A reciprocating saw can absolutely be used to cut through thick tree roots, and it's actually one of the most popular tools for the job among both DIYers and tradespeople. That said, success depends on using the right blade, understanding the risks to the tree, and knowing when the job is beyond a DIY approach. Here's what you need to know before you start.
Why a Reciprocating Saw Works Well for Roots
A reciprocating saw (sometimes called a recip saw or by the brand name Sawzall) is well suited to root cutting because its long, aggressive blade can reach into confined spaces — like a trench, under a deck, or alongside a foundation — where a chainsaw or handsaw simply won't fit. The back-and-forth cutting action handles the fibrous, often dirt-caked nature of roots reasonably well, provided you choose the correct blade.
Choosing the Right Blade
This is the single most important factor. Standard wood-cutting blades will blunt almost instantly when they hit soil, grit, or stones embedded in or around roots.
- Bi-metal demolition blades (typically 150–300 mm long, 3–6 TPI) are the go-to choice. They're tough enough to handle the occasional knock against soil or rock.
- Carbide-tipped blades last significantly longer in dirty, gritty conditions and are worth the extra cost for larger jobs.
- Avoid fine-toothed blades designed for metal or finish timber — they clog and overheat quickly.
- Have several spare blades on hand. Root cutting is hard on blades, and a dull blade is both inefficient and dangerous.
You'll find a good range of demolition and bi-metal blades at Bunnings and Mitre 10.
Preparing the Work Area
Before you cut, expose the root properly:
- Dig around the root with a spade or mattock to clear at least 100–150 mm of soil away from the cutting zone. This protects your blade and reduces the risk of the saw kicking back when it hits hidden rocks.
- Hose the root down to wash away loose grit — this alone can double blade life.
- Mark your cut line clearly, especially if you're working near a foundation or other services.
⚠️ Important: Before any digging, call Dial Before You Dig (0800 248 344) or visit their website to identify underground services — water pipes, gas lines, and electrical cables can all run near tree roots. Striking a buried service is extremely dangerous.
Safety First
Working with a reciprocating saw around roots carries real risks. Follow these precautions:
- Wear safety glasses or goggles, heavy-duty gloves, steel-capped boots, and hearing protection.
- Keep bystanders — especially children — well clear of the work area.
- Maintain a firm two-handed grip on the saw at all times; roots can grab the blade and cause sudden kickback.
- Never operate a reciprocating saw in a waterlogged trench or in wet conditions where electrical hazards exist.
- Check your saw's power cord (if corded) is well away from the cutting path. A cordless saw is often safer in confined trenches.
For general power tool safety guidance, WorkSafe NZ is a useful resource.
Will Cutting Roots Harm the Tree?
This is where many homeowners underestimate the impact of root work. Cutting roots — even with the best intentions — can:
- Destabilise the tree, making it a hazard in wind. Large roots on one side of the trunk are often structural anchors.
- Stress or kill the tree, particularly if roots within the drip line (the area beneath the canopy) are severed.
- Create entry points for fungal disease and rot.
As a rough guide, avoid cutting any root closer to the trunk than 3–5 times the trunk diameter. So for a tree with a 200 mm diameter trunk, don't cut roots within roughly 600 mm–1 m of the base. However, this varies by species and tree health, so if you're unsure, get an arborist's assessment first.
Thick Roots: When Is It Too Much for DIY?
| Root diameter | DIY with recip saw? | Notes |
|---|---|---|
| Up to ~50 mm | Generally fine | Standard bi-metal blade, clear the soil first |
| 50–100 mm | Possible but harder | Use carbide blade, may need multiple passes |
| 100–200 mm | Challenging | Consider a chainsaw or arborist |
| Over 200 mm | Call a professional | Risk of destabilising the tree is significant |
For large, mature trees — particularly those near your house, a fence, or a neighbouring property — it's strongly advisable to engage a qualified arborist. They can assess whether root removal is safe, advise on tree health, and carry out the work with the right equipment. You can find local arborists on tradedirectory.co.nz.
Council Rules and Protected Trees
In New Zealand, many councils have tree protection rules in their District Plans. Some trees — particularly large or heritage specimens — may require a resource consent before any root or branch work is carried out. Check with your local council before starting work on any significant tree. MBIE Building Performance can also provide guidance on where building work intersects with tree root removal (for example, near foundations).
When to Call a Professional
Call a qualified arborist if:
- The tree is large, mature, or visibly stressed.
- Roots are close to the trunk or within the drip line.
- The tree is protected under your council's District Plan.
- Roots are damaging a foundation, retaining wall, or drainage system (you may also need a plumber or builder involved).
- You're not confident about the stability of the tree after cutting.
- The root system is extensive and the job is beyond a single afternoon's work.
A professional arborist will have the training, insurance, and equipment to do the job safely and in the best interests of the tree and your property.
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