Placing scaffold feet in a garden near trees is one of those jobs that looks straightforward but can cause serious, long-lasting damage if you get it wrong. Tree roots — especially the fine feeder roots that absorb water and nutrients — are far more widespread and shallow than most people realise, and compaction or physical damage from scaffold bases can stress or even kill an established tree. With a bit of planning, though, you can protect your trees and still get the scaffold safely in place.
Understand How Tree Roots Spread
A common misconception is that tree roots mirror the canopy above ground. In reality, roots often extend two to three times the canopy radius outward, and the most active feeder roots sit in the top 300–600 mm of soil. This means even scaffold feet placed well outside the visible drip line can still be sitting on important root zones. Before you position anything, take a moment to map out where the roots are likely to be.
Assess the Risk Before You Start
Not all trees are equally sensitive. Factors that increase risk include:
- Species: Some trees (e.g. pohutukawa, kauri, magnolia) are particularly sensitive to root disturbance.
- Age and size: Mature trees have more to lose but are also sometimes more resilient; young trees can be set back significantly.
- Soil type: Heavy clay soils (common in many NZ regions) compact more easily than free-draining sandy soils.
- Existing stress: A tree already dealing with drought, disease, or previous construction work is more vulnerable.
If you have a large, mature, or heritage tree on your property, consider getting an arborist assessment before work begins. Some councils in New Zealand have tree protection rules in their district plans, and damaging a protected tree — even unintentionally during building work — can result in enforcement action. Check with your local council before proceeding.
Practical Steps to Protect Tree Roots
1. Spread the Load
The biggest threat from scaffold feet is soil compaction, which squeezes air and water out of the soil and suffocates roots. The standard scaffold base plate (typically around 150 × 150 mm) concentrates a lot of weight on a small area. To spread the load:
- Place scaffold boards or thick plywood sheets (at least 18–25 mm structural ply) under the base plates. Aim for a sheet that covers at least 600 × 600 mm per foot, or ideally a continuous run of boards.
- Use scaffold sole boards — these are purpose-made timber pads used by professional scaffolders to distribute load. Your scaffolder should have these as standard.
- Avoid using single bricks or pavers, which can crack and still concentrate load.
2. Avoid Cutting or Trenching Through Root Zones
Never dig trenches or drive stakes through a root zone to anchor scaffold. If tie-backs or anchors are needed, discuss alternative fixing methods with your scaffolder — for example, anchoring to the building structure rather than the ground.
3. Protect the Soil Surface
Before laying boards, consider placing a layer of wood chip mulch (100–150 mm deep) over the root zone first. This cushions the soil, retains moisture, and reduces compaction. It also makes it easier to restore the area afterwards. Avoid plastic sheeting, which cuts off oxygen to the roots.
4. Limit Traffic in the Root Zone
Scaffold feet are only part of the problem — foot traffic and wheelbarrow runs over the same area repeatedly will compound compaction. If possible:
- Define a clear access path away from the root zone.
- Use temporary ground protection panels (available from hire companies) if heavy traffic is unavoidable.
5. Keep the Duration as Short as Possible
The longer scaffold sits on a root zone, the greater the cumulative impact. Plan your work schedule so the scaffold is up only as long as genuinely needed.
6. Restore the Area After Removal
Once the scaffold comes down, gently aerate the soil with a garden fork (avoid deep digging), top up with compost or mulch, and water well. This helps the root zone recover. If you notice the tree looking stressed — yellowing leaves, dieback, or wilting — consult a qualified arborist.
What About Building Consent?
Most residential scaffolding for maintenance or repair work falls under Schedule 1 of the Building Act as exempt work, meaning a building consent is not required. However, this depends on the scope of the project. Always confirm with your local council whether consent is needed for your specific job. You can find guidance at MBIE Building Performance.
Safety Note
Scaffolding must be erected, altered, and dismantled safely. Under the Health and Safety at Work Act 2015, scaffolding over a certain height requires a certified scaffolder — check current WorkSafe NZ guidance for the applicable threshold. Even for lower heights, poorly erected scaffold is a serious fall hazard. WorkSafe NZ has clear guidance on scaffolding requirements for both workers and homeowners.
When to Call a Professional
You should always use a licensed, experienced scaffolder for erecting scaffold — this is not a DIY job. A good scaffolder will already know how to position base plates and sole boards correctly, but it's worth raising your tree concerns with them explicitly before work starts. If you have a large, protected, or heritage tree nearby, bring in a qualified arborist to advise on root protection zones before the scaffold goes up. You can find local scaffolders and arborists on tradedirectory.co.nz.
