Adjust the feet so all four outrigger pads sit firmly on the ground — use a spirit level to check.
- On soft ground, place a timber sole board (at least 200 mm wide) under each foot to spread the load.
- Once outriggers are fitted, re-check your height-to-base ratio using the new, wider base measurement.
Install All Diagonal Braces Correctly
Diagonal braces are what give a scaffold tower its rigidity. Without them, the frame can rack like a parallelogram under side load.
- Fit braces at every bay — do not skip intermediate levels.
- Braces should run from corner to corner of each frame panel, forming an X or a Z pattern depending on the system.
- Ensure every brace pin or clip is fully engaged and locked. Give each one a firm tug after fitting.
- On taller towers, fit horizontal braces (ledger braces) at the mid-height point as well as top and bottom.
Lock All Castors and Check the Ground
If your tower is mobile (on wheels):
- Lock every castor before anyone climbs the tower. Most castors have a foot-operated lever — press it down firmly.
- Check that castors are not cracked or seized. Damaged castors must be replaced before use.
- Never move a tower with anyone on it — this is a WorkSafe requirement, not just good practice.
- On uneven ground, consider using a fixed-base tower with adjustable screw feet rather than castors.
Tie the Tower to the Structure Where Possible
Where your work allows it, tying the tower to a solid structure is the most effective way to eliminate wobble on taller towers. Use proprietary scaffold ties or tube-and-coupler connections to attach the tower to a wall, column or other fixed point at regular intervals (check the manufacturer's guide for spacing, but every 4 m of height is a common starting point).
- Use only purpose-made scaffold couplers — never rope, wire or cable ties.
- The tie point on the building must be structurally sound. Do not tie to gutters, downpipes or lightweight cladding.
- If you cannot tie to the structure, outriggers become even more critical.
Inspect Before Every Use
Get into the habit of a quick pre-use check:
- All frames, braces and platforms fully engaged and locked.
- Castors locked (if mobile).
- Outrigger feet all in contact with the ground.
- No visible damage, bent tubes or cracked welds.
- Platform guardrails and toe boards fitted at working height.
BRANZ and WorkSafe both recommend a formal inspection record for any scaffold used on a construction site.
When to Call a Professional
Under New Zealand law, **scaffolding over a certain height may require involvement of a competent person in certain contexts, and more complex scaffolding must be designed, erected and inspected by a competent person — which in practice means a qualified scaffolder. If your tower:
- Exceeds 5 m platform height,
- Is being used on a construction site,
- Requires complex ties or is on difficult ground,
- Or you are simply not confident it is stable,
…then stop and get a licensed scaffolder involved. You can find qualified local scaffolders on tradedirectory.co.nz. It is also worth checking MBIE Building Performance for guidance on when scaffolding requires a building consent or a licensed practitioner.
For workplace use, your employer has duties under the Health and Safety at Work Act 2015 — WorkSafe NZ publishes specific guidance on working at height that is worth reading before any scaffold is erected.
