Yes, using timber packing — more correctly called sole boards or sole plates — under scaffold base plates on soft or uneven ground is standard, accepted practice in New Zealand scaffolding. However, there are specific requirements around timber size, condition, and placement that must be followed to keep the structure safe and compliant.
Why Base Plates Need Support on Soft Ground
Scaffolding transfers significant loads down through its standards (vertical tubes) into the ground via base plates — the flat steel feet at the bottom of each standard. On firm, compacted ground, base plates alone may be adequate. On soft, wet, or disturbed ground — common on NZ building sites after rain — the base plate can sink or tilt, causing the entire scaffold to become unstable.
A sole board spreads the point load from the base plate over a larger surface area, reducing ground pressure and preventing settlement. Think of it like a snowshoe: the same weight, spread over more area, stops you sinking in.
What Timber Should You Use?
Not just any scrap timber will do. The following are the generally accepted minimum requirements in NZ trade practice:
- Species and grade: Use structural-grade timber — H3 treated pine is commonly used for ground contact. Avoid untreated, rotten, split, or heavily knotted timber.
- Thickness: A minimum of 50 mm thick is the widely accepted standard. Thinner boards can split or crush under load.
- Width: Typically 200–225 mm wide (a standard 200 × 50 framing timber is commonly used).
- Length: Long enough to support at least two base plates where standards are closely spaced, or a minimum of around 450–600 mm under a single base plate.
- Condition: The timber must be free of decay, large knots, splits, or damage. Inspect it before every use.
| Requirement | Minimum Guideline |
|---|---|
| Thickness | 50 mm |
| Width | 200 mm |
| Length (single base plate) | ~450–600 mm |
| Timber grade | Structural / H3 treated |
| Condition | No rot, splits, or major defects |
How to Place Sole Boards Correctly
Placement matters just as much as the timber itself:
- Level the ground first where possible — remove loose fill, rocks, or debris.
- Lay the sole board flat on firm, undisturbed ground. Never place it on loose fill, rubble, or over voids.
- Centre the base plate on the sole board so the load is distributed evenly. The base plate should not overhang the edge of the timber.
- Use adjustable base plates (screw jacks) to fine-tune the height and keep standards plumb. Sole boards are not a substitute for proper levelling.
- Check regularly — especially after rain. Soft NZ soils can shift overnight, and a sole board that was level on Monday may have settled by Wednesday.
Ground Conditions That Need Extra Attention
Some ground conditions require more than a standard sole board:
- Very soft or waterlogged ground: Consider wider or longer sole boards, or doubling up the thickness. In some cases, ground improvement (compaction, gravel fill) is needed before erecting scaffold.
- Sloped sites: Common in hilly NZ suburbs. Adjustable base jacks combined with sole boards are essential. Steep slopes may require engineered scaffold design.
- Made ground or fill: Ground that has been recently filled or disturbed may have unpredictable bearing capacity. Get advice from a licensed scaffolder or engineer.
- Near excavations or trenches: Never place scaffold loads close to the edge of an excavation without engineering input.
Safety and Legal Requirements in New Zealand
Scaffolding safety in New Zealand is governed by WorkSafe NZ, and the relevant standard is NZS 4576 – Guidelines for Scaffolding Safety. Employers and those in control of a worksite have duties under the Health and Safety at Work Act 2015 to ensure scaffolding is erected, used, and dismantled safely.
Scaffolding over 5 metres in height must be erected, altered, or dismantled by — or under the direct supervision of — a certificated scaffolder. This is a legal requirement under the Health and Safety at Work (General Risk and Workplace Management) Regulations 2016. Even for lower scaffolding, if you are not experienced, the risks of getting it wrong are serious.
Always ensure:
- A scaffold handover certificate is completed before use (required for scaffolding over 5 m).
- The scaffold is inspected regularly, especially after adverse weather.
- No unauthorised modifications are made once the scaffold is erected.
When to Call a Professional
While a competent homeowner might assist with minor low-level scaffold tasks, erecting scaffolding — including setting up base plates and sole boards correctly — is skilled, safety-critical work. You should always engage a licensed, certificated scaffolder if:
- The scaffold will exceed 5 metres in height.
- The ground conditions are soft, sloped, waterlogged, or uncertain.
- The scaffold is near an excavation, retaining wall, or unstable ground.
- You are unsure about load calculations or tie requirements.
- The scaffold will be used by workers (not just yourself).
You can find qualified local scaffolders on tradedirectory.co.nz. Getting it right from the start is far cheaper than dealing with a collapse.
